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O� '

GEOLOGICAL HISTORY OF PI, A NTS

PEEFAOE

The object of tbis work is to give, in a connected form, a summary of tbe development of the vegetablenbsp;kingdom in geological time.

To the geologist and botanist the subject is one of importance with reference to their special pursuits, andnbsp;one on which it has not been easy to find any convenient manual of information. It is hoped that its treat-ment in the present volume will also be found sufficiently simple and popular to be attractive to thenbsp;general reader.

In a work of so limited dimensions, detailed descriptions cannot be given, except occasionally by way of illustration; but references to authorities will be madenbsp;in foot-notes, and certain details, which may be useful tonbsp;collectors and students, will be placed in notes appendednbsp;to the chapters, so as not to encumber the text.

The illustrations of this work are for the most part original; but some of them have previously appearednbsp;in special papers of the author.

OO�^TENTS.

CHAPTER I.

CHAPTER II.

CHAPTER III.

Age of Acrogens and Gymnosperms . nbsp;nbsp;nbsp;.nbsp;nbsp;nbsp;nbsp;.nbsp;nbsp;nbsp;nbsp;.nbsp;nbsp;nbsp;nbsp;.45

CHAPTER IV.

CHAPTER V.

CHAPTER VI.

The Reign of Angiosperms in the Later Cretaceous and Early Tertiary or Kainozoic........191

LIST OF ILLTJSTRATIOFTS.

Table of Chronology of Plants . Protaunularia HarknossUnbsp;Nematophytou Logani (three Figures)nbsp;Trail of King-Crah .nbsp;nbsp;nbsp;nbsp;�nbsp;nbsp;nbsp;nbsp;-nbsp;nbsp;nbsp;nbsp;�

Ptilophyton (two Figures) Psilophyton (two Figures)nbsp;Sphenophyllumnbsp;Lepidodendronnbsp;Various Fernsnbsp;Archaeopterisnbsp;Caulopterisnbsp;Megalopterisnbsp;Calamitesnbsp;Asterophyllitesnbsp;Dadoxylon

geological history of plants.

fEELIHIKABY IDEAS OF GEOLOGICAL CHBOHOLOGT AUD OF THE CLASSIFICATIOSr OF PLAHTS.

The knowledge of fossil plants and of the history of the vegetable kingdom has, until recently, been so frag-�entary that it seemed hopeless to attempt a detailednbsp;treatment of the subject of this little book. Our storesnbsp;of knowledge have, however, been rapidly accumulatingnbsp;iQ recent years, and we have now arrived at a stage whennbsp;every new discovery serves to render useful and intelligi-ble a Vast number of facts previously fragmentary and ofnbsp;uncertain import.

The writer of this work, born in a district rich in fossil plants, began to collect and work at these as anbsp;in connection with botanical and geological pursuits.nbsp;He has thus been engaged in the study of fossil plantsnbsp;for nearly half a century, and, while he has publishednbsp;much on the subject, has endeavoured carefully to keepnbsp;Within the sphere of ascertained facts, and has made itnbsp;u specialty to collect, as far as possible, what has beennbsp;published by others. He has also enjoyed opportunitiesnbsp;uf correspondence or personal intercourse with most of

the more eminent workers in the subject. Now, in the evening of his days, he thinks it right to endeavour tonbsp;place before the world a summary of facts and of his ownnbsp;matured conclusions�feeling, however, that nothing cannbsp;be final in this matter; and that he can only hope tonbsp;sketch the present aspect of the subject, and to point thenbsp;way to new developments, which must go on long afternbsp;he shall have passed away.

The subject is one which has the disadvantage of presupposing some knowledge of the geological history of the earth, and of the classification and structures of modern plants ; and in order that all who may please to readnbsp;the following pages may be placed, as nearly as possible,nbsp;on the same level, this introductory chapter will be devoted to a short statement of the general facts of geologicalnbsp;chronology, and of the natural divisions of the vegetablenbsp;kingdom in their relations to that chronology.

The crust of the earth, as we somewhat modestly term that portion of its outer shell which is open to our observation, consists of many beds of rock superimposed onnbsp;each other, and which must have been deposited successively, beginning with the lowest. This is proved by thenbsp;structure of the beds themselves, by the markings onnbsp;their surfaces, and by the remains of animals and plantsnbsp;which they contain ; all these appearances indicating thatnbsp;each successive bed must have been the surface before itnbsp;was covered by the next.

As these beds of rock were mostly formed under water, and of material derived from the waste of land, they arenbsp;not universal, but occur in those places where there werenbsp;extensive areas of water receiving detritus from the land.nbsp;Further, as the distinction of land and water arises primarily from the shrinkage of the mass of the earth, andnbsp;from the consequent collapse of the crust in some placesnbsp;and ridging of it up in others, it follows that there have,nbsp;from the earliest geological periods, been deep ocean-

basins, ridges of elevated land, and broad plateaus inter-�vening between the ridges, and which were at some times Under water, and at other times land, with many inter-uiediate phases. The settlement and crumpling of thenbsp;crust were not continuous, but took place at intervals;nbsp;and each such settlement produced not only a ridging upnbsp;along certain lines, but also an emergence of the plainsnbsp;or plateaus. Thus at all times there have been ridges ofnbsp;folded rock constituting mountain-ranges, flat expansionsnbsp;of continental plateau, sometimes dry and sometimes submerged, and deep ocean-basins, never except in some ofnbsp;their shallower portions elevated into land.

By the study of the successive beds, more especially of those deposited in the times of continental submergence, we obtain a table of geological chronology whichnbsp;expresses the several stages of the formation of the earth�snbsp;crust, from that early time when a solid shell first formednbsp;on our nascent planet to the present day. By collectingnbsp;fbe fossil remains embedded in the several layers andnbsp;placing these in chronological order, we obtain in likenbsp;manner histories of animal and plant life parallel to thenbsp;physical changes indicated by the beds themselves. Thenbsp;fects as to the sequence we obtain from the study of exposures in cliffs, cuttings, quarries, and mines; and bynbsp;oorrelating these local sections in a great number of places,nbsp;�''�c obtain our general table of succession ; though it is tonbsp;be observed that in some single exposures or series ofnbsp;exposures, like those in the great cahons of Colorado, ornbsp;on the coasts of Creat Britain, we can often in one localitynbsp;�ee nearly the whole sequence of beds. Let us observenbsp;here also that, though we can trace these series of depositsnbsp;over the whole of the surfaces of the continents, yet ifnbsp;fhe series could be seen in one spot, say in one shaft sunknbsp;through the whole thickness of the earth�s crust, thisnbsp;Would be sufficient for our purpose, so far as the historynbsp;of life is concerned.

The evidence is similar to that obtained by Schlie-mann on the site ot Troy, where, in digging through successive layers of debris, he found the objects deposited by successive occupants of the site, from the time of thenbsp;Roman Empire back to the earliest tribes, whose flintnbsp;weapons and the ashes of their fires rest on the originalnbsp;surface of the ground.

Let us now tabulate the whole geological succession with the history of animals and plants associated with it:

It will be observed, since only the latest of the systems of formations in this table belongs to the period of human history, that the whole lapse of time embraced innbsp;the table must be enormous. If we suppose the modernnbsp;period to have continued for say ten thousand years, andnbsp;each of the others to have been equal to it, we shall require two hundred thousand years for the whole. Therenbsp;is, however, reason to believe, from the great thickness ofnbsp;the formations and the slowness of the deposition of many

them in the older systems, that they must have required vastly greater time. Taking these criteria into account, it has been estimated that the time-ratios fornbsp;the first three great ages may be as one for the Kainozoionbsp;to three for the Mesozoic and twelve for the Palaeozoic,nbsp;'V'ith as much for the Eozoic as for the Palaeozoic. This isnbsp;Dana�s estimate. Another, by Hull and Houghton, givesnbsp;the following ratios : Azoic, 34�3 per cent. ; Palffiozoic,nbsp;43'5 per cent.; Mesozoic and Kainozoic, 33�3 per cent.nbsp;It is further held that the modern period is much shorternbsp;than the other periods of the Kainozoio, so that ournbsp;geological table may have to be measured by millions ofnbsp;years instead of thousands.

We cannot, however, attach any certain and definite Value in years to geological time, but must content ourselves with the general statement that it has been vastlynbsp;leug in comparison to that covered by human history.

Bearing in mind this great duration of geological time, and the fact that it probably extends from a period whennbsp;Die earth was intensely heated, its crust thin, and its continents as yet unformed, it will be evident that the con-�litious of life in the earlier geologic periods may havenbsp;been very different from those which obtained later.nbsp;iVhen we further take into account the vicissitudes ofnbsp;land and water which have occurred, we shall see thatnbsp;such changes must have produced very great differencesnbsp;nf climate. The warm equatorial waters have in allnbsp;periods, as superficial oceanic currents, been main agentsnbsp;in the diffusion of heat over the surface of the earth, andnbsp;their distribution to north and south must have beennbsp;determined mainly by the extent and direction of land,nbsp;though it may also have been modified by the changes innbsp;ihe astronomical relations and period of the earth, andnbsp;ihe form of its orbit.¹ We know by the evidence of

fossil plants that changes of this kind have occurred so great as, on the one hand, to permit the plants of warmnbsp;temperate regions to exist within the Arctic Circle; and,nbsp;on the other, to drive these plants into the tropics andnbsp;to replace them by Arctic forms. It is evident also thatnbsp;in those periods when the continental areas were largelynbsp;submerged, there might be an excessive amount of moisture in the atmosphere, greatly modifying the climate, innbsp;so far as plants are concerned.

Let us now consider the history of the vegetable kingdom as indieated in the few notes in the right-hand column of the table.

The most general subdivision of plants is into the two great series of Cryptogams, or those which have no manifest flowers, and produce minute spores instead of seeds ;nbsp;and Phsenogams, or those which possess flowers and produce seeds containing an embryo of the future plant.

1. nbsp;nbsp;nbsp;Thallogens, cellular plants not distinctly distinguishable into stem and leaf. These are the Fungi, thenbsp;Liehens, and the Algae, or sea-weeds.

2. nbsp;nbsp;nbsp;Anogens, having stem and foliage, hut wholly cellular. These are the Mosses and Liverworts.

3. nbsp;nbsp;nbsp;Acrogens, which have long tubular fibres as well asnbsp;cells in their composition, and thus have the capacity ofnbsp;attaining a more considerable magnitude. These are thenbsp;Ferns {Filices), the Mare�s-tails {Equisetacem), and thenbsp;Club-mosses {Lycopodiacem), and a curious little groupnbsp;of aquatic plants called Ehizocarps {RMzocarpece).

The PliEenogams are all vascular, but they differ much in the simplicity or complexity of their flowers or seeds.nbsp;On this ground they admit of a twofold division :

1. Gymnosperms, or those which bear naked seeds not enclosed in fruits. They are the Pines and theirnbsp;allies, and the Cycads.

3. Angiosperms, which produce true fruits enclosing the seeds. In this group there are two well-marked sub-lt;livisions differing in the structure of the seed and stem.nbsp;They are the Endogens, or inside growers, with seeds having one seed-leaf only, as the grasses and the palms; andnbsp;the Exogens, having outside-growing woody stems, andnbsp;seeds with two seed-leaves. Most of the ordinary forest-trees of temperate climates belong to this group.

On referring to the geological table, it will be seen that there is a certain rough correspondence between thenbsp;order of rank of plants and the order of their appearancenbsp;in time. The oldest plants that we certainly know arenbsp;^Igae, and with these there are plants apparently withnbsp;the structures of Thailophytes but the habit of trees, andnbsp;which, for want of a better name, I may call Protogens.nbsp;Plants akin to the Ehizocarps also appear very early.nbsp;Next in order we find forests in which gigantic Ferns andnbsp;Tycopods and Mare�s-tails predominate, and are associatednbsp;with pines. Succeeding these we have a reign of Gym-nosperms, and in the later formations we find the highernbsp;Phsenogams dominant. Thus there is an advance innbsp;elevation and complexity along with the advance innbsp;geological time, but connected with the remarkable factnbsp;tliat in earlier times low groups attain to an elevationnbsp;nnexampled in later times, when their places are occupied with plants of higher type.

It is this historical development that we have to trace in the following pages, and it will be the most simplenbsp;nnd at the same time the most instructive method tonbsp;oonsider it in the order of time.

Oldest of all the formations known to geologists, and representing perhaps the earliest rocks produced after ournbsp;earth had ceased to he a molten mass, are the hard, crystalline, and much-contorted rocks named by the late Sirnbsp;W. E. Logan Laurentian, and which are largely developednbsp;in the northern parts of N'orth America and Europe, andnbsp;in many other regions. So numerous and extensive, indeed, are the exposures of these rocks, that we have goodnbsp;reason to believe that they underlie all the other formations of our continents, and are even world-wide in theirnbsp;distribution. In the lower part of this great system ofnbsp;rocks which, in some places at least, is thirty thousandnbsp;feet in thickness, we find no traces of the existence ofnbsp;any living thing on the earth. But, in the middle portion of the Laurentian, rocks are found which indicatenbsp;that there were already land and water, and that the watersnbsp;and possibly the land were already tenanted by livingnbsp;beings. The great beds of limestone which exist in thisnbsp;part of the system furnish one indication of this. In thenbsp;later geological formations the limestones are mostly organic�that is, they consist of accumulated remains ofnbsp;shells, corals, and other hard parts of marine animals,nbsp;which are composed of calcium carbonate, which the animals obtain directly from their food, and indirectly fromnbsp;the calcareous matter dissolved in the sea-water. In like

Dianner great beds of iron-ore exist in the Lanrentian; but in later formations the determining cause of thenbsp;accumulation of such beds is the partial deoxidation andnbsp;solution of the peroxide of iron by the agency of organicnbsp;matter. Besides this^ certain forms known as Eozoonnbsp;Ganadense have been recognised in the Lanrentian limestones, which indicate the presence at least of one of thenbsp;lower types of marine animals. Where animal life is, wenbsp;may fairly infer the existence of vegetable life as well,nbsp;since the plant is the only producer of food for the ani-But we are not left merely to this inference. Greatnbsp;quantities of carbon or charcoal in the form of the substance known as graphite or plumbago exist in thenbsp;Lanrentian. Now, in more recent formations we havenbsp;deposits of coal and bituminous matter, and we knownbsp;that these have arisen from the accumulation and slownbsp;putrefaction of masses of vegetable matter. Further, innbsp;places where igneous action has affected the beds, wenbsp;dud that ordinary coal has been changed into anthracitenbsp;and graphite, that bituminous shales have been convertednbsp;into graphitic shales, and that cracks filled with softnbsp;bituminous matter have ultimately become changed intonbsp;''^eins of graphite. When, therefore, we find in the Lau-'�entian thick beds of graphite and beds of limestonenbsp;charged with detached grains and crystals of this substance, and graphitic gneisses and schists and veins ofnbsp;graphite traversing the beds, we recognise the samenbsp;phenomena that are apparent in later formations containing vegetable debris.

The carbon thus occurring in the Lanrentian is not to be regarded as exceptional or rare, but is widely distributed and of large amount. In Canada more especiallynbsp;the deposits are very considerable.

The graphite of the Lanrentian of Canada occurs both iu beds and in veins, and in such a manner as to shownbsp;that its origin and deposition are contemporaneous with

those of the containing rock. Sir William Logan states ¹ that � the deposits of plumbago generally occur in thenbsp;limestones or in their immediate vicinity, and granularnbsp;varieties of the rock often contain large crystalline platesnbsp;of plumbago. At other times this mineral is so finelynbsp;disseminated as to give a bluish-grey colour to the limestone, and the distribution of bands thus coloured seemsnbsp;to mark the stratification of the rock.� He furthernbsp;states: � The plumbago is not confined to the limestones ; large crystalline scales of it are occasionally disseminated in pyroxene rock, and sometimes in quartzitenbsp;and in feldspathic rocks, or even in magnetic oxide ofnbsp;iron.� In addition to these bedded forms, there are alsonbsp;true veins in which graphite occurs associated with cal-cite, quartz, orthoclase, or pyroxene, and either in disseminated scales, in detached masses, or in bands or layersnbsp;� separated from each other and from the wall-rock bynbsp;feldspar, pyroxene, and quartz.� Dr. Hunt also mentions the occurrence of finely granular varieties, and ofnbsp;that peculiarly waved and corrugated variety simulatingnbsp;fossil wood, though really a mere form of laminatednbsp;structure, which also occurs at Warrensburg, Hew York,nbsp;and at the Marinski mine in Siberia. Many of the veinsnbsp;are not true fissures, but rather constitute a network ofnbsp;shrinkage cracks or segregation veins traversing in countless numbers the containing rock, and most irregular innbsp;their dimensions, so that they often resemble strings ofnbsp;nodular masses. It is most probable that the graphite ofnbsp;the veins was originally introduced as a liquid or plasticnbsp;hydrocarbon ; but in whatever way introduced, the character of the veins indicates that in the case of the greaternbsp;number of them the carbonaceous material must havenbsp;been derived from the bedded rocks traversed by thesenbsp;veins, to which it bears the same relation with the veins

of bitumen found in the bituminous shales of the Carboniferous and Silurian rocks. Nor can there be any doubt that the graphite found in the beds has been deposited along with the calcareous matter or muddy andnbsp;sandy sediment of which these beds were originally composed.¹

The quantity of graphite in the Lower Laurentian series is enormous. Some years ago, in the township ofnbsp;Buckingham, on the Ottawa Eiver, I examined a band ofnbsp;limestone believed to be a continuation of that describednbsp;by Sir �W�. E. Logan as the Green Lake limestone. Itnbsp;'quot;fas estimated to amount, with some thin interstratifiednbsp;bands of gneiss, to a thickness of six hundred feet ornbsp;�iore, and was found to be filled with disseminated crystals of graphite and veins of the mineral to such an extentnbsp;as to constitute in some places one-fourth of the whole ;nbsp;and, making every allowance for the poorer portions, thisnbsp;band cannot contain in all a less vertical thickness ofnbsp;pure graphite than from twenty to thirty feet. In thenbsp;adjoining township of Lochaber Sir W. E. Logan noticesnbsp;a band from twenty-five to thirty feet thick, reticulatednbsp;��'ith graphite veins to such an extent as to be mined withnbsp;profit for the mineral. At another place in the same district a bed of graphite from ten to twelve feet thick, andnbsp;yielding 20 per cent, of the pure material, is worked.

it appears in the excavation made by the quarrymen, it resembled a bed of coal; and a block from this bed,nbsp;about four feet thick, was a prominent object in thenbsp;Canadian department of the Colonial Exhibition of 1886.nbsp;When it is considered that graphite occurs in similarnbsp;abundance at several other horizons, in beds of limestonenbsp;which have been ascertained by Sir W. E. Logan to havenbsp;an aggregate thickness of thirty-five hundred feet, it is

Paper by the author on Laurentian Graphite, �Journal of London Geological Society � 18'76.

scarcely an exaggeration to maintain that the quantity of carbon in the Laurentian is equal to that in similar areasnbsp;of the Carboniferous system. It is also to be obseryednbsp;that an immense area in Canada appears to he occupiednbsp;by these graphitic and Eozoon limestones, and that richnbsp;graphitic deposits exist in the continuation of this system in the State of New York, while in rocks belieyed tonbsp;be of this age near St. John, New Brunswick, there is anbsp;yery thick bed of graphitic limestone, and associated withnbsp;it three regular beds of graphite, haying an aggregatenbsp;thickness of about fiye feet.¹

It may fairly he assumed that in the present world, and in those geological periods with whose organic remains we are more familiar than with those of the Laurentian, there is no other source of unoxidized carbon innbsp;rocks than that furnished by organic matter, and thatnbsp;this has obtained its carbon in all cases, in the first instance, from the deoxidation of carbonic acid by liyingnbsp;plants. No other source of carbon can, I belieye, benbsp;imagined in the Laurentian period. We may, howeyer,nbsp;suppose either that the graphitic matter of the Laurentiannbsp;has been accumulated in beds like those of coal, or thatnbsp;it has consisted of diffused bituminous matter similar tonbsp;that in more modern bituminous shales and bituminousnbsp;and oil-bearing limestones. The beds of graphite nearnbsp;St. John, some of those in the gneiss at Ticonderoga innbsp;New York, and at Lochaber and Buckingham, and elsewhere in Canada, are so pure and regular that one mightnbsp;fairly compare them with the graphitic coal of Ehodenbsp;Island. These instances, howeyer, are exceptional, andnbsp;the greater part of the disseminated and yein graphitenbsp;might rather be likened in its mode of occurrence to thenbsp;bituminous matter in bituminous shales and limestones.

Matthew in � Quarterly Journal of the Geological Society,� vol. xxi., p. 423.nbsp;nbsp;nbsp;nbsp;� Acadian Geology,� p. 662.

We may compare the disseminated graphite to that 'Which we find in those districts of Canada in which Silurian and Devonian bituminous shales and limestones havenbsp;teen metamorphosed and converted into graphitic rocksnbsp;not very dissimilar to those in the less altered portions ofnbsp;Ihe Laurentian.¹ In like manner it seems probable that

teen formed by the segregation of bituminous matter into fissures and planes of least resistance, in the manner innbsp;which such veins occur in modern bituminous limestonesnbsp;^nd shales. Such bituminous veins occur in the Lowernbsp;Carboniferous limestone and shale of Dorchester andnbsp;Hillsborough, New Brunswick, with an arrangement verynbsp;similar to that of the veins of graphite ; and in the Que-tec rocks of Point Levi, veins attaining to a thickness ofnbsp;�lore than a foot, are filled with a coaly matter having anbsp;transverse columnar structure, and regarded by Logannbsp;and Hunt as an altered bitumen. These palaeozoic analogies would lead us to infer that the larger part of thenbsp;Laurentian graphite falls under the second class of deposits above mentioned, and that, if of vegetable origin,nbsp;the organic matter must have been thoroughly disintegrated and bituminised before it was changed intonbsp;gmphite. This would also give a probability that thenbsp;i^ogetation implied was aquatic, or at least that it wasnbsp;nccumnlated under water.

Hr. Hunt has, however, observed an indication of terrestrial vegetation, or at least of subaerial decay, in the great beds of Laurentian iron-ore. These, if formed innbsp;tfie same manner as more modern deposits of this kind,nbsp;would imply the reducing and solvent action of substances produced in the decay of plants. In this casenbsp;such great ore-beds as that of Hull, on the Ottawa, seventy

Granby, Melbourne, Owl�s Head, amp;c., � Geology of Canada,� 1863, P- 699.

feet thick, or that near Newborough, two hundred feet thick,* must represent a corresponding quantity of irege-tahle matter which has totally disappeared. It may benbsp;added that similar demands on vegetable matter as anbsp;deoxidising agent are made by the beds and veins ofnbsp;metallic sulphides of the Laurentian, though some ofnbsp;the latter are no doubt of later date than the Laurentiannbsp;rocks themselves.

It would be very desirable to confirm such conclusions as those above deduced by the evidence of actual microscopic structure. It is to be observed, however, thatnbsp;when, in more modern sediments, Algse have been converted into bituminous matter, we cannot ordinarily obtain any structural evidence of the origin of such bitumen,nbsp;and in the graphitic slates and limestones derived fromnbsp;the metamorphosis of such rocks no organic structurenbsp;remains. It is true that, in certain bituminous shalesnbsp;and limestones of the Silurian system, shreds of organicnbsp;tissue can sometimes be detected, and in some cases, asnbsp;in the Lower Silurian limestone of the La Cloche Mountains in Canada, the pores of brachiopodous shells andnbsp;the cells of corals have been penetrated by black bituminous matter, forming what may be regarded as naturalnbsp;injections, sometimes of much beauty. In correspondencenbsp;with this, while in some Laurentian graphitic rocks, as,nbsp;for instance, in the compact graphite of Clarendon, thenbsp;carbon presents a curdled appearance due to segregation,nbsp;and precisely similar to that of the bitumen in morenbsp;modern bituminous rocks, I can detect in the graphiticnbsp;limestones occasional fibrous structures which may benbsp;remains of plants, and in some specimens vermicularnbsp;lines, which I believe to be tubes of Eozoon penetratednbsp;by matter once bituminous, but now in the state ofnbsp;graphite.

When palaeozoic land-plants have been converted into graphite, they sometimes perfectly retain their structure.nbsp;Mineral charcoal, with structure, exists in the graphiticnbsp;coal of Rhode Island. The fronds of ferns, with theirnbsp;minutest veins perfect, are preserved in the Devoniannbsp;shales of St. John, in the state of graphite; and in thenbsp;same formation there are trunks of Conifers {Dadoxylonnbsp;Ouangondianum^ in which the material of the cell-wallsnbsp;has been converted into graphite, while their cavitiesnbsp;have been filled with calcareous spar and quartz, thenbsp;finest structures being preserved quite as well as in comparatively unaltered specimens from the coal-formation.¹nbsp;Mo structures so perfect have as yet been detected in thenbsp;Laurentian, though in the largest of the three graphiticnbsp;beds at St. John there appear to be fibrous structures,nbsp;which I believe may indicate the existence of land-plants.nbsp;This graphite is composed of contorted and slickensidednbsp;laminm, much like those of some bituminous shales andnbsp;coarse coals; and in these are occasional small pyritousnbsp;masses which show hollow carbonaceous fibres, in somenbsp;cases presenting obscure indications of lateral pores. Inbsp;regard these indications, however, as uncertain; and it isnbsp;r¹ot as yet fully ascertained that these beds at St. Johnnbsp;are on the same geological horizon with the Lower Lau-rentian of Canada, though they certainly underlie thenbsp;Primordial series of the Acadian group, and are separated from it bv beds having the character of the Hu-

ronian.

There is thus no absolute impossibility that distinct crganic tissues may be found in the Laurentian graphite,nbsp;if formed from land-plants, more especially if any plantsnbsp;existed at that time having true woody or vascular tissues;nbsp;hut it cannot with certainty be affirmed that such tissues

� Acadian Geology,� p. 635. In calcified specimens the structures ��'^ttiain in the graphite alter deoalcification by an acid.

hare been found. It is possible, howeyer, that in the Laurentian period the vegetation of the land may havenbsp;consisted wholly of cellular plants, as, for example,nbsp;mosses and lichens; and if so, there would be comparatively little hope of the distinct preservation of theirnbsp;forms or tissues, or of our being able to distinguish thenbsp;remains of land-plants from those of Algae.

We may sum up these facts and considerations in the following statements: First, that somewhat obscurenbsp;traces of organic structure can be detected in the Laurentian graphite; secondly, that the general arrangementnbsp;and microscopic structure of the substance correspondsnbsp;with that of the carbonaceous and bituminous matters innbsp;marine formations of more modern date; thirdly, that ifnbsp;the Laurentian graphite has been derived from vegetablenbsp;matter, it has only undergone a metamorphosis similar innbsp;kind to that which organic matter in metamorphosednbsp;sediments of later age has experienced; fourthly, that thenbsp;association of the graphitic matter with organic limestone, beds of iron-ore, and metallic sulphides greatlynbsp;strengthens the probability of its vegetable origin; fifthly,nbsp;that when we consider the immense thickness and extentnbsp;of the Eozoonal and graphitic limestones and iron-orenbsp;deposits of the Laurentian, if we admit the organic originnbsp;of the limestone and graphite, we must be prepared tonbsp;believe that the life of that early period, though it maynbsp;have existed under low forms, was most copiously developed, and that it equalled, perhaps surpassed, in its results, in the way of geological accumulation, that of anynbsp;subsequent period.

Many years ago, at the meeting of the American Association in Albany, the writer was carrying into the room of the Geological Section a mass of fossil wood fromnbsp;the Devonian of Gasp�, when he met the late Professor.nbsp;Agassiz, and remarked that the specimen was the remains of a Devonian tree contemporaneous with his

fishes of that age. � How I wish I could sit under its shade ! � was the smiling reply of the great zoologist; andnbsp;when we think of the great accumulations of Laurentiannbsp;carbon, and that we are entirely ignorant of the formsnbsp;and structures of the vegetation which produced it, wenbsp;can scarcely suppress a feeling of disappointment. Somenbsp;things, however, we can safely infer from the facts thatnbsp;are known, and these it may be well to mention.

The climate and atmosphere of the Laurentian may have been well adapted for the sustenance of vegetablenbsp;life,nbsp;nbsp;nbsp;nbsp;scarcely doubt that the internal heat of the

earth still warmed the waters of the sea, and these warm Waters must have diffused great quantities of mists andnbsp;Vapours over the land, giving a moist and equable if not anbsp;Yery clear atmosphere. The vast quantities of cai�bon dioxide afterwards sealed up in limestones and carbonaceousnbsp;beds must also have still floated in the atmosphere andnbsp;�ust have supplied abundance of the carbon, which constitutes the largest ingredient in vegetable tissues. Tindernbsp;these circumstances the whole world must have resemblednbsp;^ damp, warm greenhouse, and plants loving such an atmosphere could have grown luxuriantly. In these circumstances the lower forms of aquatic vegetation andnbsp;those that love damp, warm air and wet soil would havmnbsp;ficcn at home.

_ It we ask more particularly what kinds of plants might be expected to be introduced in such circumstances,nbsp;We may obtain some information from the vegetation ofnbsp;the succeeding Palmozoic age, when such conditions stillnbsp;Continued to a modified extent. In this period the club-mosses, ferns, and mare�s-tails engrossed the world andnbsp;�'�6w to sizes and attained degrees of complexity of structure not known in modern times. In the previous Lau-mutian age something similar may have happened tonbsp;^Igae, to Fungi, to Lichens, to Liverworts, and Mosses.nbsp;The Algm may have attained to gigantic dimensions, and,

may have even ascended ont of the water in some of their forms. These comparatively simple cellular and tubularnbsp;structures, now degraded to the humble position of flatnbsp;lichens or soft or corky fungi, or slender cellular mosses,nbsp;may have been so strengthened and modified as to constitute forest-trees. This would be quite in harmony withnbsp;what is observed in the development of other plants innbsp;primitive geological times ; and a little later in this history we shall see that there is evidence in the flora of thenbsp;Silurian of a survival of such forms.

It may be that no geologist or botanist will ever te able to realise these dreams of the past. But, on thenbsp;other hand, it is quite possible that some fortunate chancenbsp;may have somewhere preserved specimens of Laurentiannbsp;plants showing their structure.

In any case we have here presented to us the strange and startling fact that the remarkable arrangement ofnbsp;protoplasmic matter and chlorophyll, which enables thenbsp;vegetable cell to perform, with the aid of solar light, thenbsp;miracle of decomposing carbon dioxide and water, andnbsp;forming with them woody and corky tissues, had alreadynbsp;been introduced upon the earth. It has been well saidnbsp;that no amount of study of inorganic nature would evernbsp;have enabled any one to anticipate the possibility of thenbsp;construction of an apparatus having the chemical powersnbsp;of the living vegetable cell. Yet this most marvellousnbsp;structure seems to have been introduced in the full plenitude of its powers in the Laurentian age.

Whether this early Laurentian vegetation was the means of sustaining any animal life other than marinenbsp;Protozoa, we do not know. It may have existed for itsnbsp;own sake alone, or merely as a purifier of the atmosphere,nbsp;in preparation for the future introduction of land-animals. The fact that there have existed, even in modernnbsp;times, oceanic islands rich in vegetation, yet untenantednbsp;by the higher forms of animal life, prepares us to believe

that such conditions may have heen general or universal in the primeval times we are here considering.

If we ask to what extent the carhon extracted from the atmosphere and stored up in the earth has heen,nbsp;or is likely to he, useful to man, the answer must henbsp;that it is not in a state to enable it to he used as mineral fuel. It has, however, important uses in the arts,nbsp;though at present the supply seems rather in excess ofnbsp;the demand, and it may well he that there are uses ofnbsp;graphite still undiscovered, and to which it will yet henbsp;applied.

Finally, it is deserving of notice that, if Laurentian graphite indicates vegetable life, it indicates this in vastnbsp;profusion. That incalculable quantities of vegetablenbsp;matter have been oxidised and have disappeared we maynbsp;helieve on the evidence of the vast beds of iron-ore ; and,nbsp;in regard to that preserved as graphite, it is certain thatnbsp;every inch of that mineral must indicate many feet ofnbsp;crude vegetable matter.

It is remarkable that, in ascending from the Laurentian, we do not at first appear to advance in evidences cf plant-life. The Huronian age, which succeeded thenbsp;Laurentian, seems to have been a disturbed and unquietnbsp;Lme, and, except in certain hands of iron-ore and somenbsp;dark slates coloured with carbonaceous matter, we find innbsp;it no evidence of vegetation. In the Cambrian a greatnbsp;suhsidenee of our continents began, which went on,nbsp;though with local intermissions and reversals, all throughnbsp;i'he Siluro-Camhrian or Ordovician time. These timesnbsp;^cre, for this reason, remarkable for the great abundancenbsp;and increase of marine animals rather than of land-plants,nbsp;^till, there are some traces of land vegetation, and we maynbsp;sketch first the facts of this kind which are known, andnbsp;then advert to some points relating to the earlier Algse,nbsp;or sea-Weeds.

scribed, under the name of Eophyfon, certain impressions on old Cambrian rocks in Sweden, and which certainlynbsp;present very plant-like forms. They want, howeyer, anynbsp;trace of carbonaceous matter, and seem rather to benbsp;grooves or marks cut in clay by the limbs or tails of somenbsp;aquatic animal, and afterwards filled up and preserved bynbsp;succeeding deposits. After examining large series ofnbsp;these specimens from Sweden, and from rocks of similarnbsp;age in Canada, I confess that I have no faith in theirnbsp;vegetable nature.

The oldest plants known to me, and likely to have been of higher grade than Algae, are specimens kindlynbsp;presented to me by Dr. Alleyne Nicholson, of Aberdeen,nbsp;and which he had named Buthotrephis Harhnessii¹ andnbsp;B. radiata. They are from the Skiddaw rocks of Cumberland. On examining these specimens, and othersnbsp;subsequently collected in the same locality by Dr. O. M.nbsp;Dawson, while convinced by their form and carbonaceousnbsp;character that they are really plants, I am inclined to refer them not to Algae, but probably to Rhizocarps. Theynbsp;consist of slender branching stems, with whorls of elongatenbsp;and pointed leaves, resembling the genus Annularia ofnbsp;the coal formation. I am inclined to believe that bothnbsp;of Nicholson�s species are parts of one plant, and fornbsp;this I have proposed the generic name Protannularianbsp;(Fig. 1). Somewhat higher in the Siluro-Cambrian, innbsp;the Cincinnati group of America, Lesquereux has foundnbsp;some minute radiated leaves, referred by him to the genusnbsp;Sphenophyllum,\ which is also allied to Rhizocarps. Stillnbsp;more remarkable is the discovery in the same beds of anbsp;stem with rhombic areoles or leaf-bases, to which thenbsp;name Protostigma has been given. J If a plant, this may

have been allied to the club-mosses. This seems to be all that we at present know of land-vegetation in thenbsp;Biluro-Cambrian. So far as the remains go, they indicatenbsp;the presence of thenbsp;families of Rhizo-carps and of Lyco-pods.

If we ascend into the Upper Silurian, or Silurian proper, the evidences of land vegetation somewhatnbsp;increase. In 1859 Inbsp;described, in � Thenbsp;Journal of the Geological Society,� ofnbsp;London, a remarkable tree from thenbsp;Lower Brian ofnbsp;Lasp�, under thenbsp;name Prototaxites,nbsp;hut for which Inbsp;now prefer thenbsp;name NematopJiy-ton. When in London, in 1870, I obtained permission to' examine certain specimens of spore-cases or seeds from the Uppernbsp;Ludlow (Silurian) formation of England, and whichnbsp;had been described by Sir Joseph Hooker under thenbsp;name Pachytheca. In the same' slabs with these Inbsp;found fragments of fossil wood identical with thosenbsp;of the Gasp� plant. Still later I recognised similarnbsp;fragments associated also with Pachytheca in the Silu-Lan of Cape Bon Ami, New Brunswick. Lastly, Dr.nbsp;Hicks has discovered similar wood, and also similar

From comparison of this singular wood, the structure of .which is represented in Figs. 2, 3, 4, with the debris

of fossil taxine woods, mineralised after long maceration in water, I was inclined to regard Prototaxites, or, as I

haye more recently named it, Nematophyton, as a primeval gymnosperm allied to those trees which Unger had described from the Brian of Thuringia, under the namenbsp;Aporoxylon¹ Later examples of more lax tissues fromnbsp;branches or young stems, and the elaborate examinationsnbsp;kindly undertaken for me by Professor Penhallow and

referred to in a note to this chapter, have induced me to modify this view, and to hold that the tissues of thesenbsp;singular trees, which seem to have existed from the be-

� Palaeontologie des Thuringcr Waldes,� 1856. t Figs. 2, 3, and 4 are drawn from nature by Prof. Penhallow, ofnbsp;McGill College.

ginning of the Silurian age and to hare finally disappeared in the early Erian, are altogether distinct from any form of yegetation hitherto known, and are possiblynbsp;surviyors of that prototypal fiora to which I haye alreadynbsp;referred. They are trees of large size, with a coaly barknbsp;and large spreading roots, haying the surface of the stemnbsp;smooth or irregularly ribbed, but with a nodose or jointednbsp;appearance. Internally, they show a tissue of long, cylindrical tubes, trayersed by a complex network of horizontalnbsp;tubes thinner walled and of smaller size. The tubes arenbsp;arranged in concentric zones, which, if annual rings, wouldnbsp;in some specimens indicate an age of one hundred andnbsp;fifty years. There are also radiating spaces, which I wasnbsp;at first disposed to regard as true medullary rays, or whichnbsp;at least indicate a radiating arrangement of the tissue.nbsp;They now seem to be spaces extending from the centrenbsp;towards the circumference of the stem, and to haye contained bundles of tubes gathered from the general tissuenbsp;and extending outward perhaps to organs or appendagesnbsp;on the surface. Carruthers has suggested a resemblancenbsp;to Algse, and has eyen proposed to change the name tonbsp;Nematophycus, or �thread-sea-weed�; but the resemblance is by no means clear, and it would be quite as reasonable to compare the tissue to that of some Fungi or Lichens, or eyen to suppose that a plant composed of cylindrical tubes has been penetrated by the mycelium or spawnnbsp;of a dry-rot fungus. But the tissues are too constant andnbsp;too manifestly connected with each other to justify thisnbsp;last supposition. That the plant grew on land I cannotnbsp;doubt, from its mode of occurrence; that it was of durable and resisting character is shown by its state of preser-yation; and the structure of the seeds called Pachytheca,nbsp;with their constant association with these trees, giye countenance to the belief that they are the fruit of Nema-tophyton. Of the foliage or fronds of these strangenbsp;plants we unfortunately know nothing. They seem, how-

ever, to realise the idea of arboreal plants having structures akin to those of thallophytes, but with seeds so large and complex that they can scarcely he regarded asnbsp;mere spores. They should perhaps constitute a separatenbsp;class or order to which the name Nematodendrece maynbsp;be given, and of which Nematophyton will constitute ouenbsp;genus and Aporoxylon of Unger another.¹

Another question arises as to the possible relation of these plants to other trees known by their external forms.nbsp;The Protostigma of Lesquereux has already been referrednbsp;to, and Claypole has described a tree from the Clintonnbsp;group of the United States, with large ovate leaf-bases, tonbsp;which he has given the name Olyptodendron.\ If thenbsp;markings on these plants are really leaf-bases, they cannbsp;scarcely have been connected with Nematophyton, becausenbsp;that tree shows no such surface-markings, though, as wenbsp;have seen, it had bundles of tubes passing diagonally tonbsp;the surface. These plants were more probably trees withnbsp;un axis of barred vessels and thick, cellular bark, like thenbsp;Lepidodendron of later periods, to be noticed in the sequel.nbsp;I3r. Hicks has also described from the same series of bedsnbsp;which afforded the fragments of Nematophyton certainnbsp;carbonised dichotomous stems, which he has named Ber-�^ynia. It is just possible that these plants may havenbsp;belonged to the Nematodendrese. The thick and densenbsp;coaly matter which they show resembles the bark of thesenbsp;trees, the longitudinal striation in some of them maynbsp;represent the fibrous structure, and the lateral projectionsnbsp;which have been compared to leaves or leaf-bases maynbsp;Correspond with the superficial eminences of Nematophyton, and the spirally arranged punctures which it showsnbsp;cu its surface. In this case I should be disposed to re-

See report by the author on � Brian Flora of Canada,� 1871 and 1882, for full description of these fossils,nbsp;t � American Journal of Science,� 1878.

gard the supposed stigmaria-like roots as really stems, and the supposed rootlets as short, spine-like rudimentary leaves. All such comparisons must, however, in thenbsp;mean time be regarded as conjectural. We seem, however, to have here a type of tree very dissimilar to anynbsp;even of the later Palaeozoic age, which existed throughout the Silurian, and probably further back, which ceasednbsp;to exist early in the Brian age, and before the appearancenbsp;of the ordinary coniferous and lepidodendroid trees.nbsp;May it not have been a survivor of an old arboreal floranbsp;extending back even to the Laurentian itself ?

Multitudes of markings occurring on the surfaces of the older rocks have been referred to the Algae or seaweeds, and indeed this group has been a sort of refuge fornbsp;the destitute to which palaeontologists have been accustomed to refer any anomalous or inexplicable form which,nbsp;while probably organic, could not be definitely referred tonbsp;the animal kingdom. There can be no question that somenbsp;of these are truly marine plants; and that plants of thisnbsp;kind occur in formations older than those in which we firstnbsp;find land-plants, and that they have continued to inhabitnbsp;the sea down to the present time. It is also true that thenbsp;oldest of these Algse closely resemble in form plants ofnbsp;this kind still existing ; and, since their simple cellularnbsp;structures and soft tissues are scarcely ever preserved,nbsp;their general forms are all that we can know, so that theirnbsp;exact resemblance to or difference from modern types cannbsp;rarely be determined. For the same reasons it has provednbsp;difficult clearly to distinguish them from mere inorganicnbsp;markings or the traces of animals, and the greatest divergence of opinion has occurred in recent times on-thesenbsp;subjects, as any one can readily understand who consultsnbsp;the voluminous and well-illustrated memoirs of Nathorst,nbsp;Williamson, Saporta, and Delgado.

The author of this work has given much attention to these remains, and has not been disposed to claim for the

YegetaWe kingdom so many of them as some of his contemporaries.¹ The considerations which seem most important in making such distinctions are the following ; !� The presence or absence of carbonaceous matter.nbsp;True A]g�e not infrequently present at least a thin film ofnbsp;carbon representing their organic matter, and this is thenbsp;Wore likely to occur in their case, as organic mattersnbsp;buried in marine deposits and not exposed to atmosphericnbsp;oxidation are very likely to be preserved. 3. In thenbsp;absence of organic matter, the staining of the containingnbsp;rock, the disappearance or deoxidation of its ferruginousnbsp;colouring matter, or the presence of iron pyrite may indicate the removal of organic matter by decay. 3. Whennbsp;organic matter and indications of it are altogether absent,nbsp;and form alone remains, we have to distinguish from Algae,nbsp;trails and burrows similar to those of aquatic animals,nbsp;casts of shrinkage-cracks, water-marks, and rill-marksnbsp;Y'idely diffused over the surfaces of beds. 4. Markingsnbsp;*iepressed on the upper surfaces of beds, and filled withnbsp;the material of the succeeding layer, are usually mere impressions. The cases of possible exceptions to this arenbsp;�^cry rare. On the contrary, there are not infrequentlynbsp;forms in relief on the surfaces of rocks which are notnbsp;-^IgEe, but may be shallow burrows arched upward on top,nbsp;�r castings of worms thrown up upon the surface. Some-fjrnes, however, they may have been left by denudationnbsp;of the surrounding material, just as footprints on drynbsp;snow remain in relief after the surrounding loose materialnbsp;bas been drifted away by the wind; the portion consolidated by pressure being better able to resist the denudingnbsp;Agency.

The footprints from the Potsdam sandstone in Canada, for which the name Protichnites was proposed by

� Impressions and Footprints of Aquatic Animals,� Journal of Science,� 1873.

Owen, and which were by him referred to crustaceans probably resembling Limulus, were shown by the writer,

in 1862,* to correspond precisely with those of thenbsp;American Limulus {Polyphemus Occidentalis) (Fig.nbsp;5). I proved by experiment with the modern animal that the recnrring series of groups of markingsnbsp;were produced by the toesnbsp;of the large posterior thoracic feet, the irregularnbsp;scratches seen in Protich-nites lineatus by the ordinary feet, and the central furrow by the tail. It was alsonbsp;shown that when the Limulus uses its swimming-feet itnbsp;produces impressions of the character of those named

Glimactichnites, from the same beds which afford Pro-tichnites. The principal difference between ProticJinites and their modern representatives is that the latter havenbsp;two lateral furrowsnbsp;produced by thenbsp;sides of the carapace, which arenbsp;�Wanting in the former.

I snbsequently applied the samenbsp;explanation to several other ancientnbsp;forms now knownnbsp;Rnder the general name Bilobitesnbsp;(Pigs. 6 and 7).¹

The tubercu-lated impressions known as Phyma-toderma and Gaul-^'f'pites may, as Zeil-ler has shown, benbsp;made by the burrowing of the mole-

erieket, and fine examples occurring in the Clinton formation of Canada are probably the work of Crustacea. It is probable, however, that some of the later forms referrednbsp;to these genera are really Algse related to Caulerpa, ornbsp;even branches of Conifers of the genns BracTiyphyllum.

Nereites and Planulites are tracks and burrows of ^orms, with or without marks of setae, and some of the

The name Bilobites was nriginally proposed by De Kay for a bivalve shell (Conocardium). Its application to supposed Algse was an error,nbsp;l�it this is of the less conseiiuenee, as these are not true plants but onlynbsp;animal trails.

markings referred to Palwochorda, PalcBophycus, and ScoUthus have their places here. Many examples highlynbsp;illustrative of the manner of formation of the impressionsnbsp;are afforded by Canadian rocks (Fig. 8).

Branching forms referred to Licrophycus of Billings, and some of those referred to Buthotrephis, Hall, as well

as radiating markings referable to Scotolithus,nbsp;Gyrophyllites, and As-terophycus, are explained by the branching burrows of wormsnbsp;illustrated by Nathorstnbsp;and the author. As-tropolithon, a singularnbsp;radiating marking ofnbsp;the Canadian Cambrian,¹ seems to be something organic, but ofnbsp;what nature is uncertain (Fig. 9).

Rhahdichnites and EopJiyton belong to impressions explicable bynbsp;the trails of driftingnbsp;sea-weeds, the tail-markings of Crustacea, and the rutsnbsp;ploughed by bivalve mollusks, and occurring in the Silurian, Brian, and Carboniferous rocks, f Among these arenbsp;the singular bilobate forms described as Busopliycus bynbsp;Hall, and which are probably burrows or resting-placesnbsp;of crustaceans. The tracks of such animals, when walking, are the Jointed impressions known as Arthrophycusnbsp;and Crusiana. I have shown by the mode of occurrence

of these, and Nathorst has confirmed this conclusion by elaborate experiments on living animals, that these formsnbsp;are really trails impressed on softnbsp;sediments by animals and mostlynbsp;by crustaceans.

I agree with Dr. Williamson ¹ in believing that all or nearly allnbsp;the forms referred to Crossochordanbsp;of Schim per are really animal impressions allied to Nereites, and duenbsp;either to worms or, as Nathorst hasnbsp;shown to be possible, to small crustaceans. Many impressions of thisnbsp;kind occur in the Silurian beds ofnbsp;the Clinton series in Canada andnbsp;New York, and are undoubtedlynbsp;Diere markings.

It is worthy of note that these Diarkings strikingly resemble the so-called Eophyton, described by Torellnbsp;from the Primordial of Sweden, andnbsp;by Billings from that of Newfoundland ; and which also occur abundantly in the Primordial of Newnbsp;Brunswick. After examining a series of these markings from Swedennbsp;shown to me by Mr. Carruthers innbsp;London, and also specimens from Newfoundland andnbsp;a large number in situ at St. John, I am convincednbsp;that they cannot be plants, but must be markings ofnbsp;the nature of RhaMiclinites. This conclusion is basednbsp;on the absence of carbonaceous matter, the intimatenbsp;nnion of the markings with the surface of the stone.

�Tracks from Yoredale Rocks,� �Manchester Literary and Philosophical Society,� 1885.

their indefinite forms, their want of nodes or appendages, and their markings being always of such a nature as could be produced by scratches of a sharp instrument. Since, however, fishes are yet unknown innbsp;beds of this age, they may possibly be referred to thenbsp;feet or spinous tails of swimming crustaceans. Salternbsp;has already suggested this origin for some scratches ofnbsp;somewhat different form found in the Primordial ofnbsp;Great Britain. He supposed them to have been thenbsp;work of species of Hymenocaris. These marks may,nbsp;however, indicate the existence of some free-swimming animals of the Primordial seas as yet unknownnbsp;to us.

Three other suggestions merit consideration in this connection. One is that Algse and also land-plants, drifting with tides or currents, often make the most remarkable and fantastic trails. A marking of this kind hasnbsp;been observed by Dr. G. M. Dawson to be produced bynbsp;a drifted Laminaria, and in complexity it resembled thenbsp;extraordinary JEnigmiclinus multiformis of Hitchcocknbsp;from the Connecticut sandstones. Much more simplenbsp;markings, of this kind would suffice to give species ofnbsp;Eophyton. Another is furnished by a fact stated to thenbsp;author by Prof. Morse, namely, that Lingulae, when dislodged from their burrows, trail themselves over thenbsp;bottom like worms, by means of their cirri. Colonies ofnbsp;these creatures, so abundant in the Primordial, may,nbsp;when obliged to remove, have covered the surfaces ofnbsp;beds of mud with vermicular markings. The third isnbsp;that the Rhabdichnite-markings resemble some of thenbsp;grooves in Silurian rocks which have been referred tonbsp;trails of Gasteropods, as, for instance, those from thenbsp;Clinton group, described by Hall.

Another kind of markings not even organic, but altogether depending on physical causes, are the beautiful branching rill-i^arks produced by the oozing of water

out of mud and sand-banks left by the tide, and which sometimes cover great surfaces with the most elaboratenbsp;tracery, on the modern tidal shores as well as in some ofnbsp;the most ancient rocks. Dendrophycus ¹ of Lesquereuxnbsp;seems to be an example of rill-mark, as well as Aristophy-cus, Glmphycus, and Zygophycus, of Miller and Dyer,nbsp;from the Lower Silurian.

Rill-marks occur in very old rocks, f but are perhaps most beautifully preserved in the Carboniferous shalesnbsp;and argillaceous sandstones, andnbsp;even more elaborately on the modern mud-banks of the Bay ofnbsp;Fundy.J Some of these simulatenbsp;ferns and fronds of Laminari�,nbsp;and others resemble roots, fucoidsnbsp;allied to ButhotrepMs, or the radiating worm-burrows already referred to (Pig. 10).

Shrinhage-cracks are also abundant in some of the Carboniferous teds, and are sometimes accompanied with impressions of raindrops. When finely reticulatednbsp;they might be mistaken for thenbsp;venation of leaves, and, whennbsp;complicated with little rill-marksnbsp;tributary to their sides, they precisely resemble the DictyoKtes ofnbsp;Hall from the Medina sandstone

An entirely different kind of shrinkage-crack is tnat vrhich occurs in certain carbonised and flattened plants,

� Coal Flora of Pennsylvania,� vol. lit, Plate 88. t �Journal of the Geological Society,� vol. xii., P- 251.nbsp;t �Acadian Geology,� 2d ed., p. 26.

and which sometimes communicates to them a marvellous resemblance to the netted under surface of an exogenousnbsp;leaf. Flattened stems of plants and layers of corticalnbsp;matter, when carbonised, shrink in such a manner as tonbsp;produce minute reticulated cracks. These become fillednbsp;with mineral matter before the coaly substance has beennbsp;completely consolidated. A further compression occurs,nbsp;causing the coaly substance to collapse, leaving the littlenbsp;veins of harder mineral matter projecting. These impress their form upon the clay or shale above and below,nbsp;and thus when the mass is broken open we have a car

with a network of raised lines, andnbsp;corresponding minute depressednbsp;lines on the shalenbsp;in contact with it.nbsp;The reticulationsnbsp;are generally irregular, but sometimes they verynbsp;closely resemblenbsp;the veins of a re-ticulately veinednbsp;leaf. One of thenbsp;most curious specimens in my possession was collected by Mr. Eldernbsp;in the Lower Carboniferous of Horton Bluff. The little veins which formnbsp;tha projecting network are in this case white calcite ; butnbsp;at the surface their projecting edges are blackened withnbsp;a carbonaceous film.

SlicJcensided todies, resembling the fossil fruits described by Geinitz as Qulielmites, and the objects believed

by Fleming and Carruthers ¹ to be casts of cavities filled with fluid, abound in the shales of the Carboniferous andnbsp;Devonian. They are, no doubt, in most cases the resultsnbsp;of the pressure and consolidation of the clay around smallnbsp;solid bodies, whether organic, fragmentary, or concretionary. They are, in short, local slickensides preciselynbsp;similar to those found so plentifully in the coal underclays, and which, as I have elsewhere f shown, resultednbsp;from the internal giving way and slipping of the mass asnbsp;the roots of Stigmaria decayed within it. Most collectorsnbsp;of fossil plants in the older formations must, I presume,nbsp;be familiar with appearances of this kind in connectionnbsp;with small stems, petioles, fragments of wood, and car-polites. I have in my collection petioles of ferns andnbsp;fruits of the genus Trigonocarpum partially sliokensidednbsp;in this way, and which if wholly covered by this kind ofnbsp;marking could scarcely have been recognised. I havenbsp;figured bodies of this kind in my report on the Devoniannbsp;und Upper Silurian plants of Canada, believing them,nbsp;owing to their carbonaceous covering, to be probablynbsp;slickensided fruits, though of uncertain nature. In everynbsp;case I think these bodies must have had a solid nucleus ofnbsp;some sort, as the severe pressure implied in slickensidingnbsp;is quite incompatible with a mere �fluid-cavity,� evennbsp;supposing this to have existed.

Prof. Marsh has well explained another phase of the influence of hard bodies in producing partial slickensides,nbsp;in his paper on Stylolites, read before the American Association in 1867, and the application of the combinednbsp;forces of concretionary action and slickensiding to thenbsp;production of the cone-in-cone concretions, which occurnbsp;m the coal-formation and as low as the Primordial. Inbsp;have figured a very perfect and beautiful form of this

kind from the coal-formation of l^ova Scotia, which is described in �Acadian Geology� ¹ (Fig. 12).

I have referred to these facts here because they are relatively more important in that older period, which maynbsp;he named the age of Algse, and because their settlementnbsp;now will enable us to dispense with discussions of thisnbsp;kind further on. The able memoirs of Nathorst andnbsp;Williamson should be studied by those who desire furthernbsp;information.

But it may be asked, � Are there no real examples of fossil Algae ? � I believe there are many such, but the dilH-

culty is to distinguish them. Confining ourselves to the oldernbsp;rocks, the followingnbsp;may be noted ;

The genus Bu-thotrepJm of Hall, w'hich is characterisednbsp;as having stems, sub-cylindric or compressed, with numerous branches, whichnbsp;are divaricating andnbsp;sometimes leaf-like,nbsp;contains some true Algae. Hall�s B. gracilis, from thenbsp;Siluro-Cambrian, is one of these. Similar plants, referrednbsp;to the same species, occur in the, Clinton and Niagaranbsp;formations, and a beautiful species, collected by Col.nbsp;Grant, of Hamilton, and now in the McGill College collection, represents a broader and more frondose type ofnbsp;distinctly carbonaceous character. It may be describednbsp;as follows :

fronds smootli and slightly striate longitudinally, wit curved and interrupted striae. Stem thick, bifurcating,nbsp;the divisions terminating in irregularly pinnate fron s,nbsp;apparently truncate at the extremities. khe quantity of carbonaceous matter present would i ndicatenbsp;thick, though perhaps flattened,nbsp;stems and densenbsp;fleshy fronds.

The species ButhotrepMs sub-nodosa and B.nbsp;flexuosa, fromnbsp;the Utica shale,nbsp;are also certainly plants, thoughnbsp;it is possible, ifnbsp;their strueturesnbsp;and fruit werenbsp;known, some ofnbsp;these might henbsp;referred to different genera. Allnbsp;of these plantsnbsp;have either carbonaceous matternbsp;or produce organic stains on thenbsp;niatrix.

Te^dge-shaped TrLds, described by Hall as Sphmothallu^^ angustifoUus, is also a plant. Ume specimens,nbsp;collection of the Geological Survey of Canada, show dis

tinct eyidence of the organic character of the wedge-shaped fronds. It is from the Utica shale, and elsewhere in the Siluro-Cambrian. It is just possible, as suggestednbsp;by Hall, that this plant may be of higher rank than thenbsp;Algje.

The genus Palceophycus of Hall includes a great variety of uncertain objects, of which only a few are probably true Algae. I have specimens of fragments similar to his P. virgatus, which show distinct carbonaceousnbsp;films, and others from the Quebec group, which seem tonbsp;be cylindrical tubes now flattened, and which have contained spindle-shaped sporangia of large size. Tortuousnbsp;and curved flattened stems, or fronds, from the Uppernbsp;Silurian limestone of Gasp�, also show organic matter.

Kespccting the forms referred to LicropJiycus by Billings, containing stems or semi-cylindrical markingsnbsp;springing from a common base, I have been in greatnbsp;doubt. I have not seen any specimens containing unequivocal organic matter, and am inclined to think thatnbsp;most of them, if not the whole, are casts of worm-burrows, with trails radiating from them.

Though I have confined myself in this notice to plants, or supposed plants, of the Lower Palaeozoic, it may benbsp;well to mention the remarkable Cauda-Galli fucoids, referred by Hall to the genus Spirophyton, and which arenbsp;characteristic of the oldest Brian beds. The specimensnbsp;which I have seen from Hew York, from Gasp�, andnbsp;from Brazil, leave no doubt in my mind that these werenbsp;really marine plants, and that the form of a spiral frond,nbsp;assigned to them by Hall, is perfectly correct. Theynbsp;must have been very abundant and very graceful plantsnbsp;of the early Brian, immediately after the close of thenbsp;Silurian period.

We come now to notice certain organisms referred to Algse, and which are either of animal origin, or are ofnbsp;higher grade than the sea-weeds. We have already dis-

cussed the questions relating to Prototaxites. Drepano-pTiycus, of Goeppert,¹ ² I suspect, is only a badly preserved branch or stem of the Erian land-plant known as Artliro-stigma. In like manner, Haliserites Dechenianus,\ ofnbsp;Goeppert, is evidently the land-plant known as Psilophy-ton. Sphmrococcites dentatus and 8. serra�the Fucoidesnbsp;dentatus and serra of Brongniart, from Quebec�arenbsp;graptolites of two species quite common there.J Dic-tyopliyton and Uphantenia, as described by Hall and thenbsp;author, are now known to be sponges. They have become DictyospongicB. The curious and very ancient fossils referred by Eorbes to the genus Oldhamia are perhapsnbsp;still subject to doubt, but are usually regarded as Zoophytes, though it is quite possible they may be plants.nbsp;Though I have not seen the specimens, I have no doubtnbsp;whatever that the plants, or the greater part of them,nbsp;from the Silurian of Bohemia, described by Stur as Algaenbsp;and Characeae,² are really land-plants, some of them ofnbsp;the genus Psilophyton. I may say in this connectionnbsp;that specimens of flattened Psilophyton and Arthrostig-'gt;na, in the Upper Silurian and Erian of Gasp�, wouldnbsp;probably have been referred to Algae, but for the fact thatnbsp;itt some of them the axis of barred vessels is preserved.

It is not surprising that great difficulties have occurred in the determination of fossil Algae. Enough, however,nbsp;remains certain to prove that the old Cambrian and Silurian seas were tenanted with sea-weeds not very dissimilarnbsp;from those of the present time. It is further probablenbsp;tiiat some of the graphitic, carbonaceous, and bituminous

nbsp;nbsp;nbsp;� Proceedings of the Vienna Academy,� 1881. Hostinella, of thisnbsp;author, is almost certainly Psilophyton, and his Barrandiana seems to include Arlhrostigma, and perhaps leafy branches of Berwynia. Thesenbsp;curious plants should be re-examined.

shales and limestones of the Silurian owe their carbonaceous matters to the decomposition of Algse, though possibly some of it may have been derived from Graptolites and other corneous Zoophytes. In any case, such micro

scopic examinations of these shales as I have made, have not produced any evidence of the existence of plants ofnbsp;higher grade, while those of the Erian and Carboniferousnbsp;periods, similar to the naked eye, abound in such evidence, It is also to be observed that, on the surfaces of

beds of sandstone in the Tipper Cambrian, carbonaceous dtbris, which seems to be the remains of either aquaticnbsp;or land plants, is locally not infrequent.

Referring to the land vegetation of the older rocks, it is difficult to picture its nature and appearance. Wenbsp;may imagine the shallow waters filled with aquatic or amphibious Rhizocarpean plants, vast meadows or brakes ofnbsp;the delicate Psilopliyton and the starry Protannularianbsp;and some tall trees, perhaps looking like gigantic club-mosses, or possibly with broad, flabby leaves, mostly cellular in texture, and resembling Algas transferred to the air.nbsp;Imagination can, however, scarcely realise this strangenbsp;and grotesque vegetation, which, though possibly copiousnbsp;and luxuriant, must have been simple and monotonous innbsp;aspect, and, though it must have produced spores andnbsp;seeds and even fruits, these were probably all of the typesnbsp;seen in the modern acrogens and gymnosperms.

Prophetic they truly were, as we shall find, of the more varied forests of succeeding times, and they maynbsp;also help us to realise the aspect of that still older vegetation, which is fossilised in the Laurentian graphite;nbsp;though it is not impossible that this last may have been ofnbsp;higher and more varied types, and that the Cambrian andnbsp;Silurian may have been times of depression in the vegetable world, as they certainly were in the submergence ofnbsp;much of the land.

These primeval woods served at least to clothe the Dakedness of the new-born land, and they may have sheltered and nourished forms of land-life still unknown to

as we find as yet only a few insects and scorpions in the Silurian. They possibly also served to abstract fromnbsp;the atmosphere some portion of its superabundant carbonic acid harmful to animal life, and they stored up

supplies of graphite, of petroleum, and of illuminating gas, useful to man at the present day. We may writenbsp;of them and draw their forms with the carbon whichnbsp;they themselves supplied.

Examination op Prototaxites {Nematophyton), by Prof. Pen-hallow, OF McGill University.

Prof. Penhallow, having kindly consented to re-examine my specimens, has furnished me witli elaborate notes of his facts andnbsp;conclusions, of which the following is a summary, but which it isnbsp;hoped will be published in full:

� 1. Concentric Layers.�The inner face of each of these is composed of relatively large tubes, having diameters from 13'6 to 34'6 micro-millimetres. The outer face has tubes ranging from 13'8 tonbsp;37'6 mm. The average diameter in the lower surface approaches to 34,nbsp;that in the outer to 18-8. There is, however, no abrupt terminationnbsp;to the surface of the layers, though in some specimens they separatenbsp;easily, with shining surfaces.

�3. Minute Structure.�In longitudinal sections the principal part of the structure consists of longitudinal tubes of indeterminatenbsp;length, and round in cross-section. They are approximately parallel,nbsp;but in some cases may be seen to bend sinuously, and are not innbsp;direct contact. Finer myceloid tubes, 5'33 mm. in diameter, traverse the structure in all directions, and are believed to branch ofEnbsp;from the larger tubes. In a small specimen supposed to be a branchnbsp;or small stem, and in which the vertical tubes are somewhat distantnbsp;from one another, this horizontal system is very largely developed;nbsp;but is less manifest in the older stems. The tubes themselves shownbsp;no structure. The ray-like openings in the substance of the tissuenbsp;are evidently original parts of the structure, but not of the nature ofnbsp;medullary rays. They are radiating spaces running outward in annbsp;interrupted manner or so tortuously that they appear to be interrupted in their course from the centre towards the surface. Theynbsp;show tubes turning into them, branching into them, and approximately horizontal, but tortuous. On the external surface of somenbsp;specimens these radial spaces are represented by minute pits irregu-

larly or spirally arranged. The transverse swellings of the stem show no difference of structure, except that the tubes or cells may benbsp;a little more tortuous, and a transverse film of coaly matter extendsnbsp;from the outer coaly envelope inwardly. This may perhaps benbsp;caused by some accident of preservation. The outer coaly layernbsp;shows tubes similar to those of the stem.¹ The horizontal or obliquenbsp;flexures of the large tubes seem to be mainly in the vicinity of thenbsp;radial openings, and it is in entering these that they have been seennbsp;to branch.�

� 1. The plant was not truly exogenous, and the appearance of rings is independent of the causes which determine the layers ofnbsp;growth in exogenous plants.

� 3. The plant was possessed of no true bark. Whatever cortical layer was present was in all probability a modification of the generalnbsp;structure, f

� 3. An intimate relation exists between the large tubular cells and the myceloid filaments, the latter being a system of smallnbsp;branches from the former; the branching being determined chiefly innbsp;certain special openings which simulate medullary rays.

� 4. The specimens examined exhibit no evidence of special decay, and the structure throughout is of a normal character.

� 5. The primary structure consists of large tubular cells without apparent terminations, and devoid of structural markings, withnbsp;which is associated a secondary structure of myceloid filaments arising from the former.

� 6. The structure of Nematophyton as a whole is unique; at least there is no plant of modern type with which it is comparable.nbsp;Nevertheless, the loose character of the entire structure; the interminable cells; their interlacing; and, finally, their branching into anbsp;secondary series of smaller filaments, point with considerable force tonbsp;the true relationship of the stem as being with Algee or other Thallo-phytes rather than with Gymnosperms. A more recent examination

It is possible that these tubes may be merely part of the stem attached to the bark, which seems to me to indicate the same dense cellular structure seen in the bark of Lepidodendra, etc.

f On these points I would reserve the considerations ; 1. That there must have been some relation between the mode of growth of these greatnbsp;stems and their concentric rings ; and, 2. That the evidence of a bark isnbsp;as strong as in the case of any Palaeozoic tree in which the bark is, asnbsp;usual, carbonised.

of a laminated resinous substance found associated with the plant shows that it is wholly amorphous, and, as indicated by distinct linesnbsp;of flow, that it must have been in a plastic state at a former period.nbsp;The only evidence of structure was found in certain well-definednbsp;mycelia, which may have been derived from associated vegetablenbsp;matter upon which they were growing, and over which the plasticnbsp;matrix flowed.�

I have only to add to this description that when we consider that Nematophyton Logani was a large tree, sometimes attaining a diameter of more than two feet, and a stature of at least twenty beforenbsp;branching; that it had great roots, and gave off large branches; thatnbsp;it was an aerial plant, probably flourishing in the same swampy flatsnbsp;with Psilophyton, Arthrostigma, and LeptopMeum ; that the peculiarnbsp;bodies known as Paehyfheca were not unlikely its fruit�we havenbsp;evidence that there were, in the early Palsozoic period, plantsnbsp;scarcely dreamt of by modern botany. Only when the appendagesnbsp;of these plants are more fully known can we hope to understandnbsp;them. In the mean time, I may state that there were probably different species of these trees, indicated more particularly by the stems Inbsp;have described as Nematoxylon and Celluloxylon.* There were, Inbsp;think, some indications that the plants described by Carruthers asnbsp;Berwynia, may also be found to have been generioally the same.nbsp;The resinous matter mentioned by Prof. Penhallow is found in greatnbsp;abundance in the beds containing Nematophyton, and must, I think,nbsp;have been an exudation from its bark.

CHAPTER III.

THE EEIAH OR HEVOHIAH FORESTS�ORIGIN OE PETROLEUM�THE AGE OR ACROGBNS AND GYMN08PERMS.

In the last chapter we were occupied with the comparatively few and obscure remains of plants entombed in the oldest geological formations. We now ascend to anbsp;higher plane, that of the Erian or Devonian period, innbsp;which, for the first time, we find varied and widely distributed forests.

The growth of knowledge with respect to this flora has been somewhat rapid, and it may be interesting tonbsp;note its principal stages, as an encouragement to the hopenbsp;that we may yet learn something more satisfactory respecting the older floras we have just discussed.

In Goeppert�s memoir on the flora of the Silurian, Devonian, and Lower Carboniferous rocks, published innbsp;I860,¹ he enumerates twenty species as Silurian, but thesenbsp;are all admitted to be Algae, and several of them are remains which may be fairly claimed by the zoologists asnbsp;zoophytes, or trails of worms and mollusks. In the Lowernbsp;Devonian he knows but six species, five of which arenbsp;Algae, and the remaining one a Sigillaria, but this is ofnbsp;very doubtful nature. In the Middle Devonian he givesnbsp;but one species, a land-plant of the genus Lepidodendron.nbsp;In the Upper Devonian the number rises to fifty-seven,nbsp;of which all but seven are terrestrial plants, representing

Goeppert does not include in his enumeration the plants from the Devonian of Gasp�, described by thenbsp;author in 1859,¹ having seen only an abstract of thenbsp;paper at the time of writing his memoir, nor does henbsp;appear to have any knowledge of the plants of this agenbsp;described by Lesquereux in Eogers�s �Pennsylvania.�nbsp;These might have added ten or twelve species to his list,nbsp;some of them probably from the Lower Devonian. It isnbsp;further to be observed that a few additional species hadnbsp;also been recognised by Peach in the Old Eed Sandstonenbsp;of Scotland.

But from 1860 to the present time a rich harvest of specimens has been gathered from the Gasp� sandstones,nbsp;from the shales of southern New Brunswick, from thenbsp;sandstones of Perry in Maine, and from the wide-spreadnbsp;Brian areas of New York, Pennsylvania, and Ohio.nbsp;Nearly all these specimens have passed through mynbsp;hands, and I am now able to catalogue about a hundred species, representing more than thirty genera, andnbsp;including all the great types of vascular Cryptogams, thenbsp;Gymnosperms, and even one (still doubtful) Angiospernnnbsp;Many new forms have also been described from the Devonian of Scotland and of the Continent of Europe.

Before describing these plants in detail, we may refer to North America for illustration of the physical conditions of the time. In a physical point of view the northern hemisphere presented a great change in the Briannbsp;period. There were vast foldings of the crust of thenbsp;earth, and great emissions of volcanic rock on both sidesnbsp;of the Atlantic. In North America, while at one timenbsp;the whole interior area of the continent, as far north as

�Journal of the Geological Society of London,� also �Canadian Naturalist.�

the Great Lakes, was occupied by a vast inland sea, studded with coral islands, the long Appalachian ridge had begunnbsp;to assume, along with the old Laurentian land, somethingnbsp;of the form of our present continent, and on the marginsnbsp;of this Appalachian belt there were wide, swampy flats andnbsp;shallow-water areas, which, under the mild climate thatnbsp;seems to have characterised this period, were admirablynbsp;suited to nourish a luxuriant vegetation. Under thisnbsp;mild climate, also, it would seem that new forms of plantsnbsp;were first introduced in the far north, where the longnbsp;continuance of summer sunlight, along with great warm th,nbsp;seems to have aided in their introduction and early extension, and thence made their way to the southward, anbsp;process which, as Gray and others have shown, has alsonbsp;occurred in later geological times.

The America of this Brian age consisted during the greater part of the period of a more or less extensive beltnbsp;of land in the north with two long tongues descendingnbsp;from it, one along the Appalachian line in the east, thenbsp;other in the region west of the Kocky Mountains. Onnbsp;the seaward sides of these there were low lands coverednbsp;quot;With vegetation, while on the inland side the great interior sea, with its verdant and wooded islands, realised,nbsp;though probably with shallower water, the conditions ofnbsp;the modern archipelagoes of the Pacific.

Europe presented conditions somewhat similar, having ill the earlier and middle portions of the period great seanbsp;areas with insular patches of land, and later wide tractsnbsp;af shallow and in part enclosed water areas, swarmingnbsp;^ith fishes, and having an abundant vegetation on theirnbsp;shores. These were the conditions of the Eifel andnbsp;Devonshire limestones, and of the Old Red Sandstone ofnbsp;Scotland, and the Kiltorcan beds of Ireland. In Europenbsp;also, as in America, there were in the Brian age greatnbsp;ejections of igneous rock. On both sides of the Atlanticnbsp;there were somewhat varied and changing conditions of

]and and water, and a mild and equable climate, permitting the existence of a rich Tegetation in high northern latitudes. Of this latter fact a remarkable example isnbsp;afforded by the beds holding plants of this age in Spitz-bergen and Bear Island, in its vicinity. Here there seemnbsp;to he two series of plant-bearing strata, one with thenbsp;vegetation of the Tipper Erian, the other with that ofnbsp;the Lower Carboniferous, though both have been unitednbsp;by Heer under his so-called �Hrsa Stage,� in which henbsp;has grouped the characteristic plants of two distinctnbsp;periods. This has recently been fully established by thenbsp;researches of Hathorst, though the author had alreadynbsp;suggested it as the probable explanation of the strangenbsp;union of species in the Hrsa group of Heer.

In studying the vegetation of this remarkable period, we must take merely some of the more important formsnbsp;as examples, since it would be impossible to notice allnbsp;the species, and some of them may be better treated innbsp;the Carboniferous, where they have their headquarters.nbsp;(Fig. 15.)

I may first refer to a family which seems to have culminated in the Erian age, and ever since to have occupied a less important place. It is that of the curious aquaticnbsp;plants known as Ehizocarps,¹ and referred to in the lastnbsp;chapter.

My attention was first directed to these organisms by the late Sir W. E. Logan in 1869. He had obtained fromnbsp;the Upper Erian shale of Kettle Point, Lake Huron,nbsp;specimens filled with minute circular discs, to which henbsp;referred, in his report of 1863, as �microscopic orbicularnbsp;bodies.� Eecognising them to be macrospores, or spore-cases, I introduced them into the report on the Erian

Or, as they have recently been named by some botanists, � Hete-rosporous Filices,� though they are certainly not ferns in any ordinary

flora, which I was then preparing, and which was published in 1871, under the name Sporangites Huronensis.

In 1871, having occasion to write a communication to the �American Journal of Science� on the question then

raised as to the share of spores and spore-cases in the accumulation of coal, a question to be discussed in a sub-

sequent chapter, these curious little bodies were again reviewed, and were described in substance as follows :

� The oldest bed of spore-cases known to me is that at Kettle Point, Lake Huron. It is a bed of brownnbsp;bituminous shale, burning with much flame, and undernbsp;a lens is seen to be studded with flattened disc-like bodies,nbsp;scarcely more than a hundredth of an inch in diameter,nbsp;which under the microscope are found to be spore-casesnbsp;(or macrospores) slightly papillate externally (or morenbsp;properly marked with dark pores), and sometimes showing a point of attachment on one side and a slit more ornbsp;less elongated and gaping on the other. When slices ofnbsp;the rock are made, its substance is seen to be filled withnbsp;these bodies, which, viewed as transparent objects, appearnbsp;yellow like amber, and show little structure, except thatnbsp;the walls can be distinguished from the internal cavity,nbsp;which may sometimes be seen to enclose patches of granular matter. In the shale containing them are also vastnbsp;numbers of rounded, translucent granules, which may benbsp;escaped spores (microspores).� The bed containing thesenbsp;spores at Kettle Point was stated, in the reports of thenbsp;�Geological Survey of Canada,� to be twelve or fourteennbsp;feet in thickness, and besides these specimens it containednbsp;fossil plants referable to the species Calamites inornatusnbsp;and Lepidodendron primmvum, and I not unnaturallynbsp;supposed that the Sporangites might be the fruit of thenbsp;latter plant. I also noticed their resemblance to thenbsp;spore-cases of L. corrugatum of the Lower Carboniferousnbsp;(a Lepidodendron allied to L. primmvum), and to thosenbsp;from Brazil described by Carruthers under the namenbsp;Flemingites, as well as to those described by Huxleynbsp;from certain English coals, and to those of the Tasmanitenbsp;or white coal of Australia. The bed at Kettle Point isnbsp;shown to be marine by its holding the sea-weed knownnbsp;as Spirophyton, and shells of Lingula.

1882, when Prof. Orton, of Columbus, Ohio, sent me some specimens from the Brian shales of that State,nbsp;which on comparison seemed undistinguishahle fromnbsp;Sporangites Huronensis¹ Pro� Orton read an interesting paper on these bodies, at the meeting of the Americannbsp;Association in Montreal, in which were some new andnbsp;striking facts. One of these was the occurrence of suchnbsp;bodies throughout the black shales of Ohio, extendingnbsp;� from the Huron River, on the shore of Lake Brie, tonbsp;the mouth of the Scioto, in the Ohio Valley, with annbsp;extent varying from ten to twenty miles in breadth,� andnbsp;estimated to be three hundred and fifty feet in thickness.nbsp;I have since been informed by my friend Mr. Thomas, ofnbsp;Chicago, that its thickness, in some places at least, mustnbsp;be three times that amount. About the same time. Prof.nbsp;Williams, of Cornell, and Prof. Clarke, of Northampton,nbsp;announced similar discoveries in the State of New York,nbsp;so that it would appear that beds of vast area and of greatnbsp;thickness are replete with these little vegetable discs, usually converted into a highly bituminous, amber-like substance, giving a more or less inflammable character to thenbsp;containing rock.

Another fact insisted on by Prof. Orton was the absence of Lepidodendroid cones, and the occurrence of filamentous vegetable matter, to which the Sporangitesnbsp;seemed to be in some cases attached in groups. Prof.nbsp;Orton also noticed the absence of the trigonal form, whichnbsp;belongs to the spores of many Lepidodendra, though thisnbsp;is not a constant character. In the discussion on Prof.nbsp;Orton�s paper, I admitted that the facts detailed by himnbsp;shook my previous belief of the lycopodiaceous character

These shales have been described, as to their chemical and geological relations, by Dr. T. Sterry Hunt, �American Journal of Science,� 1863,nbsp;and by Dr. Newberry, in the �Reports of the Geological Survey of Ohio,�nbsp;vol. i., 1863, and vol. iii., 1878.

of these bodies, and induced me to suspect, with Prof. Orton, that they might hare belonged to some group ofnbsp;aquatic plants lower than the Lycopods.

Since the publication of my paper on Ehizocarps in the Palaeozoic period above referred to, I have receivednbsp;two papers from Mr. Edward Wethered, E. G. S., in onenbsp;of which he describes spores of plants found in the lowernbsp;limestone shales of the Forest of Dean, and in the othernbsp;discusses more generally the structure and origin of Carboniferous coal-beds.¹ In both papers he refers to thenbsp;occurrence in these coals and shales of organisms essentially similar to the Erian spores.

In the �Bulletin of the Chicago Academy of Scienee,� January, 1884, Dr. Johnson and Mr. Thomas, in theirnbsp;paper on the � Microscopic Organisms of the Boulder Claynbsp;of Chicago and Vicinity,� notice Sporangites Huronensisnbsp;as among these organisms, and have discovered them alsonbsp;in large numbers in the precipitate from Chicago citynbsp;water-supply. They refer them to the decomposition ofnbsp;the Erian shales, of which boulders filled with these organisms are of frequent occurrence in the Chicago clays.nbsp;The Sporangites and their accompaniments in the bouldernbsp;clay are noticed in a paper by Dr. G. M. Dawson, in thenbsp;� Bulletin of the Chicago Academy,� June, 1885.

Prof. Clarke has also described, in the �American Journal of Science� for April, 1885, the forms alreadynbsp;alluded to, and which he finds to consist of macrosporesnbsp;enclosed in sporocarps. He compares these with mynbsp;Sporangites Huronensis and Protosalvinia bilobata, butnbsp;I think it is likely that one of them at least is a distinctnbsp;species.

I may add that in the �Geological Magazine� for 1875, Mr. Newton, F. G. S., of the Geological Survey of

� Cotteswold Naturalists� Field Club,� 1884; � Journal of the Royal Microscopical Society,� 1886.

England, published a description of the Tasmanite and Australian white coal, in which he shows that the organisms in these deposits are similar to my Sporangitesnbsp;Huronensis, and to the macrospores previously describednbsp;by Prof. Huxley, from the Better-bed coal. Mr. Hewtonnbsp;does not seem to have been aware of my previous description of Sporangites, and proposes the name Tasmanitesnbsp;punctatus for the Australian form.

Here we have the remarkable fact that the waste macrospores, or larger spores of a species of Cryptoga-mous plant, occur dispersed in countless millions of tonsnbsp;through the shales of the Erian in Canada and the Unitednbsp;States.

No certain clue seemed to be afforded by all these observations as to the precise affinities of these widelynbsp;distributed bodies; but this was furnished shortly afternbsp;from an unexpected quarter. In March, 1883, Mr. Orville Derby, of the Geological Survey of Brazil, sent menbsp;specimens found in the Erian of that country, whichnbsp;seemed to throw a new light on the whole subject. Thesenbsp;I described and pointed out their connection with Sporangites at the meeting of the American Association at Minneapolis, in 1883, and subsequently published my notesnbsp;respecting them in its proceedings, and in the ^�Canadiannbsp;Record of Science.�

Mr. Derby�s specimens contained the curious spiral sea-weed known as SpiropJiyton, and also minute roundednbsp;Sporangites like those obtained in the Erian of Ohio, andnbsp;of which specimens had been sent to me some years before by the late Prof. Hartt. But they differed in showing the remarkable fact that these rounded bodies arenbsp;enclosed in considerable numbers in spherical and ovalnbsp;sacs, the walls of which are composed of a tissue ofnbsp;hexagonal cells, and which resemble in every respect thenbsp;involucres or spore-sacs of the little group of modernnbsp;acrogens known as Ehizocarps, and living in shallow

water. More especially they resemble the sporocarps of the germs Salvinia. This fact opened up an entirelynbsp;new field of investigation, and I at once proceeded tonbsp;compare the specimens with the fructification of modernnbsp;Ehizocarps, and found that substantially these multitudinous spores embedded in the Erie shales may be regarded as perfectly analogous to the larger spores of thenbsp;modern Salvinia natans of Europe, as may be seen bynbsp;the representation of them in Fig. 16.

The typical macrospores from the Erian shales are perfectly circular in outline, and in the flattened state appear as discs with rounded edges, their ordinary diameternbsp;being from one seventy-fifth to one one hundredth of annbsp;inch, though they vary considerably in size. This, however, I do not regard as an essential character. Thenbsp;edges, as seen in profile, are smooth, but the fiat surfacenbsp;often presents minute dark spots, which at first I mis-

took for papillffi, but now agree with Mr. Thomas in recognising them as minute pores traversing the wall of the disc, and similar to those which Mr. Newton has describednbsp;in Tasmanite, and which Mr. Wethered has also recognised in the similar spores of the Forest of Dean shales.nbsp;The walls also sometimes show faint indications of concentric lamination, as if they had been thickened by successive deposits.

As seen by transmitted light, and either in front or in profile, the discs are of a rich amber colour, translucentnbsp;and structureless, except the pores above referred to.nbsp;The walls are somewhat thick, or from one-tenth to one-twentieth the diameter of the disc in thickness. Theynbsp;never exhibit the triradiate marking seen in spores of Ly-copods, nor any definite point of attachment, thoughnbsp;they sometimes show a minute elongated spot which maynbsp;be of this nature, and they are occasionally seen to havenbsp;opened by slits on the edge or front, where there wouldnbsp;seem to have been a natural line of dehiscence. The interior is usually quite vacant or structureless, but in somenbsp;cases there are curved internal markings which may indicate a shrunken lining membrane, or the remains of anbsp;prothallus or embryo. Occasionally a fine granular substance appears in the interior, possibly remains of microspores.

The discs are usually detached and destitute of any envelope, but fragments of flocculent cellular matter arenbsp;associated with them, and in one specimen from the cor-niferous limestone of Ohio, in Mr. Thomas�s collection, Inbsp;have found a group of eight or more discs partly enclosednbsp;in a cellular sac-like membrane of similar character tonbsp;that enclosing the Brazilian specimens already referred to.

The characters of all the specimens are essentially similar, and there is a remarkable absence of other organisms in the shale. In one instance only, I have observednbsp;a somewhat smaller round body with a dark centre or

nucleus, and a wide translucent margin, marked by a slight granulation. Even this, however, may indicatenbsp;nothing more than a different state of preservation.

It is proper to observe here that the wall or enclosing sac of these macrospores must have been of very densenbsp;consistency, and now appears as a highly bituminous substance, in this agreeing with that of the spores of Lyco-pods, and, like them, having been when reoent of a highlynbsp;carbonaceous and hydrogenous quality, very combustiblenbsp;and readily admitting of change into bituminous matter.nbsp;In the paper already referred to, on spore-cases in coals,nbsp;I have noticed that the relative composition of lycopodium and cellulose is as follows :

Thus, such spores are admirably suited for the production of highly carbonaceous or bituminous coals, etc.

�sTothing is more remarkable in connection with these bodies than their uniformity of structure and form overnbsp;so great areas and throughout so great thickness of rock,nbsp;and the absence of any other kind of spore-case. Thisnbsp;is more especially noteworthy in contrast with the coarsenbsp;coals and bituminous shales of the Carboniferous, whichnbsp;usually contain a great variety of spores and sporangia,nbsp;indicating the presence of many species of acrogenousnbsp;plants, while the Erian shales, on the contrarj^, indicate thenbsp;almost exclusive predominance of one form. This contrast is well seen in the Bedford shales overlying thesenbsp;beds, and I believe Lower Carboniferous. ¹ Specimens ofnbsp;these have been kindly communicated to me by Prof.nbsp;Orton, and have been prepared by Mr. Thomas. In thesenbsp;we see the familiar Carboniferous s23ores with triradiatenbsp;markings called Triletes by Eeinsch, and which are similar to those of Lycopodiaceous plants. Still more abun-

dant are those spinous and hooked spores or sporangia, to which the names Sporocarpon, Zygosporites, and Tra-quaria have been given, and some of which Williamsonnbsp;has shown to he spores of Lycopodiaceons plants.¹

The true � Sporangites,� on the contrary, are round and smooth, with thick bituminous walls, which arenbsp;punctured with minute transverse pores. In these respects, as already stated, they closely resemble the bodiesnbsp;found in the Australian white coal and Tasmanite. Thenbsp;precise geological age of this last material is not knownnbsp;with certainty, but it is believed to be Palseozoic.

With reference to the mode of occurrence of these bodies, we may note first their great abundance and widenbsp;distributiom The horizontal range of the bed at Kettlenbsp;Point is not certainly known, but it is merely a northernnbsp;outlier of the great belt of Brian shales referred to bynbsp;Prof. Orton, and which extends, with a breadth of ten tonbsp;twenty miles, and of great thickness, across the State ofnbsp;Ohio, for nearly two hundred miles. This Ohio blacknbsp;shale, which lies at the top of the Brian or the base ofnbsp;the Carboniferous, though probably mainly of Brian age,nbsp;appears to abound throughout in these organisms, and innbsp;some beds to be replete with them. In like manner, innbsp;Brazil, according to Mr. Derby, these organisms are distributed over a wide area and throughout a great thickness of shale holding Spirophyton, and apparently belonging to the Upper Brian. The recurrence of similar formsnbsp;in the Tasmanite and white coal of Tasmania and Australia is another important fact of distribution. To this

Traquaria is to be 4jstinguisbed from tbe oaleareous bodies found in the corniferous limestone of Kelly�s Island, which I have described innbsp;the �Canadian Naturalistquot; as Saccamina Eriana, and believe to be Fo-raminiferal tests. They have since been described by IJlrich under anbsp;different name (Moellerina: contribution to � American Palaeontology,�nbsp;1886). See Dr. Williamson�s papers in �Transactions of Royal Societynbsp;of London.�

we may add the appearance of these macrospores in coals and shales of the Oarboniferons period, though there innbsp;association with other forms.

It is also to be observed that the Brian shales, and the Forest of Dean beds described by Wethered, are marine,nbsp;as shown by their contained fossils ; and, though I havenbsp;no certain information as to the Tasmanite and Australian white coal, they would seem, from the description ofnbsp;Milligan, to occur in distinctly aqueous, possibly estuarine, deposits. Wethered has shown that the discs described by Huxley and Hewton in the Better-bed coalnbsp;occur in the earthy or fragmentary layers, as distinguished from the pure coal. Those occurring in cannelnbsp;coal are in the same case, so that the general mode ofnbsp;occurrence implies water-driftage, since, in the case ofnbsp;bodies so large and dense, wind-driftage to great distancesnbsp;would be impossible.

These facts, taken in connection with the differences between these macrospores and those of any known land-plant of the Palaeozoic, would lead to the inference thatnbsp;they belonged to aquatic plants, and these vastly abundantnbsp;in the waters of the Brian and Carboniferous periods.

It is still further to be observed that they are not, in the Brian beds, accompanied with any remains of woodynbsp;or scalariform tissues, such as might be expected in connection with the debris of terrestrial acrogens, and that,nbsp;on the other hand, we find them enclosed in cellularnbsp;sporocarps, though in the majority of cases these havenbsp;been removed by dehiscence or decay.

These considerations, I think, all point to the probability which I have suggested in my papers on this subject referred to above, that we have in these objects the organs of fructification of plants belonging to the ordernbsp;Rhizocarpem, or akin to it. The comparisons which Inbsp;have instituted with the sporocarps and macrospores ofnbsp;these plants confirm this suggestion. Of the modern

species �which I have had an opportunity to examine, Salvinia natans of Europe perhaps presents the closestnbsp;resemblance. In this plant groups of round cellularnbsp;sporocarps appear at the bases of the floating fronds.nbsp;They are about a line in diameter when mature, and arenbsp;of two kinds, one containing macrospores, the other microspores or antheridia. The first, when mature, hold anbsp;number of closely packed globular or oval sporangia ofnbsp;loose cellular tissue, attached to a central placenta. Eachnbsp;of these sporangia contains a single macrospore, perfectlynbsp;globular and smooth, with a dense outer membrane (exhibiting traces of lamination, and showing within annbsp;irregularly vacuolated or cellular structure, probably anbsp;prothallus). I cannot detect in it the peculiar poresnbsp;which appear in the fossil specimens. Each macrosporenbsp;is about one-seventieth of an inch in diameter when mature. The sporocarps of the microspores contain a vastlynbsp;greater number of minute sporangia, about one two-hundredths of an inch in diameter. These contain disc-likenbsp;antheridia, or microspores of very minute size.

The discs from Kettle Point and from the Ohio black shale, and from the shale boulders of the Chicago clays,nbsp;are similar to the macrospores of Salvinia, except thatnbsp;they have a thicker wall and are a little less in diameter,nbsp;being about one-eightieth of an inch. The Braziliannbsp;sporocarps are considerably larger than those of the modern Salvinia, and the macrospores approach in size tonbsp;those of the modern species, being one seventy-fifth of annbsp;inch in diameter. They also seem, like the modern species, to have thinner walls than those from Canada, Ohio,nbsp;and Chicago. Ko distinct indication has been observednbsp;in the fossil species of the inner Sporangium of Salvinia.nbsp;Possibly it was altogether absent, but more probably it isnbsp;not preserved as a distinct structure.

With reference to the microspores of Salvinia, it is to be observed that the sporocarps, and the contained spores

or antheridia, are Tery delicate and destitute of the dense outer wall of the macrospores. Hence such parts arenbsp;little likely to have heen preserved in a fossil state ; andnbsp;in the Brian shales, if present, they probably appearnbsp;merely as flocculent carbonaceous matter not distinctlynbsp;marked, or as minute granules not well defined, of whichnbsp;there are great quantities in some of the shales.

The vegetation appertaining to the Sporangites has not been distinctly recognised. I have, however, foundnbsp;in one of the Brazilian specimens two sporocarps attachednbsp;to what seems a fragment of a cellular frond, and numerous specimens of the supposed Algae, named Spiropliyton,nbsp;are found in the shales, hut there is no evidence of anynbsp;connection of this plant with the Protosalvinia.

Modern Khizocarps present considerable differences as to their vegetative parts. Some, like Pilularia, havenbsp;simple linear leaves ; others, like Marsilea, have leaves innbsp;whorls, and cuneate in form; while others, like Azollanbsp;and Salvinia, have frondose leaves, more or less pinnatenbsp;in their arrangement. If we inquire as to fossils representing these forms of vegetation, we shall find that somenbsp;of the plants to be noticed in the immediate sequel maynbsp;have been nearly allied to the Ehizoearps. In the meannbsp;time I may state that I have proposed the generic namenbsp;Protosalvinia for these curious macrospores and theirnbsp;coverings, and have described in the paper in the � Bulletin of the Chicago Academy of Sciences,� alreadynbsp;quoted, five species which may be referred to this genus.

These facts lead to inquiries as to the origin of the bituminous matter which naturally escapes from thenbsp;rocks of the earth as petroleum and inflammable gas, ornbsp;which may be obtained from certain shales in these formsnbsp;by distillation. These products are compounds of carbonnbsp;and hydrogen, and ma}^ be procured from recent vegetablenbsp;substances by destructive distillation. Some vegetablenbsp;matters, also, are much richer in carbon and hydrogen

than others, and it is a remarkable fact that the spores of certain cryptogamous plants are of this kind, as we see innbsp;the inflammable character of the dry spores of Lycopodium ; and we know that the slow putrefaction of suchnbsp;material underground effects chemical changes by whichnbsp;bituminous matter can be produced. There is, therefore, nothing unreasonable in the supposition advancednbsp;by Prof. Orton, that the spores so abundantly containednbsp;in the Ohio black shales are important or principal sourcesnbsp;of the bituminous matter which they contain. Microscopic sections of this shale show that much of its material consists of the rich bituminous matter of these sporesnbsp;(Fig. 16). At the same time, while we may trace thenbsp;bitumen of these shales, and of some beds of coal, to thisnbsp;cause, we must bear in mind that there are other kinds ofnbsp;bituminous rocks which show no such structures, and maynbsp;have derived their combustible material from other kindsnbsp;of vegetable matter, whether of marine or of land plants.nbsp;We shall better understand this when we have considerednbsp;the origin of coal.

The macrospores above referred to may have belonged to humble aquatic plants mantling the surfaces of waternbsp;or growing up from the bottom, and presenting littlenbsp;aerial vegetation. But there are other Brian plants, asnbsp;already mentioned, which, while of higher structure, maynbsp;be of Rhizocarpean affinities.

One of these is the beautiful plant with whorls of wedge-shaped leaves, to which the name Sphenopliyllumnbsp;(see Fig. 30) has been given. Plants referred to thisnbsp;genus have been described by Lesquereux from the uppernbsp;part of the Siluro-Cambrian,¹ and a beautiful little species occurs in the Brian shales of St. John, New Brunswick, f The genus is also continued, and is still more

� American Journal of Science.� t Dawson, � Report on Devonian Plants,� ISIO.

abuBdant, in the Carboniferous. Many years ago I observed, in a beautiful specimen collected by Sir W. E. Logan, in Ifew Brunswick, that the stem of this plantnbsp;had an axis of reticulated and sealariform vessels, and annbsp;outer bark.¹ Eenault and Williamson have more recentlynbsp;obtained more perfect specimens, and the former hasnbsp;figured a remarkably complex triangular axis, containingnbsp;punctate and barred vessels, and larger punctate vesselsnbsp;filling in its angles. Outside of this there is a cellularnbsp;inner bark, and this is surrounded by a thick fibrous envelope. That a structure so complex should belong tonbsp;a plant so humble in its affinities is one of the strangenbsp;anomalies presented by the old world, and of which wenbsp;shall find many similar instances. The fruit of 8pheno-pliyllum was borne in spikes, with little whorls of bractsnbsp;or rudimentary leaves bearing round sporocarps.

A second type of plant, which may have been Ehizo-carpean in its affinities, is that to which I have given the name Ptilophyton.\ It consists of beautiful feathery

fronds, apparently bearing on parts of the main stem or petiole small rounded sporocarps. They are found abundantly in the Middle Erian of the State of New York,nbsp;and also occur in Scotland, while one species appears tonbsp;occur in Nova Scotia, as high as the Lower Carboniferousnbsp;(Figs. 17, 18). _

These organisms have been variously referred to Lyco-pods, to Algse, or to Zoophytes, but an extended compari-

son of American and Scottish specimens has led me to the belief that they were aquatic plants, more likely tonbsp;have been allied to Ehizocarps than to any other group.nbsp;Some evidence of this will be given in a note appendednbsp;to this ehapter.

Another genus, which I have namednbsp;Psilophyton ¹ (Figs.nbsp;19, 21), may be regarded as a connecting link between thenbsp;Ehizoearps and thenbsp;Lycopods. It is sonbsp;named from its resemblance, in some respects, to the curious parasitic Lycopodsnbsp;placed in the modernnbsp;genus PsUotum. Several species have beennbsp;described, and they arenbsp;eminently characteristic of the Lower Eri-an, in which theynbsp;were first discoverednbsp;in Gasp�. The typical species, Psilophyton princeps, whichnbsp;fills many beds of shalenbsp;and sandstone in Gasp� Bay and the headnbsp;of the neighbouringnbsp;Bay des Chaleurs withnbsp;its slender stems andnbsp;creeping, cord-like rhizomes, may be thus described :

�Journal of the Geological Society,� vols. xv., xviii., and xix., �Report on Devonian Plants of Canada,� 1811.

dichotomously, and covered with interrupted ridges. Leaves rudimentary, or short, rigid, and pointed; innbsp;barren steins, numerous and spirally arranged ; in fertilenbsp;stems and branchlets, sparsely scattered or absent; innbsp;decorticated specimens, represented bynbsp;nbsp;nbsp;nbsp;a

minute punctate scars. Young branches circinate ; rhizomata cylindrical, covered with hairs or ramenta, and having circular areoles irregularly disposed, giving origin to slender cylindrical rootlets.

Internal structure�an axis of scalari-form vessels, surrounded by a cylinder of parenchymatous cells, and by an outernbsp;cylinder of elongated woody cells. Fructification consisting of naked oval spore-cases, borne usually in pairs on slender,nbsp;curved pedicels, either lateral or terminal.

This species was fully described by me in the papers referred to above, from specimens obtained from the richnbsp;exposures at Gasp� Bay, and which enabled me to illustrate its parts more fully, perhaps, than those of anynbsp;other species of so great antiquity. In the specimens Inbsp;had obtained I was able to recognise the forms of thenbsp;rhizomata, stems, branches, and rudimentary leaves, andnbsp;also the internal structure of the stems and rhizomata,nbsp;and to illustrate the remarkable resemblance of the formsnbsp;and structures to those of the modern Psilotum. Thenbsp;fructification was, however, altogether peculiar, consisting of narrowly ovate sporangia, borne usually in pairs,nbsp;an curved and apparently rigid petioles. Under thenbsp;naicroscope these sporangia show indications of cellularnbsp;structure, and appear to have been membranous in character. In some specimens dehiscence appears to havenbsp;taken place by a slit in one side, and, clay having enterednbsp;into the interior, both walls of the spore-case can be seen.nbsp;In other instances, being flattened, they might be mis-

taken for scales. No spores could be observed in any of the specimens, though in some the surface was markednbsp;by slight, rounded prominences, possibly the impressionsnbsp;of the spores within. This peculiar and very simple style

of spore-case is also characteristic of other species, and gives to Psilophyton a very distinct generic character.nbsp;These naked spore-cases may be compared to those ofnbsp;such lycopodiaceous plants as Psilotum, in which the

scales are rudimentary. They also bear some resemblance, though on a much larger scale, to the spore-cases of somenbsp;Brian ferns {Archmopteris), to be mentioned in thenbsp;sequel. On the whole, however, they seem most nearlynbsp;related to the sporocarps of the Ehizocarpeie.

Arthrostigma, which is found in the same beds with Psilophyton, was a plant of more robust growth, withnbsp;better-developed, narrow, and pointed leaves, borne in anbsp;verticillate or spiral manner, and bearing at the ends ofnbsp;its branches spikes of naked sporocarps, apparently similar to those of Psilophyton but more rounded in form.nbsp;The two genera must have been nearly related, and thenbsp;slender branchlets of Arthrostigma are, unless well pi'e-served, scarcely distinguishable from the stems of Psilophyton. ¹

If, now, we compare the vegetation of these and similar ancient plants with that of modern Ehizoearps, we shall find that the latter still present, though in a depauperated and diminished form, some of the characteristics of their predecessors. Some, like Pilularia, havenbsp;simple linear leaves ; others, like Marsilea, have leaves innbsp;verticils and cuneate in form ; while others, like Azollanbsp;and Palvinia, have frondose leaves, more or less pinnatenbsp;in their arrangement. The first type presents little thatnbsp;is characteristic, but there are in the Brian sandstonesnbsp;and shales great quantities of filamentous and linear objects which it has been impossible to refer to any genus,nbsp;and which might have belonged to plants of the type ofnbsp;Pilularia. It is quite possible, also, that such plants asnbsp;Psilophyton glabrum and Cordaites angustifolia, of whichnbsp;the fructification is quite unknown, may have been alliednbsp;to Ehizoearps. With regard to the verticillate type, wenbsp;are at once reminded of Sphenophyllum (Fig- 20), which

Reporta of the .author on � Devonian Plants,� � Geological Survey of Canada,� which see for details as to Brian Flora of northeastern America.

many palaao-botanists have referred to the Marsiliacm, though, like other Palaeozoic Acrogens, it presents complexities not seen in its modern representatives. 8. pri-mmvwm of Lesquereux is found in the Hudson Kivernbsp;group, and my 8. antiquum in the Middle Erian. Besides these, there are in the Silurian and Erian hedsnbsp;plants with verticillate leaves which have heen placednbsp;with the Annulariae, hut which may have differed fromnbsp;them in fructification. Annularia laxa, of the Erian,nbsp;and Proiannularia HarTcnessii, of the Siluro-Camhrian,nbsp;may he given as examples, and must have heen aquaticnbsp;plants, prohahly allied to Ehizocarps, It is deserving ofnbsp;notice, also, that the two hest-known species of Psilophy-ton (P. princeps and P. robusfius), while allied to Ly-copods hy the structure of the stem and such rudimentarynbsp;foliage as they possess, are also allied, hy the form ofnbsp;their fructification, to the Ehizocarps, and not to ferns,nbsp;as some palseo-hotanists have incorrectly supposed. Anbsp;similar remark applies to Arthrostigma j and the beautifulnbsp;pinnately leaved Ptilophyton may he taken to representnbsp;that type of foliage as seen in modern Ehizocarps, whilenbsp;the allied forms of the Carboniferous which Lesquereuxnbsp;has named Trocliopliyllum, seem to have had sporocarpsnbsp;attached to the stem in the manner of Azolla.

The whole of this evidence, I think, goes to show that in the Erian period there were vast quantities of aquaticnbsp;plants, allied to the modern Ehizocarps, and that the so-called 8porangites referred to in this paper were probablynbsp;the drifted sporocarps and macrospores of some of thesenbsp;plants, or of plants allied to them in structure and habit,nbsp;of which the vegetative organs have perished. I havenbsp;shown that in the Erian period there were vast swampynbsp;flats covered with Psilophyton, and in similar submergednbsp;tracts near to the sea the Protosalvinia may have fillednbsp;the waters and have given off the vast multitudes ofnbsp;macrospores which, drifted by currents, have settled in the

mud of the black shales. We have thus a remarkable example of a group of plants reduced in modern times tonbsp;a few insignificant forms, but which played a great r�le innbsp;the ancient Palaeozoic world.

Leaving the Ehizocarps, we may now turn to certain other families of Erian plants. The first to attract ournbsp;attention in this age would naturally be the Lycopods,nbsp;the club-mosses or ground-pines, which in Canada andnbsp;the Eastern States carpet the ground in many parts ofnbsp;our woods, and are so available for the winter decorationnbsp;of our houses and public buildings. If we fancy one ofnbsp;these humble hut graceful plants enlarged to the dimensions of a tree, we shall have an idea of a Lepidodendron,nbsp;or of any of its allies (Figs. 15, 21). These large lycopo-diaceous trees, which in different specific and genericnbsp;forms were probably dominant in the Erian woods, resembled in general those of modern times in their fruitnbsp;and foliage, except that their cones were large, and probably in most cases with two kinds of spores, and theirnbsp;leaves were also often very long, thus bearing a due proportion to the trees which they clothed. Their thicknbsp;stems required, however, more strength than is necessarynbsp;in their diminutive successors, and to meet this wantnbsp;some remarkable structures were introduced similar tonbsp;those now found only in the stems of plants of highernbsp;rank. The cells and vessels of all plants consist of thinnbsp;�walls of woody matter, enclosing the sap and other contents of these sacs and tubes, and when strength is required it is obtained by lining their interior with successive coats of the hardest form of woody matter, usuallynbsp;known as lignin. But while the walls remain thin, theynbsp;afford free passage to the sap to nourish every part. Ifnbsp;thickened all over, they would become impervious to sap,nbsp;and therefore unsuited to one of their most importantnbsp;functions. These two ends of strength and permeabilitynbsp;are secured by partial linings of lignin, leaving portions of

The most ancient of these contrivances, and one still continued in the world of plants, is that of the barrednbsp;or scalariform vessel. This may be either square or hexagonal, so as to admit of being packed without leavingnbsp;vacancies. It is strengthened by a thick bar of ligneousnbsp;matter up each angle, and these are connected by crossbars so as to form a framework resembling several laddersnbsp;fastened together. Hence the name scalariform, or ladder-like. Now, in a modern Lycopod there is a centralnbsp;axis of such barred vessels associated with simpler fibresnbsp;or elongated cells. Even in SpJienopliyllum and Psilo-pliyton, already referred to as allied to Ehizocarps,¹ therenbsp;is such a central axis, and in the former rigidity is givennbsp;to this by the vascular and woody elements being arranged in the form of a three-sided prism or three-rayednbsp;star. But such arrangements would not suffice for a tree,nbsp;and hence in the arboreal Lycopods of the Brian age anbsp;more complex structure is introduced. The barred vessels were expanded in the first instance into a hollownbsp;cylinder filled in with pith or cellular tissue, and thenbsp;outer rind was strengthened with greatly thickened cells.nbsp;But even this was not sufficient, and in the older stemsnbsp;wedge-shaped bundles of barred tissue were run out fromnbsp;the interior, forming an external woody cylinder, and inside of the rind were placed bundles of tough bast fibres.nbsp;Thus, a stem was constructed having pith, wood, andnbsp;bark, and capable of additions to the exterior of thenbsp;woody wedges by a true exogenous growth. The plan is,nbsp;in short, the same with that of the stems of the exogenousnbsp;trees of modern times, except that the tissues employednbsp;are less complicated. The structures of these remarkable

First noticed by the author, � Journal of Geological Society,� 1865; but more completely by Renault, � Comptes Rendus,� 1870.

trees, and the manner in which they anticipate those of the true exogens of modern times, have been admirablynbsp;illustrated by Dr. Williamson, of Manchester. Hisnbsp;papers, it is true, refer to these plants as existing in thenbsp;Carboniferous age, but there is every reason to believenbsp;that they were of the same character in the Brian. Thenbsp;plan is the same with that now seen in the stems of exogenous phsenogams, and which has long ceased to he usednbsp;in those of the Lycopods. In this way, however, largenbsp;and graceful lycopodiaceous trees were constructed in thenbsp;Brian period, and constituted the staple of its forests.

The roots of these trees were equally remarkable with their stems, and so dissimilar to any now existing thatnbsp;botanists were long disposed to regard them as independent plants rather than roots. They were similar innbsp;general structure to the stems to which they belonged,nbsp;but are remarkable for branching in a very regular manner by bifurcation like the stems above, and for the factnbsp;that their long, cylindrical rootlets were arranged in anbsp;spiral manner and distinctly articulated to the root afternbsp;the manner of leaves rather than of rootlets, and fittingnbsp;them for growing in homogeneous mud or vegetablenbsp;muck. They are the so-called Stigmaria roots, which,nbsp;though found in the Brian and belonging to its lycopo-diaceous plants, attained to far greater importance in thenbsp;Carboniferous period, where we shall meet with them again.

There were different types of lycopodiaceous plants in the Brian. In addition to humble Lycopods like thosenbsp;of our modern woods and great Lepidodendra, which werenbsp;exaggerated Lycopods, there were thick-stemmed and lessnbsp;graceful species with broad rhombic scars {Leptoplileum),nbsp;and others with the leaf-scars in vertical rows {Sigillarid),nbsp;and others, again, with rounded leaf-scars, looking likenbsp;the marks on Stigmaria, and belonging to the genusnbsp;Gyclostigma. Thus some variety was given to the arboreal club-mosses of these early forests. (See Big. 15.)

Another group of plants which attained to great development innbsp;the Brian age is that of the Fernsnbsp;or Brackens. The oldest of thesenbsp;yet known are found in the Middle Brian. The Eopteris of Sa-porta, from the Silurian, at onenbsp;time supposed to carry this typenbsp;much further back, has unfortunately heen found to he a merenbsp;imitative form, consisting ofnbsp;films of pyrites of leaf-like shapes,nbsp;and produced by crystallisation.nbsp;In the Middle Brian, however,nbsp;more especially in North America, many species have been foundnbsp;(Figs. 22 to 24).¹ I have myselfnbsp;recorded more than thirty species from the Middle Brian ofnbsp;Canada, and these belong to several of the genera found in thenbsp;Carboniferous, though some arenbsp;peculiar to the Brian. Of thenbsp;latter, the best known are perhaps those of the genus Archm-opteris (Fig. 24), so abundantnbsp;in the plant-beds of Kiltorcannbsp;in Ireland, as well as in Northnbsp;America. In this genus thenbsp;fronds are large and luxuriant,nbsp;with broad obovate pinnules decurrent on the leaf-stalk, andnbsp;with simple sac-like spore-casesnbsp;borne on modified pinna. Another very beautiful fern found

with Archmopteris is that which I have named Platyphyl-lum, and which grew on a creeping stem or parasitically on stems of other plants, and had marginal fructification.¹

� Reports on Fossil Plants of the Devonian and Upper Silurian of Canada,� 18Y1, amp;c.

Another very remarkable fern, which some botanists have supposed may belong to a higher group than the ferns, isnbsp;Megalopteris (Fig. 26).

Some of the Brian ferns attained to the dimensions of tree-ferns. Large stems of these, which must have floatednbsp;out far from land, have been found by Newberry in thenbsp;marine limestone of Ohio {Caulopteris antiqua and C.nbsp;peregrina, Newberry),* and Prof. Hall has found in the

Upper Devonian of Gilboa, New York, the remains of a forest of tree-ferns standing in situ with their greatnbsp;masses of aerial roots attached to the soil in which theynbsp;grew {Caulopteris Lochwoodi, Dn.).t

These aerial roots introduce us to a new contrivance for strengthening the stems of plants by sending out intonbsp;the soil multitudes of cord-like cylindrical roots from

various heights on the stem, and which form a series of stays like the cordage of a ship. This method of support

still continues in the modern tree-ferns of the tropics and the southern hemisphere. In one kind of tree-fern

stem from the Erian of Eew York, there is also a special arrangement for support, consisting of a series of peculiarly arranged radiating plates of scalariform Tessels, notnbsp;exactly like those of an exogenous stem, but doing dutynbsp;for it {A steropieris).¹

Similar plants have been described fromnbsp;the Erian of Ealken-berg, in Germany,nbsp;and of Saalfeld, innbsp;Thuringia, by Goep-pert and Unger, andnbsp;are referred to fernsnbsp;by the former, butnbsp;treated as doubtfulnbsp;by the latter, f Thisnbsp;peculiar type of tree-fern is apparently anbsp;precursor of the morenbsp;exogenous type ofnbsp;Heterangium, recently described and referred to ferns bynbsp;Williamson. Here,nbsp;again, we have a mechanical contrivancenbsp;now restricted tonbsp;higher plants appropriated by these oldnbsp;cryptogams.

The history of the ferns in geological time is remarkably different from that of the Lycopods; for while the

�Journal of the Geological Society,� London, 1881. t �Sphenopteris Refracta,� Goeppert; �Flora des Uebergangsge-birges.� � Cladoxylon Mirabile,� Unger; � Paloeontologie des Thuringernbsp;W aides.�

The family of the Equisetacem, ornbsp;mare�s-tails, was alsonbsp;represented by largenbsp;species of Calamitesnbsp;and by Asterophyl-Utes in the Erian ;nbsp;hut, as its headquarters are in the Carboniferous, we maynbsp;defer its consideration till the nextnbsp;chapter. (Figs. 27,nbsp;28.)

Passing over these for the present, wenbsp;find that the flowering plants are represented in the Eriannbsp;forests by at leastnbsp;two types of Gym-nosperms, that ofnbsp;Taxinm or yews,nbsp;and an extinct family, that of the Cordaites (Figs. 30, 31).nbsp;The yew-trees are closely allied to the pines and spruces,nbsp;and are often included with them in the family of ConiferoB.nbsp;They differ, however, in the habit of producing berries ornbsp;drupe-like fruits instead of cones, and there is somenbsp;reason to believe that this was the habit of the Eriannbsp;trees of this group, though their wood in some instances resembles rather that of the Araucaria, or Nor-

folk Island pine, than that of the modern yews. These trees are chiefly known to us by their mineralised trunks,nbsp;which are often found like drift-wood on modern sandbanks embedded in the Erian sandstones or limestones.nbsp;It often shows its structure in the most perfect manner in specimens penetrated by calcite or silica, or bynbsp;pyrite, and in which the original woody matter has

Fig. 29.�JJadoxylon Ouangondianum^ an Erian conifer, a. Fragment showing Sternbergia pith and wood* a, medullary sheath; pith;nbsp;wood; section of pith, b, Wood-cell; a, hexagonal areole;nbsp;pore, c, Longitudinal section of wood, showing, a, areolation, andnbsp;�, medullary rays, n, Transverse section, showing, a, wood-cells, andnbsp;hf limit of layer of growth, (b, c, d, highly magnified,)

been resolved into anthracite or even into graphite. These trees have true woody tissues presenting that beautiful arrangement of pores or thin parts enclosed in cuplike discs, which is characteristic of the coniferous trees,nbsp;and which is a great improvement on the barred tissuenbsp;already referred to, affording a far more strong, tough,

These primitive pines make their appearance in the Middle Brian, in various parts of America, as well as innbsp;Scotland and Germany, and they are represented by woodnbsp;indicating the presence of several species. I have myselfnbsp;indicated and described five species from the Brian ofnbsp;Canada and the United States. From the fact that thesenbsp;trees are represented by drifted trunks embedded in sandstones and marine limestones, we may, perhaps, infer thatnbsp;they grew on the rising grounds of the Brian land, andnbsp;that their trunks were carried by river-fioods into the sea.nbsp;Uo instance has yet certainly occurred of the discovery ofnbsp;their foliage or fruit, though there are some fan-shapednbsp;leaves usually regarded as ferns which may have belongednbsp;to such trees. These in that case would have resemblednbsp;the modern Qingho of China, and some of the fruits referred to the genus Cardiocarpum may have been produced by them. Various names have been given to thesenbsp;trees. I have preferred that given by Unger, Dadoxylon,nbsp;as being more non-committal as to affinities than thenbsp;others.¹ Many of these trees had very long internalnbsp;pith-cylinders, with curious transverse tubulse, and which,nbsp;when preserved separately, have been named Sternhergia.

Allied to these trees, and perhaps intermediate between them and the Cycads, were those known as Cordaitesnbsp;(Fig. 30), which had trunks resembling those of Dadoxylon, but with still larger Sternhergia piths and an internalnbsp;axis of scalariform vessels, surrounded by a comparativelynbsp;thin woody cylinder. Some of them have leaves over anbsp;foot in length, reminding one of the leaves of broad-leavednbsp;grasses or iridaceous plants. Yet their flowers and fruitnbsp;seem to have been more nearly allied to the yews than tonbsp;any other plants (Fig. 31). Their stems were less woody

and their piths larger than in the true pines, and some of the larger-leaved species must have had thick, stiffnbsp;branches. They are regarded as constituting a separatenbsp;family, intermediate between pines and cycads, and, be-

ginning in the Middle Devonian, they terminate in the Permian, where, however, some of the most gigantic species occur. In so far as the form and structure of thenbsp;leaves, stems, and fruit are concerned, there is marvellously little difference between the species found in the

Erian and the Permian. They culminated, however, in the Carboniferous period, and the coal-fields of southernnbsp;France have proved so far the richest in their remains.

Lastly, a single specimen, collected by Prof. James Hall, of Albany, at Eighteen-mile Creek, Lake Erie, hasnbsp;the structure of an ordinary angiospermous exogen, andnbsp;has been described by me as Syringoxylon mirabile¹

This unique example is sufficient to establish the fact of the existence of such plants at this early date, unless somenbsp;accident may have carried a specimen from a later forma-

tion to be mixed with Erian fossils. It is to be observed, however, that the non-occurrence of any similar wood innbsp;all the formations between the Upper Erian and the Middle Cretaceous suggests very grave doubt as to the authenticity of the specimen. I record the fact, waiting furthernbsp;discoveries to confirm it. Of the character of the specimen which I have described I entertain no doubt.

We shall be better able to realise the significance and relations of this ancient flora when we have studied thatnbsp;of the succeeding Carboniferous. We may merely remarknbsp;here on the fact that, in these forests of the Devoniannbsp;and in the marshes on their margins, we find a wonderful expansion of the now modest groups of Ehizocarpsnbsp;and Lyeopods, and that the flora as a whole belongs tonbsp;the highest group of Cryptogams and the lowest of Phae-nogams, so that it has about it a remarkable aspect ofnbsp;mediocrity. Further, while there is evidence of somenbsp;variety of station, there is also evidence of much equalitynbsp;of climate, and of a condition of things more resemblingnbsp;that of the insular climates of the temperate portions ofnbsp;the southern hemisphere than that of INTorth America ornbsp;Europe at present.

The only animal inhabitants of these Devonian woods, so far as known, were a few species of insects, discoverednbsp;by Hartt in New Brunswick, and described by Dr. Scud-der. Since, however, we now know that scorpions asnbsp;well as insects existed in the Silurian, it is probable thatnbsp;these also occurred in the Erian, though their remainsnbsp;have not yet been discovered. All the known insects ofnbsp;the Eriaii woods are allies of the shad-flies and grasshoppers {Neuroptera and Orthoptera), or intermediate between the two. It is probable that the larvae of most ofnbsp;them lived in water and fed upon the abundant vegetablenbsp;matter there, or on the numerous minute crustaceans andnbsp;worms. There were no land vertebrates, so far as known,nbsp;but there were fishes {Dipterus, etc.), allied to the mod-

ern Barramunda or Ceratodus of Australia, and with teeth suited for grinding vegetable food. It is also possible that some of the smaller plate-covered fishes (Placo-ganoids, like PtericMIiys) might have fed on vegetablenbsp;matter, and, in any case, if they fed on lower animals, thenbsp;latter must have subsisted on plants. I mention thesenbsp;facts to show that the superabundant vegetation of thisnbsp;age, whether aquatic or terrestrial, was not wholly uselessnbsp;to animals. It is quite likely, also, that we have yetnbsp;much to learn of the animal life of the Brian swamps andnbsp;woods.

It is, of course, very unsatisfactory to give names to mere fragments of plants, yet it seems very desirable to have some means of arranging them. With respect to the organisms described above,nbsp;which were originally called by me Sporangites, under the supposition that they were Sporangia rather than spores, this namenbsp;has so far been vindicated by the discovery of the spore-cases belonging to them, SO' that I think it may still be retained as a provisionalnbsp;name; but 1 would designate the whole as Protosalvinice, meaningnbsp;thereby plants with rhizoearpean affinities, though possibly whennbsp;better understood belonging to different genera. We may undernbsp;these names speak of their detached discs as macrospores and ofnbsp;their cellular envelopes as sporocarps. The following may be recognized as distinct forms:

1. Protosalvinia Huronensis, Dawson, Syn., Sporangites Huron-ensis, � Report on Brian Flora of Canada,� 1871.�Macrospores, in the form of discs or globes, smooth and thick-walled, the walls penetrated by minute radiating pores. Diameter about one one-hundredth of an inch, or a little more, When in situ several macrospores are contained in a thin cellular sporocarp, probably globularnbsp;in form. From the Upper Brian, and perhaps Lower Carboniferousnbsp;shales of Kettle Point, Lake Huron, of various places in the State ofnbsp;Ohio, and in the shale boulders of the boulder clay of Chicago andnbsp;vicinity. First collected at Kettle Point by Sir W. E. Logan, and

in Ohio by Prof. Edward Orton, and at Chicago by Dr. H. A. Johnson and Mr. B. W. Thomas, also in New York by Prof. J. M. Clarke.

The macrospores collected by Mr. Thomas from the Chicago clays and shales conform closely to those of Kettle Point, and probably belong to the same species. Some of them are thicker in thenbsp;outer wall, and show the pores much more distinctly. These havenbsp;been called by Mr. Thomas S. Ghicagoensis, and may be. regarded asnbsp;a varietal form. Specimens isolated from the shale and mountednbsp;dry, show what seems to have been the hilum or scar of attachmentnbsp;better than those in balsam.

Sections of the Kettle Point shale show, in addition to the macrospores, wider and thinner shreds of vegetable matter, which I am inclined to suppose to be remains of the sporocarps.

2. nbsp;nbsp;nbsp;Protosalvinia (Sporangites) Braziliensis, Dawson, � Canadiannbsp;Record of Science,� 1883.�Macrospores, round, smooth, a littlenbsp;longer than those of the last species, or about one seventy-fifth ofnbsp;an inch in diameter, enclosed in round, oval, or slightly reniformnbsp;sporocarps, each containing from four to twenty-four macrospores.nbsp;Longest diameter of sporocarps three to six millimetres. Structurenbsp;of wall of sporocarps hexagonal cellular. Some sporocarps show nonbsp;maorospores, and may possibly contain microspores. The specimensnbsp;are from the Brian of Brazil. Discovered by Mr. Orville Derby.nbsp;The formation, according to Mr. Derby, consists of black shales below, about three hundred feet thick, and containing the fueoid knownnbsp;as Spirophyton, and probably decomposed vegetable matter. Abovenbsp;this is chocolate and reddish sliale, in which the well-preserved specimens of Protosalvinia occur. These beds are very widely distributed,nbsp;and abound in Protosalvinia and Spirophyton.

3. nbsp;nbsp;nbsp;Protosalvinia (Sporangites) hilobata, Dawson, �Canadiannbsp;Record of Science,� 1883.�Sporocarps, oval or reniform, threenbsp;to six millimetres in diameter, each showing two ronndednbsp;prominences at the ends, with a depression in the middle, andnbsp;sometimes a raised neck or isthmus at one side connecting thenbsp;prominences. Structure of sporocarp cellular. Some of the specimens indicate that each prominence or tubercle contained severalnbsp;macrospores. At first sight it would be easy to mistake these bodiesnbsp;for valves of Beyrichia.

Pound in the same formations with the last species, though, in so far as the specimens indicate, not precisely in the same beds. Collected by Mr. Derby.

4. nbsp;nbsp;nbsp;Protosalvinia ClarJcei, Dawson, P. bilobata, Clarke, � Americannbsp;Journal of Science.��Macrospores two-thirds to one millimetre in

diameter. One, two, or three contained in each sporooarp, which is cellular. The macrospores have very thick walls with radiating tortuous tubes. Unless this structure is a result of mineral crystallisation, these macrospores must have had very thick walls and must havenbsp;resembled in structtire the thickened cells of stone fruits and of thenbsp;core of the pear, or the tests of the Silurian and Brian seeds knownnbsp;as Pachytheca, though on a smaller scale.

It is to bo observed that bodies similar to these occur in the Boghead earthy bitumen, and have been described by Credner.

1 have found similar bodies in the so-called � Stellar coal � of the coal district of Piotou, Nova Scotia, some layers of which are fillednbsp;with them. They occur in groups or patches, which seem to be enclosed in a smooth and thin membrane or sporocarp. It is quitenbsp;likely that these bodies are generically distinct from Protosalvinia.

5. Protosalvinia punctata, Newton, � Geological Magazine,� New Series, December 2d, vol. ii.�Mr. Newton has named the discsnbsp;found in the white coal and Tasmanite, Tasmanites, the species being Tasmanites punctatus, but as my name SporangiUs had priority,nbsp;I do not think it necessary to adopt this term, though there can benbsp;little doubt that these organisms are of similar character. The samenbsp;remark may be made with reference to the bodies described by Huxley and Newton as occurring in the Better-bed coal.

In Witham�s �Internal Structure of Fossil Vegetables,� 1833, Plate XI, are figures of Lancashire cannel which shows Sporangites ofnbsp;the type of those in the Brian shales. Quekett, in his � Eeport on thenbsp;Torbane Hill Mineral,� 1854, has very well figured similar structuresnbsp;from the Methel coal and the Lesmahagow cannel coal. These arenbsp;the earliest publications on the subject known to me; and Quekett,nbsp;though not understanding the nature of the bodies he observed,nbsp;holds that they are a usual ingredient in cannel coals.

{Lycopodites Vanuzemii of �Report on Devonian and Upper Silurian Plants,� Part I., page 35. L. plumula of � Report on Lowernbsp;Carboniferous Plants,� page 24, Plate I., Pigs. 7, 8, 9.) In the reports above referred to, these remarkable pinnate, frond-like objectsnbsp;were referred to the genus Lycopodites, as had been done by Goep-pert in his description of the European species Lycopodites pennce-formis, which is very near to the American Brian form. Since 1871,nbsp;however, there have been many new specimens obtained, and verynbsp;various opinions expressed as to their affinities. While Hall hasnbsp;named some of them Plumalina, and has regarded them as animal

structures, allied to hydroids, Lesquereux has described some of the Carboniferous forms under the generic name Troefwphyllum, whichnbsp;is, however, more appropriate to plants with verticillate leaves whichnbsp;are included in this genus. Before I had seen the publications ofnbsp;Hall and Lesquereux on the subject, I had in a paper on � Scottishnbsp;Devonian Plants � ¹ separated this group from the genus Lycopodites,nbsp;and formed for it the genus Ptilophyton, in allusion to the featherlike aspect of the species. My reasons for this, and my present information as to the nature of these plants, may be stated, as follows:

Schimper, in his � Palteontologie Vegetale� (possibly from inattention to the descriptions or want of access to specimens), doubts the lycopodiaceous character of species of Lycopodites described in mynbsp;published papers on plants of the Devonian of America and in mynbsp;Report of 1871. Of these, L. Richardsoni and L. Matthewi are undoubtedly very near to the modern genus Lycopodium. L. Vanux-emii is, I admit, more problematical; but Schimper could scarcelynbsp;have supposed it to be a fern or a fucoid allied to Caulerpa had henbsp;observed that both in my species and the allied L. pennceformis ofnbsp;Goeppert, which he does not appear to notice, the pinnules are articulated upon the stem, and leave scars where they have fallen off.nbsp;When in Belfast in 1870, my attention was again directed to thenbsp;affinities of these plants by finding in Prof. Thomson�s collection anbsp;specimen from Caithness, which shows a plant apparently of thisnbsp;kind, with the same long narrow pinn� or leaflets, attached, however; to thicker stems, and rolled up in a circinate manner. It seemsnbsp;to be a plant in vernation, and the parts are too much crowded andnbsp;pressed together to admit of being accurately figured or described;nbsp;but 1 think I can scarcely be deceived as to its true nature. Thenbsp;circinate arrangement in this case would favour a relationship tonbsp;ferns; but some lycopodiaceous plants also roll themselves in thisnbsp;way, and so do the branches of the plants of the genus Psilophyton.nbsp;(Pig. 17, supra.)

The specimen consists of a short, erect stem, on which are placed somewhat stout alternate branches, extending obliquely outward andnbsp;then curving inward in a circinate manner. The lower ones appearnbsp;to produce on their inner sides short lateral branchlets, and uponnbsp;these, and also upon the curved extremities of the branches, are long,nbsp;narrow, linear leaves placed in a crowded manner. The specimen isnbsp;thus not a spike of fructification, but a young stem or branch in vernation, and which when unrolled would be of the form of those

peculiar pinnate Lyeopodttes of which L. Vanuxemii of the American Devonian and L. pennmformis of the European Lower Carboniferous are the types, and it shows, what might have been anticipated from other specimens, that they were low, tufted plants, circinate innbsp;vernation. The short stem of this plant is simply furrowed, andnbsp;bears no resemblance to a detached branch of Lyeopodites MilUrinbsp;which lies at right angles to it on the same slab. As to the affinitiesnbsp;of the singular type of plants to which this specimen belongs, I maynbsp;quote from my � Report on the Lower Carboniferous Plants ofnbsp;Canada,� in which 1 have described an allied species, h. plumula:

� The botanical relations of these plants must remain subject to doubt, until either their internal structure or their fructification cannbsp;be discovered. In the mean time I follow Goeppert in placing themnbsp;in what we must regard as the provisional genus Lyeopodites. Onnbsp;the one hand, they are not unlike the slender twigs of Taxodiumnbsp;and similar Conifers, and the highly carbonaceous character of thenbsp;stems gives some colour to the supposition that they may have beennbsp;woody plants. On the other hand, they might, so far as form is concerned, be placed with Alga3 of the type of Brongniart�s Chondritesnbsp;obtmus, or the modern Caulerpa plumaria. Again, in a plant ofnbsp;this type from the Devonian of Caithness to which I have referred innbsp;a former memoir, the vernation seems to have been circinate, andnbsp;Schimper has conjectured that these plants may be ferns, whichnbsp;seems also to have been the view of Shumard.�

On the whole, these plants are allied to Lycopods rather than to ferns; and as they constitute a small but distinct group, known only,nbsp;so far as I am aware, in the Lower Carboniferous and Brian or Devonian, they deserve a generic name, and I proposed for them in mynbsp;�Paper on Scottish Devonian Plants,� 1878, that of Ptilophyton, a,nbsp;name sufficiently distinct in sound from Psilophyton, and expressingnbsp;very well their peculiar feather-like habit of growth. The genus wasnbsp;defined as follows;

� Branching plants, the branches bearing long, slender leaves in two or more ranks, giving them a feathered appearance; vernationnbsp;circinate. Fruit unknown, but analogy would indicate that it wasnbsp;borne on the bases of the leaves or on modified branches with shorternbsp;leaves.�

The Scottish specimen above referred to was named Pt. Thom-soni, and was characterised by its densely tufted form and thick branches. The other species known are: Pt. pennwformis, Goeppert, L. Carboniferous; Pt. Vanuxemii, Dawson, Devonian; Pt.nbsp;plumula, Dawson, L. Carboniferous.

Shumard�s Filicites gracilis, from the Devonian of Ohio, and Star�s Pinites antecedens, from the Lower Carboniferous of Silesia,nbsp;may possibly belong to the same genus. The Scottish specimen referred to is apparently the first appearance of this form in thenbsp;Devonian of Europe.

I have at a still later date had opportunities of studying considerable series of these plants collected by Prof. Williams, of Cornell University, and prepared a note in reference to them for the American Association, of which, however, only an abstract has been published. I have also been favoured by Prof. Lesquereux and Mr.nbsp;Lacoe, of Pittston, with the opportunity of studying the specimensnbsp;referred to Trochophyllum.

Prof. Williams�s specimens occur in a dark shale associated with remains of land-plants of the genera Psilophyton, Phodea, amp;c., andnbsp;also marine shells, of which a small species of Rhynchomlla is oftennbsp;attached to the stems of the Ptilophyton. Thus these organismsnbsp;have evidently been deposited in marine beds, but in associationnbsp;with land-plants.

The study of the specimens collected by Prof. Williams develops the following facts: (1) The plants are not continuous fronds, butnbsp;slender stems or petioles, with narrow, linear leaflets attached in anbsp;pinnate manner. (2) The pinnules are so articulated that they breaknbsp;off, leaving delicate transverse scars, and the lower parts of the stemsnbsp;are often thus denuded of pinnie for the length of one or morenbsp;inches. (3) The stems curve in such a manner as to indicate a cir-cinate vernation. (4) In a few instances the fronds were observednbsp;to divide dichotomously toward the top; but this is rare. (5) Therenbsp;are no indications of cells in the pinnules; but, on the other hand,nbsp;there is no appearance of fructification unless the minute granniesnbsp;which roughen some of the stems are of this nature. (C) The stemsnbsp;seem to have been lax and flexuous, and in some instances theynbsp;seem to have grown on the petioles of ferns preserved with them innbsp;the same beds. (7) The frequency of the attachment of small brachio-pods to the specimens of Ptilophyton would seem to indicate thatnbsp;the plant stood erect in the water. (8) Some of the specimens shownbsp;so much carbonaceous matter as to indicate that the pinnules werenbsp;of considerable consistency. All these characters are those rathernbsp;of an aquatic plant than of an animal organism or of a land-plant.

The specimens communicated by Prof. Lesquereux and Mr. Lacoe are from the Lower Carboniferous, and evidently represent anbsp;different species with similar slender pitted stems, often partiallynbsp;denuded of pinnules below; but the pinnules are much broader and

more distant. They are attached by very narrow bases, and apparently tend to lie on a plane, though they may possibly have been spirally arranged. On the same slabs are rounded sporangia ornbsp;macrospores like those of Lepidodendron, but there is no evidencenbsp;that these belonged to Trochophyllum. On the stems of this plant,nbsp;however, there are small, rounded bodies apparently taking the placesnbsp;of some of the pinnules. These may possibly be spore-cases; butnbsp;they may be merely imperfectly developed pinnules. Still the factnbsp;that similar small granules appear on the stems of the Devoniannbsp;species, favours the idea that they may be organs of fructification.

The most interesting discovery,, however, which results from the study of Mr. Lacoe�s specimens, is that the pinnules were cylindricalnbsp;and hollow, and probably served to float the plant. This wouldnbsp;account for many of the peculiarities in the appearance and modenbsp;of occurrence of the Devonian Ptilophyion, which are readily explained if it is supposed to be an aquatic plant, attaching itself tonbsp;the stems of submerged vegetable remains and standing erect in thenbsp;�water by virtue of its hollow leaves. It may well, however, havenbsp;been a plant of higher organisation than the Algae, though no doubtnbsp;cryptogamous.

The species of Ptilop'hyton will thus constitute a peculiar group of aquatic plants,, belonging to the Devonian and Lower Carboniferous periods, and perhaps allied to Lycopods and Pillworts in theirnbsp;organisation and fruit, but specially distinguished by their linearnbsp;leaves serving as floats and arranged pinnately on slender stems.nbsp;The only species yet found within the limits of Canada is Pt. plu-mula, found by Dr. Honeyman in the Lower Carboniferous of Novanbsp;Scotia; but as Pt. Vanuxemii abounds in the Erian of New York,nbsp;it will no doubt be found in Canada also.

As the fact of the occurrence of true tree-ferns in rocks so old as the Middle Erian or Devonian has been doubted in some quarters, the following summary is given from descriptions published innbsp;the �Journal of the Geological Society of London� (1871 and 1881),nbsp;where figures of the species will be found:

Of the numerous ferns now known in the Middle and Upper Devonian of North America, a great number are small and delicatenbsp;species, which were probably herbaceous; but there are other speciesnbsp;which may have been tree-ferns. Little definite information, however, has, until recently, been obtained with regard to their habit ofnbsp;growth.

The only species known to me in the Devonian of Europe is the Caulopteris PeacJiii of Salter, figured in the ¹� Quarterly Journal ofnbsp;the Geological Society � for 1858. The original specimen of this Inbsp;had an opportunity of seeing in London, through the kindness ofnbsp;Mr. Etheridge, and have no doubt that it is the stem of a smallnbsp;arborescent fern, allied to the genus Caulopteris, of the coal formation.

In my paper on the Devonian of Eastern America (� Quarterly Journal of the Geological Society,� 1862), I mentioned a plant foundnbsp;by Mr. Richardson at Perry, as possibly a species of Megaphyton,nbsp;using that term to denote those stems of tree-ferns which have thenbsp;leaf-scars in two vertical series; but the specimen was obscure, andnbsp;I have not yet obtained any other.

More recently, in 1869, Prof. Hall placed in my hands an interesting collection from Gilboa, New York, and Madison County, New York, including two trunks surrounded by aerial roots, which I havenbsp;described as Psaronius textilis and P. Erianus, in my � Revision ofnbsp;the Devonian Flora,� read before the Royal Society.¹ In the samenbsp;collection were two very large petioles, Phaehiopteris gigantea andnbsp;if. palmata, which I have suggested may have belonged to tree-ferns.

My determination of the species of Psaronius, above mentioned, has recently been completely confirmed by the discovery on the partnbsp;of Mr. Lockwood, of Gilboa, of the upper part of one of these stems,nbsp;with its leaf-scars preserved and petioles attached, and also by somenbsp;remarkable specimens obtained by Prof. Newberry, of New York^nbsp;from the Corniferous limestone of Ohio, which indicate the existence there of three species of tree-ferns, one of them with aerialnbsp;roots similar to those of the Gilboa specimens. The whole of thesenbsp;specimens Dr. Newberry has kindly allowed me to examine, and hasnbsp;permitted me to describe the Gilboa specimen, as connected withnbsp;those which I formerly studied in Prof. Hall�s collections. Thenbsp;specimens from Ohio he has himself named, but allows me to noticenbsp;them here by way of comparison with the others. I shall add somenbsp;notes on specimens found with the Gilboa ferns.

It may be further observed that the Gilboa specimens are from a bed containing erect stumps of tree-ferns, in the Chemung groupnbsp;of the Upper Devonian, while those from Ohio are from a marinenbsp;limestone, belonging to the lower part of the Middle Devonian.

Abstract in � Proceedings of the Royal Society,� May, 1810; also �Report on Brian Plants of Canada,� 1811.

inches in diameter, rugose longitudinally. Leaf-scars broad, rounded above, and radiatingly rugose, with an irregular scar below, arrangednbsp;spirally in about five ranks; vascular bundles not distinctly preserved. Petioles slender, much expanded at the base, dividing atnbsp;first in a pinnate manner, and afterwards diohotomously. Ultimatenbsp;pinn� with remains of numerous, apparently narrow pinnules.

This stem is probably the upper part of one or other of the species of Psaroniua found in the same bed (P. Erianus, Dawson,nbsp;and P. textilis, Dawson).¹ It appears to have been an erect stemnbsp;embedded in situ in sandstone, and preserved as a cast. The stemnbsp;is small, being only two inches, or a little more, in diameter. Itnbsp;is coarsely wrinkled longitudinally, and covered with large leaf-scars, each an inch in diameter, of a horseshoe-shape. The petioles, five of which remain, separate from these soars with a distinctnbsp;articulation, except at one point near the base, where probably anbsp;bundle or bundles of vessels passed into the petiole. They retainnbsp;their form at the attachment to the stem, but a little distancenbsp;from it they are fiattened. They are inflated at the base, and somewhat rapidly diminish in size. The leaf-sears vary in form, and arenbsp;not very distinct, but they appear to present a semicircular row ofnbsp;pits above, largest in the middle. From these there proceed downward a series of irregular furrows, converging to a second and morenbsp;obscure semicircle of pits, within or below which is the irregular soarnbsp;or break above referred to. The attitude and form of the petiolesnbsp;will be seen from Pig. 34, supra.

The petioles are broken off within a few inches of the stem; but other fragments found in the same beds appear to show theirnbsp;continuation, and some remains of their foliage. One specimennbsp;shows a series of processes at the sides, which seem to be the remains of small pinn�, or possibly of spines on the margin of thenbsp;petiole. Other fragments show the division of the frond, at first innbsp;a pinnate manner, and subsequently by bifurcation; and some fragments show remains of pinnules, possibly of fertile pinnules. Thesenbsp;are very indistinct, but would seem to show that the plant approached, in the form of its fronds and the arrangement of itsnbsp;fructification, to the Cyclopterids of the subgenus AneimiUa, one ofnbsp;which (Aneimites Acadica), from the Lower Carboniferous of Novanbsp;Scotia, I have elsewhere described as probably a tree-fern, f The

fronds were evidently different from those of Archmopteris¹ a genus characteristic of the same beds, but of very different habit of growth.nbsp;This accords with the fact that there is in Prof. Hall�s collection anbsp;mass of fronds of Cyclopteris (Archmopteris) Jacksoni, so arrangednbsp;as to make it probable that the plant was an herbaceous fern, producing tufts of fronds on short stems in the ordinary way. Thenbsp;obscurity of the leaf-scars may render it doubtful whether the plantnbsp;above described should be placed in the genus Caulopteris or in Stem-matopteria; but it appears most nearly allied to the former. Thenbsp;genus is at present, of course, a provisional one; but I have thoughtnbsp;it only justice to the diligent labours of Mr. Lockwood to namenbsp;this curious and interesting fossil Caulopteris Lockivoodi.

I have elsewhere remarked on the fact that trunks, and petioles, and pinnules of ferns are curiously dissociated in the Devonian bedsnbsp;�an effect of water-sorting, characteristic of a period in which thenbsp;conditions of deposition were so varied. Another example of thisnbsp;is, that in the sandstones of Gasp� Bay, which have not as yet afforded any example of fronds of ferns, there are compressed trunks,nbsp;which Mr. Lockwood�s specimens allow me at least to conjecturenbsp;may have belonged to tree-ferns, although none of them are sufficiently perfect for description.

Mr. Lockwood�s collection includes specimens of Psaro?nus tex-tilis ; and in addition to these there are remains of erect stems somewhat different in character, yet possibly belonging to the higher parts of the same species of tree-fern. One of these is a stem crushed innbsp;such a manner that it does not exhibit its form with any distinctness,nbsp;but surrouuded by smooth, cylindrical roots, radiating from it innbsp;bundles, proceeding at first horizontally, and then curving downward, and sometimes terminating in rounded ends. They resemblenbsp;in form and size the aerial roots of Psaronius Erianua ; and I believenbsp;them to be similar roots from a higher part of the stem, and somenbsp;of them young and not prolonged sufficiently far to reach the ground.nbsp;This specimen would thus represent the stem of P. Eriarms at anbsp;higher level than those previously found. We can thus in imagination restore the trunk and crown of this once graceful tree-fern,nbsp;though we have not the detail of its fronds. Mr. Lockwood�snbsp;collections also contain a specimen of the large fern-petiole whichnbsp;I have named Rliaehiopteris punctata. My original specimennbsp;was obtained by Prof. Hall from the same horizon in New York.

The genus to which the well-known Cyclopteris (Adiantites) Hiber-nicus of the Devonian of Ireland belongs.

That of Mr. Lockwood is of larger size, but retains no remains of the frond. It must have belonged to a species quite distinct from Cau-lopteris Loekwoodi, but which may, like it, have been a tree-fern.

3. Cmdopteris antiqua, Newberry.�This is a flattened stem, on a slab of limestone, containing Brachiopods, Trilobites, amp;c., of thenbsp;Corniferous limestone. It is about eighteen inches in length, andnbsp;three and a half inches in average breadth. The exposed side showsnbsp;about twenty-two large leaf-scars arranged spirally. Each leaf,nbsp;where broken off, has left a rough fracture; and above this is anbsp;semicircular impression of the petiole against the stem, which, asnbsp;well as the surface of the bases of the petioles, is longitudinallynbsp;striated or tuberculated. The structures are not preserved, butnbsp;merely the outer epidermis, as a coaly film. The stem altogethernbsp;much resembles Gaulopteria PeacMi, but is of larger size. It differsnbsp;from C. Loekwoodi in the more elongated leaf-bases, and in thenbsp;leaves being more remotely placed; but it is evidently of the samenbsp;general character with that species.

3. Caulopieris {Protopteris) peregrina, Newberry. � This is a much more interesting species than the last, as belonging to a generic or subgeneric form not hitherto recognised below the Carboniferous, and having its minute structure in part preserved.

The specimens are, like the last, on slabs of marine limestone of the Corniferous formation, and flattened. One represents an uppernbsp;portion of the stem with leaf-scars and remains of petioles; anothernbsp;a lower portion, with aerial roots. The upper part is three inchesnbsp;in diameter, and about a foot in iength, and shows thirty leaf-scars,nbsp;which are about three-fourths of an inch wide, and rather less innbsp;depth. The upper part presents a distinct rounded and sometimesnbsp;double marginal line, sometimes with a slight depression in the middle. The lower part is irregular, and when most perfect shows sevennbsp;slender vascular bundles, passing obliquely downward into the stem.nbsp;The more perfect leaf-bases have the structure preserved, and shownbsp;a delicate, thin-walled, oval parenchyma, while the vascular bundlesnbsp;show soalariform vessels with short bars in several rows, in the manner of many modern ferns. Some of the scars show traces of thenbsp;hippocrepian mark characteristic of Protopteris; and the arrangement of the vascular bundles at the base of the scars is the same asnbsp;in that genus, as are also the general form and arrangement of thenbsp;scars. On careful examination, the species is indeed very near to thenbsp;typical P. Sternbergii, as figured by Corda and Schimper.*

The genus Protopteris of Sternberg, though the original species (P. punctata) appears as a Lepidodendron in his earlier plate (Platenbsp;4), and as a Sigillaria (S. punctata) in Brongniart�s great work, is anbsp;true tree-fern; and the structure of one species (P. Cottai) has beennbsp;beautifully flguered by Corda. The species hitherto described arenbsp;from the Carboniferous and Permian.

The second specimen of this species represents a lower part of the stem. It is thirteen inches long and about four inches in diameter, and is covered with a mass of flattened aerial roots lying parallel to each other, in the manner of the Psaronites of the coal-formation and of P. Erianus of the Upper Brian or Devonian.

4. Asteropteris noveboracensis, gen. and sp. n.�The genus As-teropteris is established for stems of ferns having the axial portion composed of vertical radiating plates of scalariform tissue embeddednbsp;in parenchyma, and having the outer cylinder composed of elongatednbsp;cells traversed by leaf-bundles of the type of those of Zygopteris.

The only species known to me is represented by a stem 2'5 centimetres in diameter, slightly wrinkled and pitted externally, perhaps by traces of aerial roots which have perished. The transverse section shows in the centre four vertical plates of scalariform or imperfectly reticulated tissue, placed at right angles to each other, andnbsp;united in the middle of the stem. At a short distance from thenbsp;centre, each of these plates divides into two or three, so as to formnbsp;an axis of from ten to twelve radiating plates, with remains of cellular tissue filling the angular interspaces. The greatest diameter ofnbsp;this axis is about 1�5 centimetre. Exterior to the axis the stem consists of elongated cells, with somewhat thick walls, and more densenbsp;toward the circumference. The walls of these cells present a curiousnbsp;reticulated appearance, apparently caused by the cracking of thenbsp;ligneous lining in consequence of contraction in the process of carbonization. Embedded in this outer cylinder are about twelve vascular bundles, each with a dumb-bell-shaped group of scalariformnbsp;vessels enclosed in a sheath of thick-walled flbres. Each bundle isnbsp;opposite to one of the rays of the central axis. The specimen showsnbsp;about two inches of the length of the stem, and is somewhat bent,nbsp;apparently by pressure, at one end.

This stem is evidently that of a small tree-fern of a type, so far as known to me, not before described,¹ and constituting a verynbsp;complex and symmetrical form of the group of Palffiozoic ferns allied

Prof. Williamson, to whom I have sent a tracing of the structure, agrees with me that it is new.

to the genus Zygopteris of Schimper. The central axis alone has a curious resemblance to the peculiar stem described by Unger (�- Devonian Flora of Thuringia �) under the name of Cladoxylon mira-bile; and it is just possible that this latter stem may be the axisnbsp;of some allied plant. The large aerial roots of some modern tree-ferns of the genus Angiopteris have, however, an analogous radiatingnbsp;structure.

The specimen is from the collection of Berlin H. Wright, Esq., of Penn Yan, New York, and was found in the Portage group (Uppernbsp;Erian) of Milo, New York, where it was associated with large petiolesnbsp;of ferns and trunks of Lepidodendra, probably L. Chemungeme andnbsp;L. primcBvum.

The occurrence of this and other stems of tree-ferns in marine beds has recently been illustrated by the observation of Prof. A.nbsp;Agassiz that considerable quantities of vegetable matter can benbsp;dredged from great depths in the sea on the leeward side of thenbsp;Caribbean Islands. The occurrence of these trunks further connectsnbsp;itself with the great abundance of large petioles (Rhachiopferis) innbsp;the same beds, while the rarity of well-preserved fronds is explainednbsp;by the coarseness of the beds, and also by the probably long maceration of the plant-remains in the sea-water.

In connection with this I may refer to the remarkable facts recently stated by Williamson¹ respecting the stems known as Ilete-rangium and Lyginodendron. It would seem that these, while having strong exogenous peculiarities, are really stems of tree-ferns, thusnbsp;placing this family in the same position of advancement with thenbsp;Lycopods and Zguisetaeem of the Coal period.

Large woody trunks, carbonised or silicifled, and showing wood-cells with hexagonal areoles having oval pores inscribed in them, occur abundantly in some beds of the Middle Erian of America, andnbsp;constitute the most common kind of fossil wood all the way to thenbsp;Trias. They have in the older formations, generally, several rowsnbsp;of pores on each fibre, and medullary rays composed of two or morenbsp;series of cells, but become more simple in these respects in the Permian and Triassic series. The names Arauearites and Araucarioxylon are perhaps objectionable, inasmuch as they suppose affinities tonbsp;Araucaria which may not exist. Unger�s name, which is non-

committal, is therefore, I think, to be preferred. In my � Acadian Greology,� and in my � Report on the Geology of Prince Edwardnbsp;Island,quot;� I have given reasons for believing that the foliage of somenbsp;at least of these trees was that known as Walchia, and that they maynbsp;have borne nutlets in the manner of �axine trees (Trigmiocarpum,nbsp;amp;o.). Grand d�Bury has recently suggested th.at some of them maynbsp;have belonged to Gordaites, or to plants included in that somewhatnbsp;varied and probably artificial group.

The earliest discovery of trees of this kind in the Brian of America was that of Matthew and Hartt, who found large trunks,nbsp;which I afterwards described as Dadoxylon Ouangondianum, in thenbsp;Brian sandstone of St. John, New Brunswick, hence named by thosenbsp;geologists the � Dadoxylon sandstone.� A little later, similar woodnbsp;was found by Prof. Hall and Prof. Newberry in the Hamilton groupnbsp;of New York and Ohio, and the allied wood of the genus Ormoxylonnbsp;was obtained by Prof. Hall in the Portage group of the formernbsp;State. These woods proved to be specifically distinct from that ofnbsp;St. John, and were named by me D. Halli, B. Newherryi, and Ormoxylon Erianum. The three species of Dadoxylon agreed in having composite medullary rays, and would thus belong to the groupnbsp;PaltBoxylon of Brongniart. In the case of Ormoxylon this characternbsp;could not be very distinctly ascertained, but the medullary raysnbsp;appeared to be simple.

I am indebted to Prof. J. M. Clarke, of Amherst College, Massachusetts, for some well-preserved specimens of another species from the Genesee shale of Canandaigua, New York. They show smallnbsp;stems or branches, with a cellular pith surrounded with wood ofnbsp;coniferous type, showing two to three rows of slit-formed, borderednbsp;pores in hexagonal borders. The medullary sheath consists ofnbsp;pseudo-scalariform and reticulated fibres; but the most remarkablenbsp;feature of this wood is the structure of the medullary rays, whichnbsp;are very frequent, but short and simple, sometimes having as fewnbsp;as four cells superimposed. This is a character not before observednbsp;in coniferous trees of so great age, and allies this Middle Briannbsp;form with some Carboniferous woods which have been supposed tonbsp;belong to Gordaites or Sigillaria. In any case this structure is new,nbsp;and I have named the species Dadoxylon Glarkii, after its discoverer.nbsp;The specimens occur, according to Prof. Clarke, in a calcareous layernbsp;which is filled with the minute shells of Styliola fissurella of Hall,nbsp;believed to be a Pteropod; and containing also shells of Qoniatitesnbsp;and Gyroeeras. The stems found are only a few inches in diameter,nbsp;but may be branches of larger trees.

Ib thus appears that we already know five species of Coniferous trees of the 'genus Dadoxylon in the Middle Brian of America, annbsp;interesting confirmation of the facts otherwise known as to thenbsp;great richness and variety of this ancient fiora. The late Prof.nbsp;Goeppert informed me that he had recognised similar wood in thenbsp;Devonian of Germany, and there can be no doubt that the fossilnbsp;wood discovered by Hugh Miller in the Old Bed Sandstone of Scotland, and described by Salter and MoNab, is of similar character, andnbsp;probably belongs to the genus Dadoxylon. Thus this type of Coniferous tree seems to have been as well established and differentiatednbsp;into species in the Middle Devonian as in the succeeding Carboniferous.

I may here refer to the fact that the lower limit of the trees of this group coincides, in America, with the upper limit of those problematical trees which in the previous chapter I have named Protogens {Nematophyton, Celluloxlyon¹ Nematoxylonf), though Apo-roxylon of Unger extends, in Thuringia, up to the Upper Devoniannbsp;(Cypridina schists).

Previously to the appearance of my descriptions of Devonian plants from North America, Hugh Miller had described forms fromnbsp;the Devonian of Scotland, similar to those for which I proposed thenbsp;generic name Psilophyton ; and I referred to these in this connectionnbsp;in my earliest description of that genus, He had also recognisednbsp;what seemed to be plants allied to Lycopods and Conifers. Mr.nbsp;Peach and Mr. Duncan had made additional disco veries of this kind,nbsp;and Sir J. Hooker and Mr. Salter had described some of these remains. More recently Messrs. Peach, Carruthers, and McNab havenbsp;worked in this field, and still later¹ Messrs. Jack and Etheridgenbsp;have summed up the facts and have added some that are new.

The first point to which I shall refer, and which will lead to the other matters to be discussed, is the relation of the characteristicnbsp;Lepidodendron of the Devonian of eastern America, L. Gaspianum,nbsp;to L. nofhum of Unger and of Salter. At the time when I describednbsp;this species I had not access to Scottish specimens of Lepidodendron

nbsp;nbsp;nbsp;�Journal of the Geological Society,� May, 1881.nbsp;f Ibid., vol. xix, 1863.

from the Devonian, but these had been well figured and described by Salter, and had been identified with L. notlium of Unger, a speciesnbsp;evidently distinct from mine, as was also that figured and describednbsp;by Salter, whether identical or not with Unger�s species. In 1870nbsp;1 had for the first time an opportunity to study Scottish specimensnbsp;in the collection of Mr. Peach; and on the evidence thus afforded Inbsp;stated confidently that these specimens represented a species distinctnbsp;from L. Oaspianum, perhaps even generically so.¹ It differs fromnbsp;L. Qaspianum in its habit of growth by developing small lateralnbsp;branches instead of bifurcating, and in its foliage by the absence ornbsp;obsolete character of the leaf-bases and the closely placed and somewhat appressed leaves. If an appearance of swelling at the end of anbsp;lateral branch in one specimen indicates a strobile of fructification,nbsp;then its fruit was not dissimilar from that of the Canadian speciesnbsp;in its position and general form, though it may have differed innbsp;details. On these grounds I declined to identify the Scottish speciesnbsp;with L. Gaspianum. The Lepidodendron from the Devonian ofnbsp;Belgium described and figured by Crepin,f has a better claim to suchnbsp;identification, and would seem to prove that this species existed innbsp;Europe as well as in America. I also saw in Mr. Peach�s collectionnbsp;in 1870 some fragments which seemed to me distinct from Salter�snbsp;species, and possibly belonging to L. Cfaspianum.X

In the earliest description of Psilophyton I recognised its probable generic affinity with Miller�s � dichotomous plants,� with Salter�s � rootlets,� and with Goeppert�s Haliaerites Dechenianus, and statednbsp;that I had � little doubt that materials exist in the Old Red Sandstone of Scotland for the reconstruction of at least one species ofnbsp;this genus.� Since, however. Miller�s plants had been referred tonbsp;coniferous roots, and to fucoids, and Goeppert�s Haliserites was anbsp;name applicable only to fucoids, and since the structure and fruitnbsp;of my plants placed them near to Lyoopods, I was under the necessity of giving them a special generic name, nor could I with certainty affirm their specific identity with any European species. Thenbsp;comparison of the Scottish specimens with woody rootlets, thoughnbsp;incorrect, is in one respect creditable to the acumen of Salter, as innbsp;almost any state of preservation an experienced eye can readily perceive that branchlets of Psilophyton must have been woody rather

f � Observations sur quelques Plantes Fossiles des d�p6ts Devoni-t �Proceedings of the Geological Society of London,� March, 1871.

than herbaceous, and their appearance is quite different from that of any true Algae.

The type of Psilophyton is my P. princeps, of which the whole of the parts and structures are well known, the entire plant beingnbsp;furnished in abundance and in situ in the rich plant-beds of Gasp�.nbsp;A second species, P. robustius, has also afforded well-characterisednbsp;fructification. P. elegans, whose fruit appears as � oval scales,� nonbsp;doubt bore sac-like spore-cases resembling those of the other species,nbsp;but in a different position, and perfectly flattened in the specimensnbsp;procured. The only other Canadian species, P. glahrum, being somewhat different in appearance from the others, and not having afforded any fructification, must be regarded as uncertain.

Stems dichotomous, with rudimentary subulate leaves, sometimes obsolete in terminal branohlets and fertile branches; and in decorticated specimens represented only by punctiform soars. Youngnbsp;branches cireinate. Khizomata cylindrical, with circular root-areoles. Internal structure of stem, an axis of scalariform vesselsnbsp;enclosed in a sheath of imperfect woody tissue and covered with anbsp;cellular bark more dense externally. Fruit, naked sac-like spore-cases, in pairs or clusters, terminal or lateral.

The Scottish specimens conform to these characters in so far as they are known, but not having as yet afforded fruit or internalnbsp;structure, they cannot be specifically determined with certainty.nbsp;More complete specimens should be carefully searched for, and willnbsp;no doubt be found.

In Belgium, M. Crepin has described a new species from the Upper Devonian of Condroz under the name P. Condrusianumnbsp;(1875). It wants, however, some of the more important characters ofnbsp;the genus, and differs in having a pinnate ramification, giving it thenbsp;aspect of a fern. In a later paper (1876) the author considers thisnbsp;species distinct from Psilophyton, and proposes for it a new genericnbsp;name Rhaeophyton.

The characters given by Mr. Carruthers, in his paper of 1873, for the species P. Bechenianum, are very few and general; �Lowernbsp;branches short and frequently branching, giving the plant an oblongnbsp;circumscription.� Yet even these characters do not apply, so far asnbsp;known, to Miller�s fucoids or Salter�s rootlets or Goeppert�s Halise-rites. They merely express the peculiar mode of branching alreadynbsp;referred to in Salter�s Lepidodendron nofhum. The identification ofnbsp;the former plants with the Lepidodendron and Lyeopodites, indeed,

rests only on mere Juxtaposition of fragments, and on the slight resemblance of the decorticated ends of the branches of the latter plants to Psilophyton. It is contradicted by the obtuse ends of thenbsp;branches of the Lepddodendron and Lycopodites, and by the apparently strobilaceous termination of some of them.

Salter�s description of his Lepidodendron nothum is quite definite, and accords with specimens placed in my hands by Mr. Peach: � Stems half an inch broad, tapering little, branches short; set on atnbsp;an acute angle, blunt at their terminations. Leaves in seven to tennbsp;rows, very short, not a line long, and rather spreading than closelynbsp;imbricate.� These characters, however, in so far as they go, arenbsp;rather those of the genus Lycopodites than of Lepidode7idron, fromnbsp;which this plant differs in wanting any distinct leaf-bases, and in itsnbsp;short, crowded leaves. It is to bo observed that they apply also tonbsp;Salter�s Lycopodites Milleri, and that the difference of the foliagenbsp;of that species may be a result merely of different state of preservation. For these reasons I am disposed to place these two supposed species together, and to retain for the species the namenbsp;Lycopodites Milleri. It may be characterised by the descriptionnbsp;above given, with merely the modification that the leaves are sometimes nearly one-third of an inch long and secund (Fig. 17, supra,nbsp;lower figure).

Decorticated branches of the above species may no doubt be mistaken for Psilophyton, but are nevertheless quite distinct from it, and the slender branching dichotomous stems, with terminations which,nbsp;as Miller graphically states, are � like the tendrils of a pea,� are toonbsp;characteristic to be easily mistaken, even when neither fruit nornbsp;leaves appear. With reference to fructification, the form of L.nbsp;Milleri renders it certain that it must have borne strobiles at thenbsp;ends of its branchlets, or some substitute for these, and not nakednbsp;spore-cases like those of Psilophyton.

The remarkable fragment communicated by Sir Philip Egerton to Mr. Carruthers,¹ belongs to a third group, and has, I think, been'nbsp;quite misunderstood. I am enabled to make this statement withnbsp;some confidence, from the fact that the reverse or counterpart of Sirnbsp;Philip�s specimen was in the collection of Sir Wyville Thomson, andnbsp;was placed by him in my hands in 1870. It was noticed in mynbsp;paper on � New Devonian Plants,� in the � Journal of the Geological Society of London,� and referred to my genus Ptilophyton, asnbsp;stated above under Section II., page 86 et seq.

Mr. Salter described, in 1857,¹ fragments of fossil wood from the Scottish Devonian, having the structure of Dadoxylon, though verynbsp;imperfectly preserved; and Prof. McNab has proposed f the genericnbsp;name Palmopitys for another specimen of coniferous wood collectednbsp;by Hugh Miller, and referred to by him in the � Testimony of thenbsp;Hocks.� From Prof. MoNab�s description, I should infer that thisnbsp;wood may, after all, be generically identical with the woods usuallynbsp;referred to Dadoxylon of Unger {Araucarioxylon of Kraus). Thenbsp;description, however, does not mention the number and dispositionnbsp;of the rows of pores, nor the structure of the medullary rays, and Inbsp;have not been able to obtain access to the specimens themselves. Inbsp;have described five species of Dadoxylon from the Middle and Upper Brian of America, all quite distinct from the Lower Carboniferous species. There is also one species of an allied genus, Ormoxylon.nbsp;All these have been carefully figured, and it is much to be desirednbsp;that the Scottish specimens should be re-examined and comparednbsp;with them.

Messrs. Jack and Etheridge have given an excellent summary of our present knowledge of the Devonian flora of Scotland, in thenbsp;Journal of the London Geological Society (1877). From this itnbsp;would appear that Species referable to the genera Calamites, Lepi-dodendron, Lycopodites, Psilophyton, ArtJirostigma, Archmopieris,nbsp;Gaulopteris, Palceopitys, Araucarioxylon, and Stigmaria have beennbsp;recognised.

The plants described by these gentlemen from the Old Bed Sandstone of Callender, I should suppose, from their figures andnbsp;descriptions, to belong to the genus Arthrostigma, rather than tonbsp;Psilophyton. I do not attach any importance to the suggestions referred to by them, that the apparent leaves may be leaf-bases. Longnbsp;leaf-bases, like those characteristic of Lepidofloyos, do not occur innbsp;these humbler plants of the Devonian. The stems with delicatenbsp;� horizontal processes � to which they refer may belong to Ptilophy-ton or to Pinnularia.

In conclusion, I need scarcely say that I do not share in the doubts expressed by some British pal�eontologists as to the distinctness of the Devonian and Carboniferous floras. In eastern America,nbsp;where these formations are mutually unconformable, there is, ofnbsp;course, less room for doubt than in Ireland and in western America, where they are stratigraphieally continuous. Still, in passing

� Journal of the London Geological Society.� f � Transactions of the Edinburgh Botanical Society,� 1870.

THE ERIAN OR DEVONIAN FORESTS.

from the one to the other, the species are for the most part different, and new generic forms are met with, and, as I have elsewhere shown, the physical conditions of the two periods were essentiallynbsp;different.¹

It is, however, to be observed that since�as Stur and others have shown�Calamitea radiatus, and other forms distinctively Devoniannbsp;in America, occur in Europe in the Lower Carboniferous, it is notnbsp;unlikely that the Devonian flora, like that of the Tertiary, appearednbsp;earlier in America. It is also probable, as I have shown in the � Reports � already referred to, that it appeared earlier in the Arctic thannbsp;in the temperate zone. Hence an Arctic or American flora, reallynbsp;Devonian, may readily be mistaken for Lower Carboniferous by anbsp;botanist basing his calculations on the fossils of temperate Europe.nbsp;Even in America itself, it would appear, from recent discoveries innbsp;Virginia and Ohio, that certain Devonian forms lingered longer innbsp;those regions than farther to the northeast; f and it would not benbsp;surprising if similar plants occurred in later beds in Devonshire ornbsp;in the south of Europe than in Scotland. Still, these facts, properlynbsp;understood, do not invalidate the evidence of fossil plants as tonbsp;geological age, though errors arising from the neglect of them arenbsp;still current.

VI.�Geological Relations op some Plant-beaeing Bebs of Eastern Canada. (� Report on Erian Plants,� 1871.)

The Gasp� sandstones have been fully described by Sir W. E. Logan, in his � Report on the Geology of Canada,� 1863. He therenbsp;assigns to them a thickness of seven thousand and thirty-six feet,nbsp;and shows that they rest conformably on the Upper Silurian limestones of the Lower Helderberg group (Ludlow), and are in theirnbsp;turn overlaid unconformably by the conglomerates which form thenbsp;base of the Carboniferous rooks of New Brunswick. I shall addnbsp;here merely a few remarks on points in their physical characternbsp;connected with the occurrence of plants in them.

Prototaxites {Nematophyton) Logani and other characteristic Lower Brian plants occur in the base of the sandstones at Littlenbsp;Gasp�. This fact, along with the occurrence, as stated in my papernbsp;of 1863, of rhizomes of Psilophyton preserving their scalariform

f Andrews, � Palieontology of Ohio,� vol. ii.; Meek, � Fossil Plants from Western Virginia,� Philosophical Society, Washington, 1876.

structure, in the upper part of the marine Upper Silurian limestone's,¹ proves the flora of the Devonian rocks to have had its beginning at least in the previous geological period, and to characterise the lower as well as the upper beds of the Devonian series. Innbsp;this connection I may state that, from their marine fossils, as wellnbsp;as their stratigraphical arrangement, Sir W. E. Logan and Mr.nbsp;Billings regard the lower portions of the Gasp� sandstones as thenbsp;equivalents of the Oriskany sandstone of New York. On the othernbsp;hand, the great thickness of this formation, the absence of Lowernbsp;Devonian fossils from its upper part, and the resemblance of thenbsp;upper beds to those of the newer members of the Devonian elsewhere, render it probable that the Gasp� sandstones, though deficient in the calcareous members of the system, seen farther to thenbsp;westward, represent the whole of the Devonian period.

The Gasp� sandstones, as their name imports, are predominantly arenaceous, and often coarsely so, the sandstones being frequentlynbsp;composed of large grains and studded with quartz-pebbles. Greynbsp;and buS are prevalent colours, but red beds also occur, more especially in the upper portion. There are also interstratifled shalynbsp;beds, sometimes occurring in groups of considerable thickness, andnbsp;associated with fine-grained and laminated argillaceous sandstone,nbsp;the whole having in many places the lithological aspect of the coal-measures. At one place, near the middle of the series, there is anbsp;bed of coal from one inch to three inches in thickness, associatednbsp;with highly bituminous shales abounding in remains of plants, andnbsp;also containing fragments of crustaceans and fishes {Pterygotus,nbsp;Ctenacanthus 9 amp;e.). The beds connected with this coal are greynbsp;sandstones and grey and dark shales, much resembling those of thenbsp;ordinary coal formation. The coal is shining and laminated, andnbsp;both its roof and floor consist of laminated bituminous shale withnbsp;fragments of Psilophyton. It has no true under-clay, and has been,nbsp;I believe, a peaty mass of rhizomes of Psilophyton. It occurs nearnbsp;Tar Point, on the south side of Gasp� Bay, a place so named fromnbsp;the occurrence of a thick dyke of trap holding petroleum in itsnbsp;cavities. The coal is of considerable horizontal extent, as in its linenbsp;of strike a similar bed has been discovered on the Douglas River,nbsp;about four miles distant. It has not been recognised on the north

The marine fossils of these beds have been determined by Mr. Billings. They are Upper Silurian, with an intermixture of Lower Devonian in the upper part. Fragments of Kematophyton occur in beds ofnbsp;the same age in the Bay des Chaleurs, at Cape Bon Ami.

side of the bay, though we find there beds, probably on very nearly the same horizon, holding Psilophyton in situ.

As an illustration of one of the groups of shaly beds, and of the occurrence of roots of Psilophyton, 1 may give the following sectional list of beds seen near � Watering Brook,� on the north shorenbsp;of the bay. The order is descending:

Groups of beds similar to the above, but frequently much more rich in fossils, occur in many parts of the section, and evidently include fossil soils of the nature of under-clays, on which little elsenbsp;appears to have grown than a dense herbage of Psilophyton, alongnbsp;with plants of the genus Arthrostigma.

In addition to these shaly groups, there are numerous examples of beds of shale of small thickness included in coarse sandstones,nbsp;and these beds often occur in detached fragments, as if the remnants of more continuous layers partially removed by currents ofnbsp;water. It is deserving of notice that nearly all these patches ofnbsp;shale are interlaced with roots or stems of Psilophyton, which sometimes project beyond their limits into the sandstone, as if the vegetable fibres had preserved the clay from removal. In short, thesenbsp;lines of patches of shale seem to be remnants of soils on whichnbsp;Psilophyton has flourished abundantly, and which have been partially swept away by the currents which deposited the sand. Somenbsp;of the smaller patches may even be fragments of tough swamp soilsnbsp;interwoven with roots, drifted by the agency of the waves or possiblynbsp;by ice; such masses are often moved in this way on the borders ofnbsp;modem swamps on the sea-coast.

The only remaining point connected with local geology to which I shall allude is the admirable facilities afforded by the Gasp� coastnbsp;both for ascertaining the true geological relations of the bods, andnbsp;for studying the Devonian plants, as distinctly exposed on large sur-

faces of rock. On the coast of the river St Lawrence, at Cape Rozier and its vicinity, the Lower Silurian rocks of the Quebecnbsp;group are well exposed, and are overlaid unconformably by the massive Upper Silurian limestones of Cape Gasp�, which rise into cliffsnbsp;six hundred feet in height, and can be seen filled with their characteristic fossils on both sides of the cape. Resting upon these, andnbsp;dipping at high angles toward Gasp� Bay, are the Devonian sandstones, which are exposed in rugged cliffs slightly oblique to theirnbsp;line of strike, along a coast-line of ten miles in length, to the headnbsp;of the bay. On the opposite side of the bay they reappear; and,nbsp;thrown into siight undulations by three anticlinal curves, occupynbsp;a line of coast fifteen miles in length. The perfect manner in whichnbsp;the plant-bearing beds are exposed in these fine natural sections maynbsp;serve to account for the completeness with which the forms andnbsp;habits of growth of the more abundant species can bo described.

In the Bay des Chaleurs, similar rocks exist with some local variations. In the vicinity of Campbellton are calcareous and magnesian breccia or agglomerate, hard shales, conglomerates and sandstones of Lower Devonian age. The agglomerate and lower shalesnbsp;contain abundant remains of fishes of the genera Cephalaspis, Coo-costeus, Ctenaeanthus, and Homacanthus, and also fragments ofnbsp;Fterygoius. The shales and sandstones abound in remains of Psilo-phyton, with which are Nematophyton, Arthroatigma, and Lepto-phleum of the same species found in the Lower Devonian of Gasp�nbsp;Bay. These beds near Campbellton dip to the northward, and thenbsp;Restigouche River here occupies a synclinal, for on the opposite side,nbsp;at Bordeaux Quarry, there are thick beds of grey sandstone dippingnbsp;to the southward, and containing large silicified trunks of Proto-taxites, in addition to PsilopTiyton. These beds are all undoubtedlynbsp;Lower Erian, but farther to the eastward, on the north side of thenbsp;river, there are newer and overlying strata. These are best seen atnbsp;Scaumenac Bay, opposite Dalhousie, between Cape Florissant andnbsp;Maguacha Point, where they consist of laminated and fine-grainednbsp;sandstone, with shales of grey colours, but holding some reddish bedsnbsp;at top, and overlaid unconformably by a great thickness of Lowernbsp;Carboniferous red conglomerate and sandstone. In these beds numerous fossil fishes have been found, among which Mr. Whiteavesnbsp;recognises species of Pterichthya, GlyptoUpis, Cheirolepis, amp;e. Withnbsp;these are found somewhat plentifully four species of fossil ferns, allnbsp;of Upper Erian types, of which one is peculiar to this locality; butnbsp;the others are found in the Upper Erian of Perry, in Maine, or innbsp;the Catskill group of New York.

In order that distinct notions may bo conyeyed as to the geological horizons of the species, I may state that the typical Devonian or Erian series of Canada and New York may be divided in descending order into�1. The Chemung group, including the Chemung andnbsp;Portage sandstones and shales. 3. The Hamilton group, includingnbsp;the Genesee, Hamilton, and Marcellus shales. 3. The Corniferousnbsp;limestone and its associated beds. 4. The Oriskany sandstone. Asnbsp;the Corniferous limestone, which is the equivalent of the Lowernbsp;Carboniferous limestone in the Carboniferous period, is marine, andnbsp;affords scarcely any plants, we may, as is usually done for like purposes in the Carboniferous, group it with the Oriskany under thenbsp;name Lower Erian. The Hamilton rocks will then be Middle Erian,nbsp;and the Chemung group Upper Erian. In the present state of ournbsp;knowledge, the series may be co-ordinated with the rocks of Gasp�,nbsp;New Brunswick, and Maine, as in the following table:

It may be proper, before closing this note, to state the reasons which have induced me to suggest in the following pages the use ofnbsp;the term � Ewan,� as equivalent to � Devonian,� for the great system of formations intervening between the Upper Silurian and thenbsp;Lower Carboniferous in America. 1 have been induced to adoptnbsp;this course by the following considerations; 1. The great area of

undisturbed and unaltered rocks of this age, including a thickness in some places of eighteen thousand feet, and extending from eastnbsp;to west through the Northern States of the Union and westernnbsp;Canada for nearly seven hundred miles, while it spreads from northnbsp;to south from the northern part of Michigan far into the Middlenbsp;States, is undoubtedly the most important Devonian area now knownnbsp;to geologists. 2. This area has been taken by all American geologists as their typical Devonian region. It is rich in fossils, andnbsp;these have been thoroughly studied and admirably illustrated bynbsp;the New York and Canadian Surveys. 3. The rocks of this areanbsp;surround the basin of Lake Erie, and were named, in the originalnbsp;reports of the New York Survey, the � Erie Division.� 4. Greatnbsp;difficulties have been experienced in the classification of the European Devonian, and the uncertainties thus arising have tended tonbsp;throw doubt on the results obtained in America in circumstances innbsp;which such difficulties do not occur.

These reasons are, I think, sufficient to warrant me in holding the great Erie Division of the New York geologists as the typicalnbsp;representative of the rocks deposited between the close of the Uppernbsp;Silurian and the beginning of the Carboniferous period, and to usenbsp;the term Brian as the designation of this great series of deposits asnbsp;developed in America, in so far at least as their flora is concerned.nbsp;In doing so, I do not wish to introduce a new name merely for thenbsp;sake of novelty ; but I hope to keep before the minds of geologistsnbsp;the caution that they should not measure the Brian formations ofnbsp;America, or the fossils which they contain, by the comparativelynbsp;depauperated representatives of this portion of the geological scalenbsp;in the Devonian of western Europe.

VII.�On the Relations of the so-called �Ursa Stage� of Bear Island with the Paleozoic Flora op Northnbsp;America.

The following note is a verbatim copy of that published by me in 1873, and the accuracy of which has now been vindicated by thenbsp;recent observations of Nathorst:

The plants catalogued by Dr. Heer, and characterising what he calls the � Ursa Stage,� are in part representatives of those of thenbsp;American flora which I have described as the � Lower Carboniferousnbsp;Coal-Measures � (Subcarboniferous of Dana), and whose characteristicnbsp;species, as developed in Nova Scotia, I noticed in the � Journal ofnbsp;the Geological Society � in 1858 (vol. xv.). Dr. Heer�s list, however,nbsp;includes some Upper Devonian forms; and I would suggest that

either the plants of two distinct beds, one Lower Carboniferous and the other Upper Devonian, have been near to or in contact with eachnbsp;other and have been intermixed, or else that in this high northernnbsp;latitude, in which (for reasons stated in my � Report on the Devonian Flora � ¹) I believe the Devonian plants to have originated, therenbsp;was an actual intermixture of the two floras. In America, at thenbsp;base of the Carboniferous of Ohio, a transition of this kind seemsnbsp;to occur; but elsewhere in northeastern America the Lower Carboniferous plants are usually unmixed with the Devonian.

Dr. Heer, however, proceeds to identify these plants with those of the American Chemung, and even with those of the Middle Devonian of New Brunswick, as described by me�a conclusion fromnbsp;which I must altogether dissent, inasmuch as the latter belong tonbsp;beds which were disturbed and partially metamorphosed before thenbsp;deposition of the lowest Carboniferous or � Suboarboniferous � beds.

Dr. Heer�s error seems to have arisen from want of acquaintance with the rich flora of the Middle Devonian, which, while differing innbsp;species, has much resemblance in its general facies, and especially innbsp;its richness in ferns, to that of the coal-formation.

To geologists acquainted with the stratigraphy and the accompanying animal fossils. Dr. Heer�s conclusions will of course appear untenable; but they may regard them as invalidating the evidencenbsp;of fossil plants; and for this reason it is, I think, desirable to givenbsp;publicity to the above statements.

I consider the British equivalent of the lower coal-measures of eastern America to be the lower limestone shales, the Tweediannbsp;group of Mr. Tate (1858), but which have sometimes been called thenbsp;� Calciferous Sandstone � (a name preoccupied for a Cambrian groupnbsp;in America). This group does not constitute � beds of passage � tonbsp;the Devonian, more especially in eastern America, where the lowernbsp;coal-formation rests unconformably on the Devonian, and is broadlynbsp;distinguished by its fossils.

The above notes would not have been extended to so great length, but for the importance of the Brian flora as the precursornbsp;of that of the Carboniferous, and the small amount of attentionnbsp;hitherto given to it by geologists and botanists.

Ascending from the Brian to the Carhoniferous system, so called because it contains the greatest deposits of anthracite and bituminous coal, we are still within thenbsp;limits of the Paleozoic period. We are still within thenbsp;reign of the gigantic cluh-mosses, cordaites, and taxinenbsp;pines. At the close of the Brian there had been oxernbsp;the whole northern hemisphere great changes of level,nbsp;accompanied by active volcanic phenomena, and undernbsp;these influences the land flora seems to have much diminished. At length all the old Brian species had becomenbsp;extinct, and their place was supplied by a meagre groupnbsp;of lycopods, ferns, and pines of different species fromnbsp;those of the preceding Brian. This is the flora of thenbsp;Lower Carboniferous series, the Tweedian of England,nbsp;the Horton series of Hova Scotia, the lower coal-measures of Virginia, the culm of Germany. But the landnbsp;again subsided, and the period of the marine limestonenbsp;of the Lower Carboniferous was introduced. In this thenbsp;older flora disappeared, and when the land emerged wenbsp;find it covered with the rich flora of the coal-formationnbsp;proper, in which the great tribes of the lycopods andnbsp;cordaites attained their maxima, and the ferns were continued as before, though under new generic and specificnbsp;forms.

There is something very striking in this succession of a new plant world without any material advance. It isnbsp;like passing in the modern world from one district tonbsp;another, in which we see the same forms of life, onlynbsp;represented by distinct though allied species. Thus, whennbsp;the voyager crosses the Atlantic from Europe to America, he meets with pines,nbsp;oaks, birches, poplars,nbsp;and beeches of the samenbsp;genera with those henbsp;had left behind ; butnbsp;the species are distinct.

It is something like this that meets us in our ascent into the Carboniferous world of plants.

Yet we know that this is a succession in time,nbsp;that all our old Eriannbsp;friends are dead andnbsp;buried long ago, andnbsp;that these are new formsnbsp;lately introduced (Fig.

Conveying ourselves, then, in imagination forward to the time whennbsp;our greatest accumula-

place to vast swampy flats, and which, instead of the oilbearing shales of the Erian, were destined to produce those immense and wide-spread accumulations of vegetable matter which constitute our present beds of bituminous and anthracite coal. Thenbsp;atmosphere of these great swampsnbsp;is moist and warm. Their vegetation is most exuberant, but ofnbsp;forms unfamiliar to modern eyes,nbsp;and they swarm with insects,nbsp;millepedes, and scorpions, andnbsp;with batrachian reptiles largenbsp;and small, among which we looknbsp;in vain for representatives of thenbsp;birds and beasts of the presentnbsp;day.

Prominent among the more gigantic trees of these swampynbsp;forests are those known to us asnbsp;Sigillarim (Fig. 33). They havenbsp;tall, pillar-like trunks, often several feet in diameter, ribbed likenbsp;fluted columns, but in the reverse way, and spreading at thenbsp;top into a few thick branches,nbsp;which are clothed with long,nbsp;grass-like leaves. They resemble in some respects the Lepi-dodendra of the Erian age, butnbsp;are more massive, with ribbed instead of scaly trunks, and longernbsp;leaves. If we approach one ofnbsp;them more closely, we are struck with the regular ribs ofnbsp;its trunk, dotted with rows of scars of fallen leaves, fromnbsp;which it receives its name Sigillaria, or seal-tree (Figs.nbsp;34-37). If we cut into its stem, we find that, instead of

the thin bark and firm wood with which we are familiar in our modern trees, it has a hard external rind, then anbsp;great thickness of cellular matter with rope-like bands ofnbsp;fibres, constituting an inner bark, while in the centre isnbsp;a firm, woody axis of comparatively small diameter, and

somewhat intermediate in its structures between that of the Lepidodendra and those of the cycads and the taxinenbsp;conifers. Thus a great stem, five feet in diameter, maynbsp;consist principally of cellular and bast fibres with verynbsp;little true woody matter. The roots of this tree are

perhaps its most singular feature. They usually start from the stem in four main branches, then regularlynbsp;bifurcate several times, and then run out into great

cylindrical cables, running for a long distance, and evidently intended to anchor the plant firmly in a soft and oozy soil. They were furnishednbsp;with long, cylindrical rootletsnbsp;placed regularly in a spiral manner, and so articulated that whennbsp;they dropped off they left regular rounded scars. They are,nbsp;in short, the Stigmariw, whichnbsp;we have already met with innbsp;the Brian (Figs. 38, 39). Innbsp;Fig. 33 I have endeavoured tonbsp;restore these strange trees. It isnbsp;not wonderful that such plantsnbsp;have caused much botanical con-Fio. 37.�Portion of lower troversy. It was long before bot-

their roots are properly roots at all, and not stems of some aquatic plant. Then the structure of their

stems is most puzzling, and their fruit is an enigma, for while some have found connected with them conesnbsp;supposed to resemble those ofnbsp;lycopods, others attribute tonbsp;them fruits like those of yew-trees. For years I have beennbsp;myself gathering materials fromnbsp;the rich coal-formation depositsnbsp;of Nova Scotia in aid of thenbsp;solution of these questions, andnbsp;in the mean time Dr. Williamson, of Manchester, and Renaultnbsp;and other botanists in France,nbsp;have been amassing and studying stores of specimens, and itnbsp;is still uncertain who may final-iy be the fortunate discoverernbsp;to set all controversies at rest,nbsp;that the true solution consists in the fact that there arenbsp;many kinds of Sigillarim, While in the modern forests

of America and Europe the species of any of our ordinary trees, as oaks, birches, or maples, may almost be countednbsp;on one�s fingers, Schimper in his yegetablo palaeontologynbsp;enumerates about eighty species of Carboniferous Sigil-laricB ; and while on the one hand many of these are sonbsp;imperfectly known that they may be regarded as uncertain, on the other hand many species must yet remain tonbsp;be discovered.¹ Now, in so vast a number of speciesnbsp;there must be a great range of organisation, and, indeed,nbsp;it has already been attempted to subdivide them intonbsp;several generic groups. The present state of the questionnbsp;appears to me to be this, that in these Sigillarim we havenbsp;a group divisible into several forms, some of which willnbsp;eventually be classed with the Lepidodendra as lycopods,nbsp;while others will be found to be naked-seeded phaeno-gams, allied to the pines and cycads, and to a remarkablenbsp;group of trees known as Cordaites, which we must shortlynbsp;notice.

Before considering other forms of Carboniferous vegetation, let us glance at the accumulation of coal, and the agency of the forests of Sigillarim therein. Let us imagine, in the first instance, such trees as those representednbsp;in the figures, growing thickly together over vast swampynbsp;flats, with quantities of undergrowth of ferns and othernbsp;plants beneath their shade, and accumulating from age tonbsp;age in a moist soil and climate a vast thickness of vegetable mould and trunks of trees, and spores and spore-cases, and we have the conditions necessary for the growthnbsp;of coal. Many years ago it was observed by Sir Williamnbsp;Logan that in the coal-field of South Wales it was thenbsp;rule with rare exceptions that, under every bed of coal,nbsp;there is a bed of elay filled with roots of the Stigmaria,nbsp;already referred to as the root of Sigillaria. This dis-

In a recent memoir (Berlin, 1887) Stur has raised the number of species in one subdivision of the SigillaHce (the Favularice) to forty-seven I

covery has since been extended to all the coal-fields of Europe and America, and it is a perfectly conclusive factnbsp;as regards the origin of coal. Each of these �underclays,� as they are called, must, in fact, have heen a soilnbsp;on which grew, in the first instance, Sigillarife and othernbsp;trees having stigmaria-roots. Thus, the growth of anbsp;forest of SigillaricB was the first step toward the accumulation of a bed of coal. More than this, in some of thenbsp;coarser and more impure coals, where there has beennbsp;sufficient earthy matter to separate and preserve impressions of vegetable forms, we can see that the mass of thenbsp;coal is made up of flattened SigillaricB, mixed with vege-

table debris of all kinds, including sometimes vast quantities of lepidodendroid spores, and the microscopic study of the coal gives similar results (Fig. 40). Further, onnbsp;the surfaces of many coals, and penetrating the shales ornbsp;sandstones which form their roofs, we find erect stumpsnbsp;of sigillaria and other trees, showing that the accumulation of the coal terminated as it had begun, by a forest-growth. I introduce here a section of a few of the numerous beds of coal exposed in the cliffs of the Southnbsp;Joggins, in Nova Scotia, in illustration of these facts.nbsp;AVe can thus see how in the slowly subsiding areas of thenbsp;coal-swamps successive beds of coal were accumulated,nbsp;alternating with beds of sandstone and shale (Figs. 41,nbsp;42). For other details of this kind I must refer tonbsp;papers mentioned in the sequel.

Eeturning to the more special subject of this work, I may remark that the lepidodendroid trees and the ferns,nbsp;both the arborescent and herbaceous kinds, are even morenbsp;richly represented in the Carboniferous than in the preceding Erian. I must, however, content myself withnbsp;merely introducing a few representatives of some of

the more common kinds, in an appended note, andnbsp;here give a figurenbsp;of a well-knownnbsp;Lower Carboniferous lepidodendron,nbsp;with its variousnbsp;forms of leaf-bases,nbsp;and its foliage andnbsp;fruit (Fig. 43), andnbsp;a similar illustration of an alliednbsp;generic form, thatnbsp;known as Lepido-phloios¹ (Fig. 44).

Another group which claims ournbsp;attention is thatnbsp;of the Calamites.nbsp;These are tall, cylindrical, branchless stems, withnbsp;whorls of branch-lets, bearing needlelike leaves and spreading in stools from the base, so as tonbsp;form dense thickets, like Southern cane-brakes (Fig. 46).nbsp;They bear, in habit of growth and fructification, a close

relation to our modern eqnisetums, or mare�s-tails, but, as in other cases -we have met with, are of gigantic sizenbsp;and comparatively complex structure. Their stems, innbsp;cross-section, show radiating bundles of fibres,nbsp;like those of exogenousnbsp;woods, yet the whole plannbsp;of structure presents somenbsp;curious resemblances tonbsp;the stems of their humble successors, the modern mare�s-tails. It wouldnbsp;seem, from the mannernbsp;in which dense brakes ofnbsp;these Calamites have beennbsp;preserved in the coal-formation of I^ova Scotia,nbsp;that they spread over lownbsp;and occasionally inundated flats, and formednbsp;fringes on the seawardnbsp;sides of the great Sigilla-ria forests. In this waynbsp;they no doubt contributed to prevent the invasion of the areas of coal accumulation by the muddy waters of inundations, andnbsp;thus, though they may not have furnished much of thenbsp;material of coal, they no doubt contributed to its purity.nbsp;Many beautiful plants of the genera AsteropJiyllites andnbsp;Annularia are supposed to have been allied to the Calamites, or to have connected them with the RMzocarps.nbsp;The stems and fruit of these plants have strong points ofnbsp;resemblance to those of Sphenophyllum, and the leavesnbsp;are broad, and not narrow and angular like those of thenbsp;true Catamites (Fig. 45).

THE CARBONIFEROUS FLORA.

son, of Manchester, to illustrate the structure of Cala-mites, and he has shown that these plants, like other cryptogams of the Carboniferous, had mostly stems withnbsp;regular fibrous wedges, like those of exogens. Thenbsp;structure of the stem is, indeed, so complex, and differsnbsp;so much in different stages of growth, and different statesnbsp;of preservation, that we are in danger of falling into thenbsp;greatest confusion in classifying these plants. Sometimesnbsp;what we call a Oalamite is a mere cast of its pith showingnbsp;longitudinal striae and constrictions at the nodes. Some-

times we have the form of the outer surface of the woody cylinder, showing longitudinal ribs, nodes, and marks ofnbsp;the emission of the branchlets. Sometimes we have thenbsp;outer surface of the plant covered with a smooth barknbsp;showing flat ribs, or almost smooth, and having at thenbsp;nodes regular articulations with the bases of the verticil-

late branchlets, or on the lower part of the stem the marks of the attachment of the roots. The Catamitesnbsp;grew in dense clumps, budding off from one another,nbsp;sometimes at different lerels, as the mud or sand accumulated about their stems, and in somenbsp;species there were creeping rhizomatanbsp;or root-stocks (Figs. 46 to 49).

Dr. Williamson describes three distinct structural types. What he regards as typical Calamites has in its woodynbsp;zone wedges of barred vessels, with thick bands of cellular tissue separating them. A second type, which

he refers to Calamopitus, has woody bundles composed of reticulated or multiporous fibres, with their porous sides parallel to the medullary rays, which arenbsp;better developed than in the previous form. The intervening cellular masses are composed of elongated cells.nbsp;This is a decided advance in structure, and is of the tyjienbsp;of those forms having the most woody and largest stems.

f9T�r�r�i

which Brongniart named Calamodendron (Big. 50). A third form, to which Dr. Williamson seems to prefer tonbsp;assign this last name, has the tissue of the woody wedgesnbsp;barred, as in the first, but the medullary rays are betternbsp;developed than in the second. In this third form thenbsp;intermediate tissue, or primary medirllary rays, is trulynbsp;fibrous, and with secondary medullary rays traversing it.nbsp;My own observations lead me to infer that there was anbsp;fourth type of calamitean stem, less endowed with woodynbsp;matter, and having a larger fistulous or cellular cavitynbsp;than any of those described by Dr. Williamson.

and complicated stems belonged to higher and nobler types of mare�s-tails than those of the modern world, andnbsp;that their fructification was equisetaceous and of thenbsp;form known as Calamostachys.

We have already seen that noble tree-ferns existed in the Brian period, and these were continued, and theirnbsp;number and variety greatly extended, in the Carboniferous. In regard to the structure of their stems, and thenbsp;method of supporting these by aerial roots, the tree-fernsnbsp;of all ages have been nearly alike, and the form andnbsp;structure of the leaves, except in some comparatively rarenbsp;and exceptional types, has also been much the same.nbsp;Any ordinary observer examining a collection of coal-formation ferns recognises at once their kinship to thenbsp;familiar brackens of our own time. Their fructificationnbsp;is, unfortunately, rarely preserved, so that we are notnbsp;able, in the case of many species, to speak confidently of

their affinities with modern forms ; but the knowledge of this subject has been constantly extending, and a sufficient amount of information has been obtained to enablenbsp;us to say something as to their probable relationships.nbsp;(Figs. 51 to 55.)

The families into which modern ferns are divided are, it must be confessed, somewhat artificial, and in the case

of fossil ferns, in which the fructification is for the most part wanting, it is still more so, depending in great partnbsp;on the form and venation of the divisions of the fronds.

Of about eight families into which modern ferns are divided, seven are found in a fossil state, and of these,nbsp;four at least, the Cyathacem, the Ophioglossem, the Hy-

THE CARBONIFEROUS FLORA.

Some of these ferns have the more complex kind of spore-case, with a jointed, elastic ring. It is to be oh-

served, however, that those forms which have a simple spore-case, either netted or membranous, and withoutnbsp;annulus, are most common in the Devonian and lowest

Fig. 55.�Fructification of Palseozoic ferns, a, Thecae of Archmopteris (Erian). Theca of Senftenhergia (Carboniferous), Thee� ofnbsp;ABterotheca (Carboniferous).

Carboniferous. Some of the forms in these old rocks are somewhat difficult to place in the system. Of these, the

Mr. R. Kidston has recently described very interesting forma of fern fructification from the coal-formation of Great Britain, and muchnbsp;has been done by European palaeobotanists, and also by Lesquereux andnbsp;Fontaine in America.

Fiq. 56.�Tree-ferns of the Carboniferous, a, MegapTiyton magnificwn, Dawson, restored. B, Leaf-scar of the same, two thirds natural size.nbsp;E� Row of leaf-soars, reduced, o, Palaeopterla Hartii, scars half natural size. D, Palwopteris Acadica, soars half natural size.

species of Archmopteris, of the Upper and Middle Brian, are eminent as examples. This type, howerer, scarcelynbsp;extends as high as the coal-formation.¹ Some of thenbsp;tree-ferns of the Carboniferous present very remarkablenbsp;features. One of these, of the genus Megaphyton, seemsnbsp;to have two rows of great leaves, one at each side of thenbsp;stem, which was probably sustained by large bundles ofnbsp;aerial roots (Big. 56).

In the Carboniferous, as in the Brian, there are leaves which have been referred to ferns, but are subject tonbsp;doubt, as possibly belonging to broad-leaved taxine treesnbsp;allied to the gingko-tree of China. One of these, repre'-

sented in Big. 57, has been found in the coal-formation ofnbsp;Uova Scotia, and referred to thenbsp;doubtful genus NoeggeratJiia.nbsp;Bontaine has proposed for similar leaves found in Virginia thenbsp;new generic name Saportea.

Berns, as might he inferred from their great age, are at thenbsp;present time dispersed over thenbsp;whole world; but their headquarters, and the regions tonbsp;which tree-ferns are confined,nbsp;are the. more moist climates of the tropics and of thenbsp;southern hemisphere. The coal-swamps of the northernnbsp;hemisphere seem to have excelled even these favourednbsp;regions of the present world as a paradise for ferns.

I have already stated that the Carboniferous constitutes the headquarters of the Gordaites (Big. 58), of which a large number of species have been described, both in

The pretty little ferns of the genus Botrydiium (moonwort), so common in American and European woods, seem to be their nearest mod�nbsp;ern allies.

Europe and America. We sometimes, though rarely, find their stems showing structure. In this case we havenbsp;a large cellular pith, often divided by horizontal partitions into flat chambers, and constituting the objectsnbsp;which, when detached, are called Sternbergim (Eig. 62).nbsp;These Sternbergia piths, however, occur in true conifers as well, as they donbsp;in the modern worldnbsp;in some trees, like oiirnbsp;common butternut, ofnbsp;higher type ; and Inbsp;showed many years agonbsp;that the Sternbergianbsp;type may be detectednbsp;in the young twigs ofnbsp;the balsam-fir [Abiesnbsp;balsamifera). The pithnbsp;was surrounded by anbsp;ring of scalariform ornbsp;barred tissue, often ofnbsp;considerable thickness,nbsp;and in young stems sonbsp;important as to havenbsp;suggested lycopodia-ceous affinities. But asnbsp;the stem grew in size,nbsp;a regular ring of woodynbsp;wedges, with tissue having rounded or hexagonal pores or discs,nbsp;like those of pines, was developed. Outside this was anbsp;bark, often apparently of some thickness. This structure in many important points resembles that of cycads,nbsp;and also approaches to the structure of Sigillaria, whilenbsp;in its more highly developed forms it approximates tonbsp;that of the conifers.

On the stems so constructed were placed long and often broad many-nerved leaves, with rows of stomata ornbsp;breathing-pores, and attached by somewhat broad basesnbsp;to the stem and branches. The fruit consisted of racemes,nbsp;or clusters of nutlets, which seem to have been provided

with, broad lateral wings for flotation in the air, or in some cases with a pnlpy envelope, which flattens into anbsp;film. There seem to have been structures of both thesenbsp;kinds, though in the state of preservation of these curiousnbsp;seeds it is extremely difficult to distinguish them. In thenbsp;first case they must have been intended for disseminationnbsp;by the wind, like the seeds of spruces. In the latter casenbsp;they may have been disseminated like the fruits of taxinenbsp;trees by the agency of animals, though what these werenbsp;it would be difficult to guess. These trees had very greatnbsp;reproductive power, since they produced numerous seeds,nbsp;not singly or a few together, as in modern yews, but innbsp;long spikes or catkins bearing many seeds (Pig. 59).

It is to be observed that the Oordaites, or the Cor-daitinm, as they have been called, as a family,¹ constitute another of those intermediate groups with which we havenbsp;already become familiar. On the one hand they approachnbsp;closely to the broader-leaved yews like Gingko, Phyllo-cladus, and Podocarpus, and, on the other hand, theynbsp;have affinities with Oyoadacese, and even with Sigillarise.nbsp;They were beautiful and symmetrical trees, adding something to the variety of the rather monotonous Paleozoic forests. They contributed also somewhat to the accumulation of coal. I have found that some thin beds arenbsp;almost entirely composed of their leaves, and the tissuesnbsp;of their wood are not infrequent in the mineral charcoalnbsp;of the larger coal-seams. There is no evidence that theirnbsp;roots were of the stigmaroid type, though they evidentlynbsp;grew in the same swampy flats with the Sigillarise andnbsp;Galamites.

It may, perhaps, be well to say here that I believe there was a considerably wide range of organisation in thenbsp;Oordaitinse as well as in the Galamites and Sigillarim, andnbsp;that it will eventually be found that there were three lines

of connection between the higher cryptogams and the phaenogams, one leading from the lycopods by the Sigil-lariae, another leading by the Cordaites, and the thirdnbsp;leading from the Equisetums by the Calami tes. Stillnbsp;further back the characters afterward separated in thenbsp;club-mosses, mare�s-tails, and ferns, were united in thenbsp;Ehizocarps, or, as some now, but I think somewhat unreasonably, prefer to call them, the � heterosporous Eili-cinse.� In the more modern world, all the connectingnbsp;links have become extinct and the phsenogams standnbsp;widely separated from the higher cryptogams. I do notnbsp;make these remarks in a Darwinian sense, but merely tonbsp;state what appear to be the lines of natural affinity andnbsp;the links wanting to give unity to the system of nature.

Of all the trees of the modern world, none are perhaps so widely distributed as the pines and their allies. Onnbsp;mountain-tops and within the Arctic zone, the last treesnbsp;that can struggle against the unfavourable conditions ofnbsp;existence are the spruces and firs, and in the warm andnbsp;moist islands of the tropics they seem equally at homenbsp;with the tree-ferns and the palms. We have already seennbsp;that they are a very ancient family, and in the sandstonesnbsp;of the coal-formation their great trunks are frequentlynbsp;found, infiltrated with calcareous or silicious matter, andnbsp;still retaining their structure in the greatest perfectionnbsp;(Pig. 60). So far as we know, the foliage of some of themnbsp;which constitutes the genera WalcMa and Araucarites ofnbsp;some authors (Pigs. 60, 63) was not dissimilar from thatnbsp;of modern yews and spruces, though there is reason tonbsp;believe that some others had broad, fern-like leaves likenbsp;those of the gingko. Hone of them, so far as yet certainly known, were cone-bearing trees, their fruit havingnbsp;probably been similar to that of the yews (Fig. 61).nbsp;The minute structures of their stems are nearer to thosenbsp;of the conifers of the islands of the southern hemispherenbsp;than to that of those in our northern climes�a cor-

relation, no doubt, to the equable climate of the period. There is not much evidence that they grew with the Si-gillarim in the true coal-swamps, though some specimensnbsp;have been found in this association. It is more likelynbsp;that they were in the main inland and upland trees, and

that in conseqnence they are mostly known to us by drifted trunks borne by river inundations into the seasnbsp;and estuaries.

A remarkable fact in connection with them, and showing also the manner in which the most durable vegetable structures may perish by decay, is that, like the Cordaites,nbsp;they had large piths with transverse partitions, a struct-

ure which, as I have already mentioned, appears on a minute scale in the twigs of the fir-tree, and that sometimes casts of these piths in sandstone appear in a separatenbsp;form, constituting what have been named Sternbergice ornbsp;Artisim. As Eenault well remarks with reference tonbsp;Cordaites, the existence of this chambered form of pithnbsp;implies rapid elongation of the stem, so that the Cordaitesnbsp;and conifers of the coal-formation were probably quicklynbsp;growing trees (Eig. 62).

The same general statements may be made as to the coal-vegetation as in relation to that of the Brian. In

the coal period we have found none of the higher exogens, and there are only obscure and uncertain indications of the presence of endogens, which we may reserve for a future chapter ; but gymnosperms abound and arenbsp;highly characteristic. On the other hand, we have nonbsp;mosses or lichens, and very few Algae, but a great number of ferns and Lycopodiaceae or club-mosses (Big. 63).nbsp;Thus, the coal-formation period is botanically a meeting-place of the lower phfflnogams and the higher cryptogams,nbsp;and presents many forms whicli, when imperfectly known,nbsp;have puzzled botanists in regard to their position in onenbsp;or other series. In the present world, the flora most akin

to that of the coal period is that of warm, temperate regions in the southern hemisphere. It is not properly a tropical flora, nor is it the flora of a cold region, hutnbsp;rather indicative of a moist and equable climate. Still,

we must bear in mind that we may often be mistaken in reasoning as to the temperature required by extinctnbsp;species of plants, differing from those now in existence.nbsp;Further, we must not assume that the climatal conditionsnbsp;of the northern hemisphere were in the coal period at allnbsp;similar to those which now prevail. As Sir Charles Lyellnbsp;has shown, a less amount of land in the higher latitudesnbsp;would greatly modify climates, and there is every reasonnbsp;to believe that in the coal period there was less land thannbsp;now. Further, it has been shown by Tyndall that a verynbsp;small additional amount of carbonic acid in the atmosphere would, by obstructing the radiation of heat fromnbsp;the earth, produce almost the effect of a glass roof or conservatory, extending over the whole world. Again, therenbsp;is much in the structure of the leaves of the coal-plants,nbsp;as well as in the vast amount of carbon which they accumulated in the form of coal, and the characteristics ofnbsp;the animal life of the period, to indicate, on independent

grounds, that the carboniferous atmosphere differed from that of the present world in this way, or in the presencenbsp;of more carbonic acid�a substance now existing in thenbsp;very minute proportion of one thousandth of the whole�nbsp;a quantity adapted to the present requirements of vegetable and animal life, hut probably not to those of thenbsp;coal period.

Thus, if we inquire as to any analogous distribution of plants in the modern world, we find this only in the warmer insular climates of the southern hemisphere, wherenbsp;ferns, lycopods, and pines appear under forms somewhat akin to those of the Carboniferous, but mixed withnbsp;other types, some of which are modern, others allied tonbsp;those of the next succeeding geological ages of the Mesozoic and Tertiary; and under these periods it will benbsp;more convenient to make comparisons.

The readers of recent English popular works on geology will have observed the statement reiterated that a large proportion of the material of the great beds of bituminous coal is composed of the spore-cases of lycopo-diaceous plants�a statement quite contrary to that resulting from my microscopical examinations of the coalnbsp;of more than eighty coal-beds in Nova Scotia and Capenbsp;Breton, as stated in �Acadian Geology� (page 463), andnbsp;more fully in my memoir of 1858 on the � Structures innbsp;Coal,� ¹ and that of 1866, on the � Conditions of Accumulation of Coal.�f The reason of this mistake is,nbsp;that an eminent English naturalist, happening to find innbsp;certain specimens of English coal a great quantity of remains of spores and spore-cases, though even in his specimens they constitute only a small portion of the mass,nbsp;and being apparently unacquainted with what others hadnbsp;done in this field, wrote a popular article for the � Contemporary Review,� in which he extended an isolated and

exceptional fact to all coals, and placed tbis supposed origin of coal in a light so brilliant and attractive that henbsp;has been followed by many recent writers. The fact is,nbsp;as stated in � Acadian Geology,� that trunks of Sigillarimnbsp;and similar trees constitute a great part of the densernbsp;portion of the coal, and that the cortical tissues of thesenbsp;rather than the wood remain as coal. But cortical ornbsp;epidermal tissues in general, whether those of spore-casesnbsp;or other parts of plants, are those which from their resistance to water-soakage and to decay, and from theirnbsp;highly carbonaceous character, are best suited to the production of coal. In point of fact, spore-cases, thoughnbsp;often abundantly present, constitute only an infinitesimalnbsp;part of the matter of the great coal-beds. In an articlenbsp;in � The American Journal of Science,� which appearednbsp;shortly after that above referred to, I endeavoured to correct this error, though apparently without ei�ect in so farnbsp;as the majority of British -geological writers are concerned. From this -article I have taken -with little changenbsp;the following passages, as it is of importance in theoreticalnbsp;geology that such mistakes, involving as they do thenbsp;whole theory of coal accumulation, should not continuenbsp;to pass current. The early part of the paper is occupiednbsp;with facts.as to the occurrence of spores and spore-cases asnbsp;partial ingredients in coaL Its conclusions,are as follows :

It is not improbable that sporangites, or bodies resembling them, may be found in most coals ; but it is most likely that their -occurrence is accidental rathernbsp;than essential to coal accumulation, and that they arenbsp;more likely to have been .abundant in shales and cannelnbsp;coals, deposited in ponds or in shallow waters in the vicinity of lycopodiaceous forests, than in the swampynbsp;or peaty deposits which constitute the ordinary coals.nbsp;It is to be observed, however, that the conspicuous appearance which these bodies, and also the strips andnbsp;fragments of epidermal tissue, which resemble them in

texture, present in slices of coal, may incline an observer, not having large experience in the examination of coals,nbsp;to overrate their importance ; and this I think has beennbsp;done by most microscopists, especially those who havenbsp;confined their attention to slices prepared by the lapidary.nbsp;One must also bear in mind the danger arising from mistaking concretionary accumulations of bituminous matternbsp;for sporangia. In sections of the bituminous shales accompanying the Devonian coal above mentioned, therenbsp;are many rounded yellow spots, which on examinationnbsp;prove to be the spaces in the epidermis of PsilopJiytonnbsp;through which the vessels passing to the leaves werenbsp;emitted. To these considerations I would add the following, condensed from the paper above referred tonbsp;(p. 139), in which the whole question of the origin ofnbsp;coal is fully discussed :¹

1. nbsp;nbsp;nbsp;The mineral charcoal or 'mother coal� is obviouslynbsp;woody tissue and fibres of bark, the structure of the varieties of which, and the plants to which it probably belongs, I have discussed in the paper above mentioned.

2. nbsp;nbsp;nbsp;The coarser layers of coal show under the microscope a confused mass of fragments of vegetable matternbsp;belonging to various descriptions of plants, and including, but not usually in large quantities, sporangites.

3. nbsp;nbsp;nbsp;The more brilliant layers of the coal are seen,nbsp;when separated by thin laminae of clay, to have on theirnbsp;surfaces the markings of Sigillarim and other trees, ofnbsp;which they evidently represent flattened specimens, ornbsp;rather the bark of such specimens. Under the microscope, when their structures are preserved, these layersnbsp;show cortical tissues more abundantly than any others.

4. nbsp;nbsp;nbsp;Some thin layers of coal consist mainly of flattened layers of leaves of Cordaites or Pychnopliyllum.

Sigillaria in the coal-roofs equally testify to the accumulation of coal by the growth of successive forests, more especially of Sigillarm. There is, on the other hand, nonbsp;necessary connection of sporangite-beds with Stigmariannbsp;soils. Such beds are more likely to be accumulated innbsp;water, and consequently to constitute bituminous shalesnbsp;and cannels.

6. Lepidodendron and its allies, to which the spore-cases in question appear to belong, are evidently much less important to coal accumulation than Sigillaria, whichnbsp;cannot be affirmed to have produced spore-cases similarnbsp;to those in question, even though the observation ofnbsp;Groldenberg as to their fruit can be relied on ; the accuracy of which, however, I am inclined to doubt.

On the whole, then, while giving due credit to those who have advocated the spore-theory of coal, for directingnbsp;attention to this curious and no doubt important constituent of mineral fuel, and admitting that I may possiblynbsp;have given too little attention to it, I must maintain thatnbsp;sporangite-beds are exceptional among coals, and thatnbsp;cortical and woody matters are the most abundant ingredients in all the ordinary kinds; and to this I cannotnbsp;think that the coals of England constitute an exception.

It is to be observed, in conclusion, that the spore-cases of plants, in their indestructibility and richly carbonaceous character, only partake of qualities common to most suberous and epidermal matters, as I have explainednbsp;in the publications already referred to. Such ejDidermalnbsp;and cortical substances are extremely rich in carbon andnbsp;hydrogen, in this resembling bituminous coal. They arenbsp;also very little liable to decay, and they resist more thannbsp;other vegetable matters aqueous infiltration�propertiesnbsp;which have caused them to remain unchanged, and tonbsp;continue free from mineral additions more than othernbsp;vegetable tissues. These qualities are well seen in thenbsp;bark of our American white birch. It is no wonder that

materials of this kind should constitute considerable portions of such Tegetable accumulations as the beds ofnbsp;coal, and that when present in large proportion theynbsp;should afford richly bituminous beds. All this agreesnbsp;with the fact, apparent on examination of the commonnbsp;coal, that the greater number of its purest layers consistnbsp;of the flattened bark of Sigillarim and similar trees. Justnbsp;as any single flattened trunk embedded in shale becomesnbsp;a layer of pure coal. It also agrees with the fact thatnbsp;other layers of coal, and also the cannels and earthynbsp;bitumens, appear under the microscope to consist ofnbsp;finely comminuted particles, principally of epidermal tissues, not only from the fruits and spore-cases of plants,nbsp;but also from their leaves and stems. These considerations impress us. Just as much as the abundance of spore-cases, with the immense amount of the vegetable matternbsp;which has perished during the accumulation of coal, innbsp;comparison with that which has been preserved.

I am indebted to Dr. T. Sterry Hunt for the following very valuable information, which at once places in a clear and precise light the chemical relations ofnbsp;epidermal tissue and spores with coal. Dr. Hunt says :nbsp;�The outer bark of the cork-tree, and the cuticle ofnbsp;many if not all other plants, consists of a highly carbonaceous matter, to which the name of suierin has beennbsp;given. The spores of Lycopodium also approach to thisnbsp;substance in composition, as will be seen by the following, one of two analyses by Duconi,* along with whichnbsp;I give the theoretical composition of pure cellulose ornbsp;woody fibre, according to Payen and Mitseherlich, andnbsp;an analysis of the suberin of cork, from Quercus suier,nbsp;from which the ash and 3'5 per cent of cellulose havenbsp;been deducted, f

*� Liebig and Kopp, � Jaliresbuch,� ] 847-�48. f Gmelin, � Handbook,� xv., 146.

�This difference is not less striking when we reduce the above centesimal analyses to correspond with thenbsp;formula of cellulose, O24H20O20, and represent cork andnbsp;Lycopodium as containing twenty-four equivalents ofnbsp;carbon. For comparison I give the composition of specimens of peat, brown coal, lignite, and bituminous coal :¹

�It will be seen from this comparison that, in ultimate composition, cork and Lycopodium are nearer to lignite than to woody fibre, and may be converted intonbsp;coal with far less loss of carbon and hydrogen than thenbsp;latter. They in fact approach closer in composition tonbsp;resins and fats than to wood, and, moreover, like thosenbsp;substances repel water, with which they are not easilynbsp;moistened, and thus are able to resist those atmosphericnbsp;influences which effect the decay of woody tissue.�

I would add to this only one further consideration. The nitrogen present in the Lycopodium spores, no doubt,nbsp;belongs to the protoplasm contained in them, a substancenbsp;which would soon perish by decay; and subtracting this,nbsp;the cell-walls of the spores and the walls of the spore-

cases would be most suitable material for the production of bituminous coal. But this suitableness they share withnbsp;the epidermal tissue of the scales of strobiles, and of thenbsp;stems and leaves of ferns and lycopods, and, above all,nbsp;with the thick, corky envelope of the stems of Sigillarimnbsp;and similar trees, which, as I have elsewhere shown,¹nbsp;from its condition in the prostrate and erect trunks contained in the beds associated with coal, must have beennbsp;highly carbonaceous and extremely enduring and impermeable to water. In short, if, instead of � spore-cases,�nbsp;we read �epidermal tissues in general, including spore-cases,� all that has been affirmed regarding the latter willnbsp;be strictly and literally true, and in accordance with thenbsp;chemical composition, microscopical characters, and modenbsp;of occurrence of coal. It will also be in accordance withnbsp;the following statement, from my paper on the �Structures in Coal,� published in 1859 :

� A single trunk of Sigillaria in an erect forest presents an epitome of a coal-seam. Its roots represent the Stigmaria underclay; its bark the compact coal; itsnbsp;woody axis the mineral charcoal; its fallen leaves (andnbsp;fruits), with remains of herbaceous plants growing in itsnbsp;shade, mixed with a little earthy matter, the layers ofnbsp;coarse coal. The condition of the durable outer bark ofnbsp;erect trees concurs with the chemical theory of coal, innbsp;showing the especial suitableness of this kind of tissue fornbsp;the production of the purer compact coals. It is alsonbsp;probable that the comparative impermeability of the barknbsp;to mineral infiltration is of importance in this respect,nbsp;enabling this material to remain unaffected by causesnbsp;which have filled those layers, consisting of herbaceousnbsp;materials and decayed wood, with pyrites and other mineral substances.�

�Vegetable Structures in Coal,� �Journal of Geological Society,� XV., 626. � Conditions of Accumulation of Coal,� ibid., xxii., 95. �Acadian Geology,� igY, 464.

We need not go far in search of the uses of the coal vegetation, when we consider the fact that the greatestnbsp;civilised nations are dependent on it for their fuel. Without the coal of the Carboniferous period and the iron-orenbsp;which is one of the secondary consequences of coal accumulation, just as bog-ores of iron occur in the subsoilsnbsp;of modern peats, it would have been impossible either tonbsp;sustain great nations in comfort in the colder climates ofnbsp;the northern hemisphere or to carry on our arts andnbsp;manufactures. The coal-formation yields to Great Brit-ian alone about one hundred and sixty million tons ofnbsp;coal annually, and the miners of the United States extract mainly from the same formation nearly a hundrednbsp;million tons, while the British colonies and dependencies produce about five million tons ; and it is a remarkable fact that it is to the English race that thenbsp;greatest supply of this buried power and heat and lightnbsp;has been given.

The great forests of the coal period, while purifying the atmosphere of its excess of unwholesome carbonicnbsp;acid, were storing up the light and heat of Palfflozoicnbsp;summers in a form in which they could be recovered in ournbsp;human age, so that, independently of their uses to thenbsp;animals which were their contemporaries, they are indispensable to the existence of civilised man.

Nor can we hope soon to be able to dispense with the services of this accumulated store of fuel. The forestsnbsp;of to-day are altogether insufBcient for the supply of ournbsp;wants, and though we are beginning to apply water-powernbsp;to the production of electricity, and though some promising plans have been devised for the utilisation of thenbsp;direct heat and light of the sun, we are still quite as dependent as any of our predecessors on what has been donenbsp;for us in the Paleozoic age.

In the previous pages I have said little respecting the physical geography of the Carboniferous age ; but, as may

be inferred from the vegetation, this in the northern hemisphere presented a greater expanse of swampy fiatsnbsp;little elevated above the sea than we find in any other period. As to the southern hemisphere, less is known, butnbsp;the conditions of vegetation would seem to have been essentially the same.

Taking the southern hemisphere as a whole, I have not seen any evidence of a Lower Devonian or Upper Silurian flora; but in South Africa and Australia there arenbsp;remains of Upper Devonian or Lower Carboniferousnbsp;plants. These were succeeded by a remarkable Uppernbsp;Carboniferous or Permian group, which spread itself allnbsp;over India, Australia, and South Africa,¹ and containsnbsp;some forms {Vertehraria, Phyllotheca, Glossopteris, amp;c.)nbsp;not found in rocks of similar age in the northern hemisphere, so that, if the age of these beds has been correctlynbsp;determined, the southern hemisphere was in advance innbsp;relation to some genera of plants. This, however, is tonbsp;be expected when we consider that the Triassic and Jurassic flora of the north contains or consists of intrudersnbsp;from more southern sites. These beds are succeeded innbsp;India by others holding cyeads, amp;c., of Upper Jurassicnbsp;or Lower Cretaceous types (Eajmahal and Jabalpurnbsp;groups).

Blanford has shown that there is a very great similarity in this series all over the Australian and Indian region, f Hartt and Darby have in like manner distinguished Devonian and Carboniferous forms in Brazil akin to those of the northern hemisphere. Thus the southernnbsp;hemisphere would seem to have kept pace with the northern, and according to Blanford there is evidence there ofnbsp;cold conditions in the Permian, separating the Palaeozoic

Wytey, � Journal Geol. Society,� vol. xxiii., p. 172; Daintree, ibid., �vol. xx'viii.; also Clarke and McCoy.

flora from that of the Mesozoic, in the same manner that Eamsay has supposed a similar period of cold to have donenbsp;north of the equator. This would imply a very greatnbsp;change of climate, since we have evidence of the extension of the Lower Carboniferous flora at least as farnbsp;north as Spitzbergen. The upper coal-formation wenbsp;cannot, however, trace nearly so far north; so that anbsp;gradual refrigeration may have been going on beforenbsp;the Permian. Thus in both hemispheres there was anbsp;general similarity in the later Palaeozoic flora, and perhaps similar conditions leading to its extinction and tonbsp;its replacement by that to be described in the nextnbsp;chapter.

In the space available in this work it would be impossible to enter fully into the classification of Palaeozoic plants; but it may benbsp;well to notice some important points for the guidance of those whonbsp;may desire to collect specimens; more especially as much uncertainty exists as to afiinities and very contradictory statements arenbsp;made. The statements below may be regarded as the results ofnbsp;actual observation and of the study of specimens in situ in the rocks,nbsp;as well as in the cabinet and under the microscope.

Family Conifer.� ; Oewas Dadoxylon, Endlicher; Araucaeites, Goeppert; Aeaucarioxylon, Kraus.

The trunks of this genus occur from the Middle Devonian to the Permian inclusive, as drift-logs calcified, silicified, or pyritised. Thenbsp;only foliage associated with them is of the type of Walchia andnbsp;Araucarites�viz., slender branches with numerous small spiral acicu-lar leaves. Two of the coal-formation species, D. materiarum andnbsp;another, had foliage of this type. That of the others is unknown.nbsp;They are all distinct from the wood of �ordaites, for which see undernbsp;that genus.

D. ClarUi, Dn. (CordiBoxylon ?)... nbsp;nbsp;nbsp;�nbsp;nbsp;nbsp;nbsp;.........Report, 1883.

All of the above can be vouched for as good species based upon microscopic examination of a very large number of trunks from different parts of North America. The three Brian species of Badoxylonnbsp;and D. antiquius from the Lower Carboniferous have two or morenbsp;rows of cells in the medullary rays. The last named has severalnbsp;rows, and is a true Palmoxylon allied to B. Withami of Greatnbsp;Britain. B. materiarium is specially characteristic of the uppernbsp;coal-formation and Permian, and to it must belong one or both ofnbsp;the species of foliage indicated above. B. Clarkii has very short,nbsp;simple medullary rays of only a few cells superimposed, and has annbsp;inner cylinder of scalariform vessels, approaching in these points tonbsp;Oordaites. Ormoxylon has a very peculiar articulated pith andnbsp;simple medullary rays.

Witham in 1833 described several Carboniferous species of pine-wood, under the generic name Pinites, separating under the name Pitus species which appeared to have the discs on the cell-walls

�Geological Survey of Canada: Fossil Plants of Brian and Upper Silurian Formations,� by J. W. Dawson.

separate and in transverse lines. Witham�s name was changed bj Goeppert to Araucarites, to indicate the similarity of these woods tonbsp;Araucaria, Finites being reserved for trees more closely allied to thenbsp;ordinary pines. Endlicher, restricting Araucarites to foliage, etc.,nbsp;of Araucaria-like trees, gave the name Dadoxylon to the wood; andnbsp;this, through Unger�s � Genera and Species,� has gained somewhatnbsp;general acceptance. Endlicher also gave the name Fissadendron tonbsp;the species which Witham had called FHtus; but Brongniart proposed the name Palceoxylon to include all the species with thicknbsp;and complex medullary rays, whatever the arrangement of the discs.nbsp;In Schimper�s new work Kraus substitutes Araucarioxylon for End-licher�s Dadoxylon, and includes under Fissadendron all the speciesnbsp;placed by Brongniart in Falmoxylon.

To understand all this confusion, it may be observed that the characters available in the determination of Palseozoic coniferousnbsp;wood are chiefly the form and arrangement of the wood-cells, thenbsp;character of the bordered pores or discs of their walls, and the formnbsp;and composition of the medullary rays.

The character on which Witham separated his genus Fitus from FHnites is, as I have ascertained by examination of slices of one ofnbsp;his original specimens kindly presented to me by Mr. Sanderson, ofnbsp;Edinburgh, dependent on state of preservation, the imperfectly preserved discs or areolations of the walls of the flbre presenting thenbsp;appearance of separate and distinct circles, while in other parts ofnbsp;the same specimens these discs are seen to be contiguous and to assume hexagonal forms, so that in this respect they do not reallynbsp;differ from the ordinary species of Dadoxylon. The true characternbsp;for subdividing those species which are especially characteristic ofnbsp;the Carboniferous, is the composite structure of the medullary rays,nbsp;which are thick and composed of several radial piles of cells placednbsp;side by side. This was the character employed by Brongniart innbsp;separating the genus Falceoxylon, though he might with conveniencenbsp;have retained Witham�s name, merely transferring to the genus thenbsp;species of Witham�s Finites which have complex medullary rays.nbsp;The Brian rooks present the greatest variety of types, and Falceoxylonnbsp;is especially characteristic of the Lower Carboniferous, while speciesnbsp;of Dadoxylon with two rows of bordered pores and simple medullarynbsp;rays are especially plentiful in the upper coal-formation and Permo-Carboniferous.

The following table will clearly show the distinctive characters and relations of the genera in question, as held by the several authorsnbsp;above referred to:

Trunks marked by transverse soars of attachment of bases of leaves; leaves broad, with many parallel veins, and attached by anbsp;broad base; pistillate and staminate catkins of the nature of An-tholithes. Fruit winged or pulpy, of the kind known as Cardio-carpum. Stem with a Sternbergia pith, usually large, surrounded bynbsp;a ring of pseudo-scalariform vessels, and with a cylinder usuallynbsp;narrow, of woody wedges, with bordered pores in one or more series,nbsp;and with simple medullary rays.

From specimens kindly presented to me by Prof. Renault, I have been able to ascertain that the stems of some at least of thesenbsp;plants (Bucordaites) are distinct in structure from all the species ofnbsp;Dadoxylon, above mentioned, except D. Clarkii, of the Brian. Theynbsp;may be regarded as intermediate between those of conifers andnbsp;cycads, which is indeed the probable position of these remarkablenbsp;plants.

eeolate, sessile, entire, with rounded apices and of leathtry consistency. The leaves are from twenty to ninety centimetres in length. The nerves are either equally or unequally strong.

2. nbsp;nbsp;nbsp;Dorycordaitea.�Leaves lanceolate, with sharp points; nervesnbsp;numerous, fine, and equal in strength. The leaves attain a lengthnbsp;of from forty to fifty centimetres.

3. nbsp;nbsp;nbsp;Foacordaites.�Leaves narrow, linear, entire, blunt at thenbsp;point, with nerves nearly equally strong. The leaves are as muchnbsp;as forty centimetres in length.

This is merely a provisional genus intended to receive casts of the pith cylinders of various fossil trees. Their special peculiaritynbsp;is that, as in the modem Ceeropia peltata, and some species of Ficus,nbsp;the pith consists of transverse dense partitions which, on the elongation of the internodes, become separated from each other, so as tonbsp;produce a chambered pith cavity, the east of which shows transversenbsp;furrows. The young twigs of the modern Abies balsamifera present a similar structure on a minute scale. I have ascertained andnbsp;described such pith-cylinders in large stems of Dadoxylm Omngon-dianwm, and 1). materiarium. They occur also in the stems ofnbsp;Cordaites and probably of Sigillarim. 1 have discussed these curious fossils at length in �Acadian Geology� and in the �Journal ofnbsp;the Geological Society of London,� 1860. The following summarynbsp;is from the last-mentioned paper:

a. nbsp;nbsp;nbsp;As Prof. Williamson and the writer have shown, many ofnbsp;the Sternbergia piths belong to coniferous trees of the genus Da-doxylon.

b. nbsp;nbsp;nbsp;A few specimens present multiporous tissue, of the type ofnbsp;Dictyoxylon, a plant of unknown affinities, and which, according tonbsp;Williamson, has a Sternbergia pith.

e. Other examples show a true soalariform tissue, comparable with that of Lepidodendron or Sigillaria, but of finer texture. Cordanbsp;has shown that plants of the type of the former genus (his Loma-iophloios) had Sternbergia piths. Some plants of this group are bynbsp;external characters loosely reckoned by botanists as ribless Sigillaricenbsp;{Glathraria); but I believe that they are not related even ordinallynbsp;to that genus.

d. Many Carboniferous Sternhergim show structures identical with those described above as occurring in Cordaites, and also innbsp;some of the trees ordinarily reckoned as Sigillarice.

I have found at least eight species of these fruits in the Brian and Carboniferous of New Brunswick and Nova Scotia, all of whichnbsp;are evidently fruits of gymnospermous trees. They agree in having a dense coaly nucleus of appreciable thickness, even in thenbsp;flattened specimens, and surrounded by a thin and veinless wing ornbsp;margin. They have thus precisely the appearance of samaras ofnbsp;many existing forest-trees, some of which they also resemble in thenbsp;outline of the margin, except that the wings of samaras are usuallynbsp;veiny. The character of the nucleus, and the occasional appearancenbsp;in it of marks possibly representing cotyledons or embryos, forbidsnbsp;the supposition that they are spore-cases. They must have beennbsp;fruits of ph�nogams. Whether they were winged fruits or seeds,nbsp;or fruits with a pulpy envelope like those of cycads and somenbsp;conifers, may be considered less certain. The not infrequent distortion of the margin is an argument in favour of the latter view,nbsp;though this may also be supposed to have occurred in samaras partially decayed. On the other hand, their being always apparentlynbsp;flattened in one plane, and the nucleus being seldom, if ever, foundnbsp;denuded of its margin, are arguments in favour of their having beennbsp;winged nutlets or seeds. Until recently I had regarded the latternbsp;view as more probable, and so stated the matter in the second edition of � Acadian Geology.� I have, however, lately arrived at thenbsp;conclusion that the Cardiocarpa of the type of G. comutum werenbsp;gymnospermous seeds, having two cotyledons embedded in an albumen and covered with a strong membranous or woody tegmen surrounded by a fleshy outer coat, and that the notch at the apex represents the foramen or micropyle of the ovule. The structure wasnbsp;indeed very similar to that of the seeds of Taxm and of Salisburia.nbsp;With respect to some of the other species, however, especially thosenbsp;with very broad margins, it still appears likely that they were winged.

The Cardiocarpa were borne in racemes or groups, and it seems certain that some of them at least are the seeds of Cordaites. Thenbsp;association of some of them and of those of the next genus withnbsp;Sigillarim is so constant that I cannot doubt that some of themnbsp;belong to plants of that genus, or possibly to taxine conifers. Thenbsp;great number of distinct species of these seeds, as compared withnbsp;that of known trees which could have produced them, is very remarkable.

These are large angled nuts contained in a thick envelope, and showing internal structures resembling those of the seeds of modern

Taxinem. There are numerous species, as well as allied seeds referred to the provisional genera Rhabdocarpus and Carpolithes. In Trigonocarpum Hookeri I have described the internal structurenbsp;of one of those seeds, and many fine examples from the coal-field ofnbsp;St. Etienne, in France, have been described by Brongniart, so thatnbsp;their internal structure is very well known.

This is also a provisional genus, to include spikes of floral organs, some of which are known to have belonged to Cordaites,nbsp;others probably to Sigillarim.

Under this name pal�obotanists have included a great number of trees of the Carboniferous system, all of which are characterisednbsp;by broad leaf-sears, witli three vascular scars, and usually arrangednbsp;in vertical rows, and by elongated three-nerved leaves, and roots ofnbsp;the stigmaria type�that is, with rounded pits, marking the attachment of rootlets spirally arranged. These trees, however, collectednbsp;in the genus Sigillaria by arbitrary characters, which pass intonbsp;those of the Lepidodendroid trees, have been involved in almost inextricable confusion, to disentangle which it will be necessary to consider : 1. The external characters of Sigillarim, and trees confoundednbsp;with them. 3. Subdivision of Sigillarim by external markings. 3.nbsp;The microscopic character of their stems. 4. What is known ofnbsp;their foliage and fruit.

It may be premised that the modes of determination in fossil botany are necessarily different from those employed in recent botany. The palajobotanist must have recourse to characters derivednbsp;from the leaves, the scars left by their fall, and the internal structures of the stem. These parts, held in little esteem by botanists innbsp;describing modem plants, and much neglected by them, must holdnbsp;the first place in the regard of the fossil botanist, whereas the fructification, seldom preserved, and generally obscure, is of comparatively little service. It is to be remarked also that in such generalised plants as those of the Palaeozoic, remarkable rather for the development of the vegetative than of the reproductive organs, thenbsp;former rise in importance as compared with their value in the studynbsp;of modern plants.

In Sigiilarim, Lepidodendra, amp;e., the following surfaces of the stem may be presented to our inspection :

1. The outer surface of the epidermis without its leaves, but with the leaf-bases and leaf-scars more or less perfectly preserved.nbsp;On this surface we may recognise: (1) Cellular swellings or projections of the bark to which the leaves are attached. These may benbsp;called leaf-bases, and they are sometimes very prominent. (S) Thenbsp;actual mark of the attachment of the leai situated in the mostnbsp;prominent part of the leaf-base. This is the leaf-scar. (3) In thenbsp;leaf-soar when well preserved we can see one or more minute punctures or prominences which are the points where the vascular bundlesnbsp;passing to the leaf found exit. These are the vascular scars.

When the leaves are attached, the leaf-scars and vascular scars cannot be seen, but the leaf-bases can be made out. Hence it isnbsp;important, if possible, to secure specimens with and without thenbsp;leaves. In flattened specimens the loaf-bases are often distorted bynbsp;pressure and marked with furrows which must not be mistaken fornbsp;true structural characters. The leaf-bases, which are in relief on thenbsp;outer surface of the stem, of course appear as depressions on thenbsp;mould in the containing rook, in which the markings often appearnbsp;much more distinctly than on the plant itself.

3. The outer surface of the epidermis may have been removed or may be destroyed by the coarseness of the containing rock. In thisnbsp;case the leaf-bases are usually preserved on the surface of the outernbsp;or corky bark, but the leaf-scars and vascular scars have disappeared.nbsp;This gives that condition of Lepidodendroid trees to which the namenbsp;Knorria has been applied. When plants are in this state careful inspection may sometimes discover traces of the leaf-soars on portionsnbsp;of the stem, and thus enable the Knorria to be connected with thenbsp;species to which it belongs.

3. The outer or corky bark may be removed, exposing the surface of the inner or fibrous and cellular bark, which in the plants in question is usually of great thickness. In this case neither the leaf-bases nor the scars are seen, but punctures or little furrows or ridgesnbsp;appear where the vascular bundles entered the inner bark. Specimens in this state are usually said to be decorticated, though onlynbsp;the outer bark is removed. It is often difflcult to determine plantsnbsp;in this condition, unless some portion of the stem can be found stillnbsp;retaining the bark; but when care is taken in collecting, it will notnbsp;infrequently be found that the true outer surface can be recoverednbsp;from the containing rook, especially if a coaly layer representing thenbsp;outer bark intervenes between this and the inner impression. Speei-

mens of this kind, taken alone, have been referred to the genera Knorria, Bothrodendron, and Halonia.

4 In some cases, though not frequently, the outer surface of the ligneous cylinder is preserved. It almost invariably presents anbsp;regularly striated or irregularly wrinkled appearance, dependingnbsp;upon the vertical woody wedges, or the positions of the medullarynbsp;rays or vascular bundles. Specimens of this kind constituted somenbsp;of the Endogenites of the older botanists, and the genus ScJiizoden-dron of Eichwald appears to include some of them. Many of themnbsp;have also been incorrectly referred to Calamites.

5. In some cases the oast of the medullary cylinder or pith may alone be preserved. This may be nearly smooch or slightly markednbsp;by vertical striae, but more usually presents a transverse striation,nbsp;and not infrequently the transverse constrictions and septa characteristic of the genus Sternbergia. Loose SUrnbergioz aSord littlenbsp;means of connecting them with the species to which they belong,nbsp;except by the microscopic examination of the shreds of the ligneousnbsp;cylinder which often cling to them.*

These facts being premised, the following general statements may be made respecting some of the more common Palaeozoic genera,nbsp;referring, however, principally to the perfect markings as seen onnbsp;the epidermis;

Sigillaria.�Leaf-bases hexagonal or elongated, or confluent on a vertical ridge. Leaf-scars hexagonal or shield-shaped. Vascularnbsp;scars three, the two lateral larger than the central. This last character is constant, depending on the fact that the leaves of Sigillarianbsp;have two or more vascular bundles. All so-called Sigillaria havingnbsp;the central vascular scar largest, or only one vascular bundle, shouldnbsp;be rejected from this genus. In young branches of branching Sigillaria. the leaf-sears sometimes appear to be spiral, but in the oldernbsp;stems they form vertical rows; interrupted, however, by transversenbsp;rows or bands of fruit-scars, each with a single large central vascularnbsp;scar, and which have borne the organs of fructification. Arthro-eaulis of McCoy is founded on this peculiarity.

Syringodendron.�Differs from Sigillaria in the leaf-scars, which are circular and with a single vascular bundle. It is a matter ofnbsp;doubt whether these plants were of higher rank than Sigillarianbsp;tending toward the pines, or of lower rank tending toward Cyclostigma. Their leaf-bases form vertical ridges.

Lepidodendron.�Leaf-bases rhombic, oval, or lanceolate, moder-� See my paper, � Journal of Geological Society,� vol. xxvii.

ately prominent. Leaf-scars rhombic or sometimes shield-shaped or heart-shaped, in the middle or upper part of the leaf-base. Vascularnbsp;scars three�the middle one always largest and corresponding to thenbsp;single nerve of the leaf; the lateral ones sometimes obsolete.

In older stems three modes of growth are observed. In some species the expansion of the bark obliterates the leaf-bases andnbsp;causes the leaf-scars to appear separated by wide spaces of more ornbsp;less wrinkled bark, which at length becomes longitudinally furrowednbsp;and simulates the ribbed character of Sigillaria. In others the leaf-bases grow in size as the trunk expands, so that even in large trunksnbsp;they are contiguous though much larger than those on the branches.nbsp;In others the outer bark, hardening at an early age, is incapable ofnbsp;either of the above changes, and merely becomes cleft into deep furrows in the old trunks.

LepidopMoios.�Leaf-bases transverse and prominent � often very much so. Leaf-scars transversely rhombic or oval with threenbsp;vascular scars, the central largest. Leaves very long and one-nerved. Large strobiles or branohlets borne in two ranks or spirallynbsp;on the sides of the stem, and leaving large, round soars (cone-scars),nbsp;often with radiating impressions of the basal row of scales.

Species with long or drooping leaf-bases have been included in LepidopMoios and Lomatophloios. Species with short leaf-bases andnbsp;cone-scars in two rows have been called Ulodendron, and some ofnbsp;them have been included in Sigillaria (sub-genus Glathraria). Decorticated stems are Botlirodendron and Halonia. Some of thenbsp;species approach near to the last genus, especially to the Lepidoden-dra with rhombic leaf-bases like L. tetragonum.

Cyelostigma. � Leaf-bases undeveloped. Leaf-sears circular or horseshoe-shaped, small, with a central vascular scar. In old trunksnbsp;of Cyclostigma the leaf-scars become widely separated, and sometimes appear in vertical rows. Young branches of Lepidodendronnbsp;sometimes have the leaf-scars similar to those of Cyclostigma.

Leptophleum. � Leaf-bases flat, rhombic; leaf-scars obsolete; vascular scar single, central. The last two genera are characteristically Devonian.

In contradistinction from the trees above mentioned, the following general statements may be made respecting other groups:

In conifers the leaf-bases are usually elongated vertically, often scaly in appearance, and with the leaf-scar terminal and round, oval,nbsp;or rhombic, and with a single well-marked vascular scar.

In Calamites, Calamodendron, and Asterophyllites the scars of the branohlets or leaves are circular or oval, with only a single vas-

cular scar, and situated in verticils at the top of well-marked nodes of the stem.

In tree-ferns the leaf-bases are large and usually without a distinct articulating surface. The vascular bundles are numerous. Protopteris has rounded leaf-scars with a large horseshoe-shapednbsp;bundle of vessels above and small bundles below. Caulopteris hasnbsp;large elliptic or oval leaf-scars with vascular soars disposed concentrically. Palffiopteris,¹ of Geinitz, has the leaf-scars transverselynbsp;oval and the vascular bundles confluent in a transverse band with annbsp;appendage or outlying bundle below. Stemmatopteris has leaf-sears similar to those of Caulopteris, but the vascular bundles unitednbsp;into a horseshoe-shaped band.

The following groups may be defined in this way; but, being based on one character only, they are of course in all probability farnbsp;from natural:

1. nbsp;nbsp;nbsp;Sigillaria, Brongniart. Type, Sigillaria renifomiis, Bron-gniart, or S. Brounii, Dawson.�Stem with broad ribs, usually muchnbsp;broader than the usually oval or elliptical tripunctate areoles, butnbsp;disappearing at base, owing to expansion of the stem. Leaves narrow, long, three-nerved.

2. nbsp;nbsp;nbsp;Rhytidolepis, Sternberg. Type, S. scutellata, Brongniart.�nbsp;Bibs narrow, and often transversely striate. Areoles large, hexagonal or shield-shaped, tripunctate. Leaves as in last group. Bingsnbsp;of rounded scars on the stems and branches mark attachment ofnbsp;fruit. It is possible that some of the smaller stems of this groupnbsp;may be branches of trees of group first.

3. nbsp;nbsp;nbsp;Syringodendron, Sternberg. Type, S. organum, L. and H.,nbsp;S. oculata, Brongniart.�Stems ribbed; areoles small and round,nbsp;and apparently with a single scar, or three closely approximated.nbsp;These are rare, and liable to be confounded with decorticated examples of other groups; but I have some specimens which unquestionably represent the external surface.

4. nbsp;nbsp;nbsp;Favularia, Sternberg. Type, Sigillaria elegans of Brongniart.�Leaf-bases hexagonal, or in young branches elliptical, in verticalnbsp;rows, but without distinct ribs, except in old or decorticated stems.nbsp;Bruit borne in verticils on the branches bearing transverse rows ofnbsp;rounded soars. Leaves somewhat broad and longitudinally striate.

This name, preoccupied by Geinitz, has been inadvertently misapplied to the Devonian ferns of the genus Archmopteris,

5. nbsp;nbsp;nbsp;Leioderrm, GoHenberg. Type, S. Sydnensis, Dawson. �nbsp;Ribs obsolete. Cortical and ligneous surfaces striate. Vascularnbsp;scars double, elongate longitudinally, and alike on cortical and innernbsp;surfaces. Areoles in rows and distinct; stigmaria-roots striate, withnbsp;small and distinct areoles.

6. nbsp;nbsp;nbsp;Qlaihraria, Brongniart. Type, S. Menardi, Brongniart.�nbsp;Areoles hexagonal, not in distinct rows, but having a spiral appearance. Some of the plants usually referred to this group are probablynbsp;branches of Favularia. Others are evidently fragments of plantsnbsp;of the genus Lepidophloios.

I long ago pointed out, on the evidence of the external markings and mode of growth, that the stems of Sigillarim must have beennbsp;exogenous, and this conclusion has now been fully confirmed by thenbsp;microscopic researches of Williamson, not only in the case of Sigil-larice, but of Lepidodendra and Calamodendra as well. Confiningnbsp;myself to my own observations, three types of Sigillaria are knownnbsp;to me by their internal structures, though I cannot certainly correlate all of these with the external markings referred to above.

1. Diploxylon, in which the stem consists of a small internal axis surrounded by a very thick inner bark and a dense outer cortex.nbsp;A fine example from the South Joggins is thus described: *

� The axis of the stem is about six centimetres in its greatest diameter, and consists of a central pith-cylinder and two concentric coats of soalariform tissue. The pith-cylinder is replacednbsp;by sandstone, and is about one centimetre in diameter. The innernbsp;cylinder of scalariform tissue is perfectly continuous, not radiated,nbsp;and about one millimetre in thickness. Its vessels are somewhatnbsp;crushed, but have been of large diameter. Its outer surface, whichnbsp;readily separates from that of the outer cylinder, is striated longitudinally. The outer cylinder, which constitutes by much thenbsp;largest part of the whole, is also composed of scalariform tissue;nbsp;but this is radially arranged, with the individual cells quadrangularnbsp;in cross-section. The cross-bars are similar on all the sides andnbsp;usually simple and straight, but sometimes branching or slightlynbsp;reticulated. The wall intervening between the bars has extremelynbsp;delicate longitudinal waving lines of ligneous lining, in the mannernbsp;first described by Williamson as occurring in the scalariform tissuenbsp;of certain Lepidodendra. A few small radiating spaces, partially

occupied with pyrites, obscurely represent the medullary rays, which must have been very feebly developed. The radiating bundlesnbsp;passing to the leaves run nearly horizontally; but their structurenbsp;is very imperfectly preserved. The stem being old and probablynbsp;long deprived of its leaves, they may have been partially disorganisednbsp;before it was fossilised. The outer surface of the axis is striatednbsp;longitudinally, and in some places marked with impressions of tortuous fibres, apparently those of the inner bark. In the cross-section, where weathered, it shows concentric rings; but under thenbsp;microscope these appear rather as bands of compressed tissue thannbsp;as proper lines of growth. They are about twenty in number. Thisnbsp;tree has an erect, ribbed trunk, twelve feet in height and fifteennbsp;inches in diameter, swelling to about two feet at the base.

2. nbsp;nbsp;nbsp;Favularia Type.�This has been well described by Brongniartnbsp;and by Kenault,¹ and differs from the above chiefly in the fact thatnbsp;the outer exogenous woody zone is composed of reticulated insteadnbsp;of scalariform tissue, and the inner zone is of the peculiar formnbsp;which I have characterised as pseudo-scalariform.

3. nbsp;nbsp;nbsp;Sigillaria Proper.�This I have illustrated in my paper innbsp;the � Journal of the Geological Society � for May, 1871, and it appears to represent the highest and most perfect type of the largernbsp;ribbed Sigillaria. This structure I have described as follows, basing my description on a very fine axis found in an erect stem, andnbsp;on the fragments of the woody axis found in the bases of other erectnbsp;stems:

a. nbsp;nbsp;nbsp;A dense cellular outer bark, usually in the state-of compactnbsp;coal�but when its structure is preserved, showing a tissue of thickened parenchymatous cells.

b. nbsp;nbsp;nbsp;A very thick inner bark, which has usually in great partnbsp;perished, or been converted into coal, but which, in old trunks, contained a large quantity of prosenchymatous tissue, very tough andnbsp;of great durability. This � bast-tissue � is comparable with that ofnbsp;the inner bark of modern conifers, and constitutes much of the mineral charcoal of the coal-seams.

e. An outer ligneous cylinder, composed of wood-cells, either with a single row of large bordered pores,f in the manner of pines

f These are the same with the wood-cells elsewhere called discigerous tissue, and to which I have applied the terms uniporous and multiporous.nbsp;The markings on the walls are caused by an unlined portion of the cell-wall placed in a disk or depression, and this often surrounded by an

and cycads, or with two, three, or four rows of such pores sometimes inscribed in hexagonal areoles in the manner of Dadoxylon. Thisnbsp;woody cylinder is traversed by medullary rays, which are short, andnbsp;composed of few rows of cells superimposed. It is also traversed bynbsp;oblique radiating bundles of pseudo-sealariform tissue proceeding tonbsp;the leaves. In some Sigillarim this outer cylinder was itself in partnbsp;composed of pseudo-sealariform tissue, as in Brongniart�s specimennbsp;of S. elegans ; and in others its place may have been taken by mul-tiporous tissue, as in a case above referred to; but I have no reasonnbsp;to believe that either of these variations occurred in the typicalnbsp;ribbed species now in question. The woody fibres of the outernbsp;cylinder may be distinguished most readily from those of conifers,nbsp;as already mentioned, by the thinness of their walls, and the morenbsp;irregular distribution of the pores. Additional characters are furnished by the medullary rays and the radiating bundles of soalari-form tissue when these can be observed.

d. nbsp;nbsp;nbsp;An inner cylinder of pseudo-sealariform tissue, I havenbsp;adopted the term pseudo-sealariform for this tissue, from the conviction that it is not homologous with the scalariform ducts of fernsnbsp;and other aorogens, but that it is merely a modification of the dis-cigerous wood-cells, with pores elongated transversely, and sometimesnbsp;separated by thickened bars, corresponding to the hexagonal areo-lation of the ordinary wood-cells. A similar tissue exists in cycads,nbsp;and is a substitute for the spiral vessels existing in ordinary exogens.

e. nbsp;nbsp;nbsp;A large medulla, or pith, consisting of a hollow cylinder ofnbsp;cellular tissue, from which proceed numerous thin diaphragms towards the centre of the stem.

These structures of the highest type of Sigillaria are on the one hand scarcely advanced beyond those of Calamopitus, as described by Williamson, and on the other approach to those ofnbsp;Cordaiies, as seen in specimens presented to me by Renault.

Finally, as to the fruit of SigillaricB, I have no new facts to offer. The strobiles or spikes associated with these trees have beennbsp;variously described as gymnospermous (Renault) or eryptogamousnbsp;(Goldenberg and Williamson). 1 have never seen them in place.nbsp;Two considerations, however, have always weighed with me in reference to this subject. One is the constant abundance of Trigonocarpanbsp;hexagonal rim of thickened wall; but in all cases these structures arenbsp;less pronounced than in Dadoxylon^ and less regular in the walls of thenbsp;same cell, as well as in different layers of the tissues of the axis.

and Cardiocarpa in the soil of the Sigillaria forests, as I have studied this at the South Joggins. The other is that the rings of fruit-soarsnbsp;on the branches of Sigillaria are homologous with leaf-scars, notnbsp;with branches, and therefore should haye borne single carpels andnbsp;not cones or spikes of inflorescence. These are merely suggestions,nbsp;but I have no doubt they will be vindicated by future discoveries,nbsp;which will, I have no doubt, show that in the family SigillariacecBnbsp;we have really two families, one possibly of gymnospermous rank,nbsp;or at least approaching to this, the other allied to the Lepidodendra.

These are arboreal Lycopods having linear one-nerved leaves, stems branching diehotomously, and with ovate or rhombic leaf-basesnbsp;bearing rhombic leaf-sears, often very prominent. The fruit is innbsp;scaly strobiles, terminal or lateral, and there are usually, if notnbsp;always, maerospores and microspores in each strobile. The youngnbsp;branches and stems have a central pith, a cylinder of scalariformnbsp;tubes sending out ascending bundles to the leaves through a thicknbsp;cellular and fibrous inner bark, and externally a dense cortex confluent with or consisting of the leaf-bases. Older stems have a second ornbsp;outer layer of scalariform fibres in wedges with medullary rays, andnbsp;strengthening the stem by a true exogenous growth, much as in thenbsp;Diploxylon type of Sigillaria. The development of this exogenousnbsp;cylinder is different in amount and rate in different species.¹ Thisnbsp;different development of the exogenous axis is accompanied withnbsp;appropriate external appearances in the stems, and the changesnbsp;which take place in their markings. These are of three kinds. Innbsp;some species the areoles, at first close together, become, in the process of the expansion of the stem, separated by intervening spaces ofnbsp;bark in a perfectly regular manner; so that in old stems, while widelynbsp;separated, they still retain their arrangement, while in young stemsnbsp;they are quite close to one another. This is the case in L. corruga-tum. In other species the leaf-scars or bases increase in size in thenbsp;old stems, still retaining their forms and their contiguity to eachnbsp;other. This is the case in L. v/ndulatum, and generally in thosenbsp;Lepidodendra which have large leaf-bases. In these species the

See � Memoirs of Dr. Williamson,� in �Philosophical Transactions,� for ample details.

continued vitality of the bark is shown by the occasional production of lateral strobiles on large branches, in the manner of the modemnbsp;red pine of America. In other species the areoles neither increase innbsp;size nor become regularly separated by growth of the interveningnbsp;bark; but in old stems the bark splits into deep furrows, betweennbsp;which may be seen portions of bark still retaining the areoles innbsp;their original dimensions and arrangement. This is the case withnbsp;L. Pictoense. This cracking of the bark no doubt occurs in very oldnbsp;trunks of the first two types, but not at all to the same extent.

As a type of Lepidodendron, I may describe one of the oldest Carboniferous species characteristic of the Lower Carboniferous innbsp;America, and corresponding to L. Veltheimianum of Europe.

Lepidodendron Coerdgatum, Lawson.�(See Eig. 43, supra.) � Quarterly Journal of Geological Society,� vol. xv.; � Acadian Geology,� page 451.

Habit of Growth.�Somewhat slender, with long branches and long, slender leaves having a tendency to become horizontal ornbsp;drooping.

Markings of Stem.�Leaf-bases disposed in quincunx or spirally, elongate, ovate, acute at both ends, but more acute and slightlynbsp;oblique at the lower end; most prominent in the upper third, andnbsp;with a slight vertical ridge. Leaf-sears small, rounded, and showingnbsp;only a single punetiform vascular scar. The leaf-scar on the outernbsp;surface is in the upper third of the base; but the obliquity of thenbsp;vascular bundle causes it to be nearly central on the inside of thenbsp;epidermis. In young succulent shoots the leaf-scars are contiguousnbsp;mid round as in Cyclostigma, without distinct leaf-bases. In thisnbsp;state it closely resembles L. Olivieri, Bichwald.¹

In the ordinary young branches the leaf-scars are contiguous, and closely resemble those of L. elegans, Brongt. (Pig. 43 C). As thenbsp;branches increase in diameter the leaf-scars slightly enlarge andnbsp;sometimes assume a verticillate appearance (Pig. 43 D). As theynbsp;still further enlarge they become separated by gradually increasingnbsp;spaces of bark, marked with many waving stri� or wrinkles (Pig.nbsp;43 I, N). At the base of old stems the bark assumes a generallynbsp;Wrinkled appearance without distinct soars.

Knorria or Decorticated States.�Of these there is a great variety, depending on the state of preservation, and the particular longitudinal ridges. Pig. 43 D shows a form in which the vascular bundles appear as cylindrical truncate projections. Other forms show

the leaf-bases prominent, or have an appearance of longitudinal ribbing produced by the expansion of the bark.

Structure of Stem.�This is not perfectly preserved in any of my specimens, but one flattened specimen shows a central medullanbsp;with a narrow ring of scalariform vessels surrounding it, and constituting the woody axis. The structure is thus similar to that of L.nbsp;Harcourtii, which I regard as probably the same with the closelynbsp;allied European species L. Veltheimianum.

Leaves.�These are narrow, one-nerved, curving somewhat rapidly outward (Pigs. 43, B, C, D). They vary from one to two inches in length.

Loots.�I have not seen these actually attached, but they occur very abundantly in the underclays of some erect forests of the.senbsp;plants at Horton Bluff, and are of the character of Stigmariw (Pigs.nbsp;30, 31). In some of the underolays the long, flattened rootlets are excessively abnndant, and show the mark of a central vascular bundle.

Fructification.�Cones terminal, short, with many small, acute imbricate scales. Spore-cases globular, smooth (Pig. 43 C). Onnbsp;the surface of some shales and sandstones at Horton there are innumerable round spore-cases of this tree about the size of mustard-seednbsp;(Pig. 43 P). Large slabs are sometimes covered with these, and thinnbsp;layers of shale are filled with flattened specimens.

This is the characteristic species of the Lower Carboniferous coal-measures, occurring in great profusion at Horton Bluff and its vicinity, also at Sneid�s Mills near Windsor, Noel and Five-Milenbsp;Kiver, at Norton Creek and elsewhere in New Brunswick (Matthew�snbsp;coUeotion), and at Antigonish (Honeyman�s collection).

I have received from the lowest Carboniferous beds of Ohio specimens of this species.¹ According to Rogers and Lesquereux similar forms occur in the Vespertine of Pennsylvania and in the Lowernbsp;Carboniferous of Illinois. L. Veltheimianum of western Europenbsp;and L. glincanum of Russia are closely allied Lower Carboniferousnbsp;species, f

A very different type is furnished by a new species from the middle coal-formation of Clifton, New Brunswick.

Lepidodendeon Cliftonense, Dawson. � Habit of Growth.� Robust, with thick branches, and leaves several inches in length.nbsp;Terminal branches becoming slender, with shorter leaves.

�Journal of Geological Society,� November, 1862, p. 313. f For comparisons of these see � Report on Plants of Lower Carboniferous of Canada,� p. 21.

Markings of Stem.�Leaf-bases long oval, pointed at ends, enlarging with growth of stem. Leaf-scars central, rhombic, transverse.

Leaves.�One-nerved, acutely pointed, from four inches in length on the larger branches to one inch or less on the branchlets.

Fructification.�Cones large, cylindrical or long oval, with large scales of trigonal form, and not elongated but lying close to the surface. Borne on lateral, slender branchlets, with short leaves.

Lepidophloios.�Under this generic name, established by Sternberg, I include those lycopodiaceous trees of the coal-measures which have thick branches, transversely elongated leaf-scars, eachnbsp;with three vascular points and placed on elevated or scale-like protuberances, long one-nerved leaves, and large lateral strobiles in vertical rows or spirally disposed. Their structure resembles that ofnbsp;Lepidodendron, consisting of a Sternbergia pith, a slender axis ofnbsp;large soalariform vessels, giving off from its surface bundles ofnbsp;smaller vessels to the leaves, a very thick cellular bark, and a thinnbsp;dense outer bark, having some elongated cells or bast-tissue on itsnbsp;inner side. In these trees the exogenous outer cylinder is less developed than in the Lepidodendra, and is sometimes wanting innbsp;stems or branches of some thickness.

Regarding L. laricinum of Sternberg as the type of the genus, and taking in connection with this the species described by Golden-berg, and my own observations on numerous specimens found innbsp;Nova Scotia, 1 have no doubt that Lomatophloios crassicaulis ofnbsp;Corda, and other species of that genus described by Goldenberg,nbsp;TJlodendron and Bothrodendron of Lindley, Lepidodendron ornatis-simwm of Brongniart, and Halonia punctata of Geinitz, all belongnbsp;to this genus, and differ from each other only in conditions ofnbsp;growth and preservation. Several of the species of Lepidostrohusnbsp;and Lepidophyllum also belong to Lepidophloios.

The species of Lepidophloios are readily distinguished from Lepidodendron by the form of the areoles, and by the round scars onnbsp;the stem, which usually mark the insertion of the large strobiles,nbsp;though in barren stems they may also have produced branches; still,nbsp;the fact of my finding the strobiles in situ in one instance, the accurate resemblance which the scars bear to those left by the cones ofnbsp;the red pine when borne on thick branches, and the actual impressions of the radiating scales in some specimens, leave no doubt in my

mind that they are nsnally the marks of cones; and the great size of the cones of Lepidophloios accords with this conclusion.

The species of LepidopMoioa are numerous, and individuals are quite abundant in the coal formation, especially toward its uppernbsp;part. Their flattened bark is frequent in the coal-beds and theirnbsp;roofs, affording a thin layer of pure coal, which sometimes shows thenbsp;peculiar laminated or scaly character of the bark when other characters are almost entirely obliterated. The leaves also are nearly asnbsp;abundant as those of Sigillaria in the coal-shales. They can readilynbsp;be distinguished by their strong, angular mid-rib.

The markings of LepidopMoios may easily be mistaken for those of the Glathraria type of Sigillaria. When the stem only is seen,nbsp;they can be distinguished by the length of the leaf-bases in Lepi-dophloios, and by the dominant central vascular scar; also by thenbsp;one-nerved and ribbed leaves. Where the large, round marks of thenbsp;cones are present, these are an infallible guide, never being presentnbsp;in Sigillaria. As the cones grew on the upper sides of the branches,nbsp;the impression of the lower side often shows no cone-scars, or onlynbsp;two lateral rows, whereas on the upper side of the same branch theynbsp;appear spirally arranged. I may describe as an example�

LepidopMoios Acadianus, Dawson. Leaf-bases broadly rhombic, or in old stems regularly rhombic, prominent, ascending, terminated by very broad rhombic scars having a central point and two lateral obscure points. Outer bark laminated or scaly. Surface ofnbsp;inner bark with single points or depressions. Leaves long, linear,nbsp;with a strong keel on one side, five inches or more in length. Cone-soars sparsely scattered on thick branches, either in two rows ornbsp;spirally, both modes being sometimes seen on the same branch.nbsp;Scalariform axis scarcely an inch in diameter in a stem live inchesnbsp;thick. Fruit, an ovate strobile with numerous acute scales coveringnbsp;small globular spore-cases. This species is closely allied to TJloden-dron majus and LepidopMoios laricmus, and presents numerousnbsp;varieties of marking. Coal-formation, Nova Scotia.

The plants of this genus are unquestionably allied to the modem Equisetacem, but excel these so much in variety of form and structure, and are so capricious in their states of preservation, and sonbsp;liable to be mistaken for parts of plants generically different, thatnbsp;they have given rise to much controversy. The following considerations will enable us to arrive at some certainty.

dinally ribbed and jointed stems so frequent in the coal-formation, and of which the common C. Suckovii is a tyJ)ioal form. The mostnbsp;perfect of these stems represent the outer surface immediately withinnbsp;the epidermis, in which case transverse lines or constrictionsnbsp;mark the nodes, and at the nodes there are rounded spots, sometimes indicating radial processes of the pith, first described bynbsp;Williamson; in other eases, the attachment of branchlets, or in somenbsp;specimens both. But some specimens show the outer surface of thenbsp;epidermis, in which case the transverse nodal lines are usually invisible, though the scars of branchlets may appear. In still othernbsp;examples the whole of the outer tissues have perished, and the so-called Calamite is a cast of the interior of the stem, showing merelynbsp;longitudinal ribbing and transverse nodal constrictions. In studying these plants in situ in the erect Calamite brakes of the coal-formation of Nova Scotia, one soon becomes familiar with these appearances, but they are evidently unknown to the majority of palaeo-botanists, though described in detail more than twenty years ago.

When the outer surface is preserved it is sometimes seen to bear verticils of long needle-like leaves (G. Oistii), or of branchlets withnbsp;secondary whorls of similar leaves ((7. Suckovii and O. umdulatus).nbsp;No Calamite known to me bears broad one-nerved leaves like thosenbsp;of Asterophyllites and Annularia, though the larger stems of thesenbsp;plants have been described as Catamites, and the term Calamocladusnbsp;has been used to include both groups. The base of the Calamitenbsp;stem usually terminates in a blunt point, and may be attached to anbsp;rhizome, or several stems may bud out from each other in a group ornbsp;stool. The roots are long and cylindrical, sometimes branching.nbsp;The fruit consists of spikes of spore-cases, borne in whorls and subtended by linear floral leaves. To these strobiles the name Calamo-stachys has been given.

Williamson has shown that the stem of Catamites consists of a central pith or cavity of large size surrounded by a cylinder consisting of alternate wedges of woody and cellular matter, with vertical canals at the inner sides of the wedges, and slender medullarynbsp;rays. The thick cellular wedges intervening between the woodynbsp;wedges he calls primary medullary rays; the smaller medullarynbsp;rays in the wedges, secondary medullary rays. There is thus anbsp;highly complex exogenous stem based on the same principle withnbsp;the stem of a common Equisetum, but with much greater strength �nbsp;and complexity.

Williamson has also shown that there are different sub-types of these stems. More especially he refers to the three following:

(a) Calamites proper, which has the woody wedges of soalari-form or barred tissue with thin medullary rays, and the thick primary medullary rays are cellular.

(h) Calamopitus has reticulated or multiporous tissue in the woody wedges with medullary rays, and the primary medullarynbsp;wedges are composed of elongated cells.

(c) nbsp;nbsp;nbsp;Cala/modendron has the woody wedges of barred tissue as innbsp;a, with medullary rays, but has the intervening medullary wedgesnbsp;of an elongated tissue approaching to woody fibre, and also withnbsp;medullary rays.

To these I would add a fourth type, which I have described, from the coal-formation of Nova Scotia.¹

(d) nbsp;nbsp;nbsp;Eucalamodendron differs from Galamodendron in havingnbsp;true bordered pores or pseudo-scalariform slit-pored tissue, and corresponds to the highest type of calamitean stem.

I would also add that under a and i there are some species in which the woody cylinder is very thin in comparison to the size ofnbsp;the stem. In c and d the woody cylinder is thick and massive, andnbsp;the stems are often large and nodose.

As an example of an ordinary Calamite in which the external surface and foliage are preserved, I may quote the following fromnbsp;my report on the � Flora of the Lower Carboniferous and Millstonenbsp;Grit,� 1873:

Calamites Undulatus, Brongniart.�This species is stated by Brongniart to be distinguished from the G. Suckovii, the characteristic Calamite of the middle coal-formation, by its undulated ribsnbsp;marked with peculiar cellular reticulation. He suggests that it maynbsp;be merely a variety of G. Suckovii, an opinion in which Schimpernbsp;coincides; but since 1 have received large additional collections fromnbsp;Mr. Elder, containing not only the stems and branches, but also thenbsp;leaves and rhizomes, I am constrained to regard it as a distinctnbsp;though closely allied species.

The rhizomata are slender, being from one to two inches in diameter, and perfectly flattened. They are beautifully covered withnbsp;a cellular reticulation on the thin bark, and show occasional roundnbsp;areoles marking the points of exit of the rootlets. I have long beennbsp;familiar with irregular flattened stems thus reticulate, but have onlynbsp;recently been able to connect them with this species of Calamite.

The main stems present a very thin carbonaceous bark reticulated like the rhizomes. They have flat, broad ribs separated by deep

and narrow furrows, and undulated in a remarkable manner even when the stems are flattened. This undulation is, however, perhaps annbsp;indication of vertical pressure while the plant was living, as it seemsnbsp;to have had an unusually thin and feeble cortical layer, and the undulations are apparently best developed in the lower part of the stem.nbsp;At the nodes the ribs are often narrowed and gathered together,nbsp;especially in the vicinity of the rounded radiating marks which appear to indicate the points of insertion of the branches. At the topnbsp;of each rib we have the usual rounded areole, probably marking thenbsp;insertion of a primary branchlet.

The branches have slender ribs and distant nodes, from which spring secondary branchlets in whorls, these bearing in turn smallnbsp;whorls of acicular leaflets much curved upward, and which are apparently round in cross section and delicately striate. They arenbsp;much shorter than the leaves of Calamites Suckovii, and are lessnbsp;dense and less curved than those of lt;7. nodosus, which I believe to benbsp;the two most closely allied species.

Lesquereux notices this species as characteristic of the lower part of the Carboniferous in Arkansas.

It will be observed that I regard the striated and ribbed stems not as internal axes, but as representing the outer surface of the plants.nbsp;This was certainly the case with the present species and with C.nbsp;Suckovii and O. nodosus. Other species, and especially those whichnbsp;belonged to Calamodendron, no doubt had a smooth or irregularlynbsp;wrinkled external bark; but this gives no good ground for the manner in which some writers on this subject confound Calamites withnbsp;Calamodendra, and both with Asterophyllites and Sphenophyllum.nbsp;With this no one who has studied these plants, rooted in their nativenbsp;soils, and with their appendages still attached, can for a momentnbsp;sympathise. One of the earliest geological studies of the writer wasnbsp;a bed of these erect Calamites, which he showed to Sir C. Lyell innbsp;1844, and described in the � Proceedings of the Geological Society �nbsp;in 1851, illustrating the habit of growth as actually seen well exposed in a sandstone oliflquot;. Abundant opportunities of verifying,nbsp;the conclusions formed at that time have since occurred, the resultsnbsp;of which have been summed up in the figures in Acadian Geology,nbsp;which, though they have been treated by some botanists as merelynbsp;restorations, are in reality representations of facts actually observed.

On these subjects, without entering into details, and referring for these to the elaborate discussions of Sohimper, Williamson, andnbsp;McNab, and to my paper on the subject, � Journal of the Geologicalnbsp;Society,� vol. xxvii, p. 54, I may remark :

1. nbsp;nbsp;nbsp;That the aerial stems of ordinary Calamites had a thin corticalnbsp;layer, with lacunse and fibrous bundles and-multiporous vessels�thenbsp;whole not differing much from the structure of modern Bquiseta.

2. nbsp;nbsp;nbsp;Certain arborescent forms, perhaps allied to the true Calamites,nbsp;as well as possibly the old underground stems of ordinary species,¹nbsp;assumed a thick-walled character in which the tissues resembled thenbsp;wedges of an exogen, and abundance of pseudo-scalariform fibres werenbsp;developed, while the ribbing of the external surface became obsoletenbsp;or was replaced by a mere irregular wrinkling.

3. nbsp;nbsp;nbsp;Sufficient discrimination has not been exercised in separatingnbsp;casts of the internal cavities of Calamites and Calamodendron fromnbsp;those representing other surfaces and the proper external surface.

4. nbsp;nbsp;nbsp;There is no excuse for attributing to Calamites the foliage ofnbsp;Annularia, Asterophyllites, and Sphenophyllum, since these leavesnbsp;have not been found attached to true Calamite stems, and since thenbsp;structure of the stems of Asterophyllites as described by Williamson,nbsp;and that of Sphenophyllum as described by the writer,f are essentially different from those of Calamites.

5. nbsp;nbsp;nbsp;As the species above described indicates, good external characters can be found for establishing species of this genus, and thesenbsp;species are of value as marks of geological age.

This genus has been established to include certain Calamites of the Devonian and Lower Carboniferous, in which the furrows on thenbsp;stem do not alternate at the nodes or joints, and the leaves in onenbsp;species at least bifurcate. C. radiatua, Brongniart, is the typicalnbsp;species. In North America it occurs in the Brian, probably as lownbsp;as the Middle Brian. In Europe it has so far been recognised in thenbsp;Lower Carboniferous only. I have, however, seen stems from allegednbsp;Devonian beds in Devonshire which may have belonged to this species.

Stems ribbed and jointed like the Calamites, but with inflated nodes and a stout internal woody cylinder, which has been describednbsp;by Williamson. Prom the joints proceeded whorls of leaves or ofnbsp;branchlets, bearing leaves which differed from those of Calamites innbsp;their having a distinct middle rib or vein. The fructification con-

Williamson, � Transactions of the Royal Society.� McNab, in �Proceedings of the Edinburgh Botanical Society.�nbsp;f �Journal of the Geological Society,� 1866.

sisted of long slender c�nes or spikes, having whorls of scales bearing the spore-cases. Some authors speak of AaterophyllUes as only branches and leaves of Calamites; but though at first sight the resemblance is great, a close inspection shows that the leaves of As-terophylKtes have a true midrib, which is wanting in Calamites.

Oenus Annularia.�It is perhaps questionable whether these plants should be Separated from Asterophyllites. The distinction isnbsp;that they produce branches in pairs, and that their whorls of leavesnbsp;are one-sided and usually broader than those of Asterophyllites, andnbsp;united into a ring at their insertion on the stem. One little species,nbsp;A. sphenophylloides, is very widely distributed.

PiNNULAEiA�a provisional genus�includes slender roots or stems branching in a pinnate manner, and somewhat irregularly. Theynbsp;are very abundant in the coal shales, and were probably not independent plants, but aquatic roots belonging to some of the plantsnbsp;last mentioned. The probability of this is farther increased by theirnbsp;resemblance in miniature to the roots of Calamites. They are alwaysnbsp;flattened, but seem originally to have been round, with a slendernbsp;thread-like axis of soalariform vessels, enclosed in a soft, smooth,nbsp;cellular bark.

Leaves in whorls, wedge-shaped, with forking veins. Fructification on spikes, with verticils of sporocarps. These plants are by some regarded as allied to the Calamitece and Asterophyllitem, bynbsp;others as a high grade of Rhizocarps of the type of Marsilia. Thenbsp;stem had a star-shaped central bundle of scalariform or reticulato-scalariform vessels.

Under this name we may provisionally include those rounded spherical bodies found in the coal and its accompanying beds, andnbsp;also in the Brian, which may be regarded as Macrospores or Sporocarps of Protosalvinia, or other Rhizocarpean plants akin to those described above in Chapter III, which see for description.

Oenus Protosalvinia.�Under this we include sporocarps allied to those of Salvinia, as described in Chapter III.

Under this head I shall merely refer to a few groups of special interest, and to the provisional arrangement adopted for the frondsnbsp;of ferns when destitute of fructification.

With respect to tree ferns, the oldest known examples are those from the Middle Devonian of New York and Ohio, which I have described in the �Journal of the Geological Society,� 1871 and 1881.nbsp;As these are of some interest, I have reproduced their descriptionsnbsp;in a note appended to Chapter III, which see.

The other forms most frequently occurring in the Carboniferous are Caulopteris, Palmopteris, and Megaphyton* Stems showingnbsp;merely masses of aerial roots are known by the name Psaronius.

With reference to the classification of Palaeozoic ferns, this has hitherto been quite arbitrary, being based on mere form and venation of fronds, but much advance has recently been made in thenbsp;knowledge of their fructification, warranting a more definite attempt at classification. The following are provisional genera usually adopted:

1. nbsp;nbsp;nbsp;Cyclopteria, Brongniart.�Leaflets more or less rounded ornbsp;wedge-shaped, without midrib, the nerves spreading from the pointnbsp;of attachment. This group includes a great variety of fronds evidently of different genera, were their fructification known; and somenbsp;of them probably portions of fronds, the other parts of which maynbsp;be in the next genus.

2. nbsp;nbsp;nbsp;Neuropteris, Brongniart.�Fronds pinnate, and with thenbsp;leaflets narrowed at the base; midrib often not distinct, and disappearing toward the apex. Nervures equal, and rising at an acutenbsp;angle. Ferns of this type are among the most abundant in the coal-formation.

3. nbsp;nbsp;nbsp;Odontopteris, Brongniart.�In these the frond is pinnate, andnbsp;the leaflets are attached by their whole base, with the nerv�es eithernbsp;proceeding wholly from the base, or in part from an indistinct midrib, which soon divides into nervures.

4. nbsp;nbsp;nbsp;Dictyopteris, Gutbier.�This is a beautiful style of fern, withnbsp;leaflets resembling those of Neuropteris, but the veins arranged in anbsp;network of oval spaces. Only a few species are known in the coal-formation.

5. nbsp;nbsp;nbsp;Lonchopteris, Brongniart.�Ferns with netted veins like thenbsp;above, but with a distinct midrib, and the leaflets attached by thenbsp;whole base. Of this, also, we can boast but few species.

6. nbsp;nbsp;nbsp;Sphenopteris, Brongniart.�These are elegant ferns, very numerous in species, and most difflcult to discriminate. Their most

distinctive characters are leaflets narrowed at the base, often lobed, and with nervures dividing in a pinnate manner from the base.

7. nbsp;nbsp;nbsp;Phyllopteris, Brongniart.�These are pinnate, with long lanceolate pinnules, having a strong and well-defined midrib, andnbsp;nerves proceeding from it very obliquely, and dividing as they proceed toward the margin. The ferns of this genus are for the mostnbsp;part found in formations more recent than the Carboniferous; but Inbsp;have referred to it, with some doubt, one of our species.

8. nbsp;nbsp;nbsp;Alethopteris, Brongniart.�This genus includes many of thenbsp;most common coal-formation ferns, especially the ubiquitous A. lon-chitica, which seems to have been the common brake of the coal-formation, corresponding to Pteris aquilina in modern Europe andnbsp;America. These are brake-like ferns, pinnate, with leaflets oftennbsp;long and narrow, deourrent on the petiole, adherent by their wholenbsp;base, and united at base to each other. The midrib is continuous tonbsp;the point, and the nervures run off from it nearly at right angles.nbsp;In some of these ferns the fructification is known to have been marginal, as in Pteris.

9. nbsp;nbsp;nbsp;Pecopteris, Brongniart.�This genus is intermediate betweennbsp;the last and Neuropteris. The leaflets are attached by the wholenbsp;base, but not usually attached to each other; the midrib, thoughnbsp;slender, attains to the summit; the nervures are given off less obliquely than in Neuropteris. This genus includes a large number ofnbsp;our most common fossil ferns.

10. nbsp;nbsp;nbsp;Beinertia, Goeppert.�A genus established by Goeppert for anbsp;curious Peoopteris-like fern, with flexuous branching oblique nervures becoming parallel to the edge of the frond.

11. nbsp;nbsp;nbsp;Hymenophyllites, Goeppert.�These are ferns similar tonbsp;Sphenopteris, but divided at the margin into one-nerved lobes, in thenbsp;manner of the modern genus Hymenophyllum.

13. PaloBopteris, Geinitz.�This is a genus formed to include certain trunks of tree-ferns with oval transverse scars of leaves.

13. nbsp;nbsp;nbsp;Oaulopteris, Bindley and Hutton.�Is another genus of fossilnbsp;trunks of tree-ferns, but with elongate soars of leaves.

14. nbsp;nbsp;nbsp;Psaronius, Cotta.�Includes other trunks of tree-ferns withnbsp;alternate sears or thick scales, and ordinarily with many a�rial rootsnbsp;grouped round them, as in some modern tree-ferns.

15. nbsp;nbsp;nbsp;Megaphytoii, Artis.�Includes trunks of tree-ferns whichnbsp;bore their fronds, which were of great size, in two rows, one on eachnbsp;side of the stem. These were very peculiar trees, less like modernnbsp;ferns than any of the others. My reasons for regarding them asnbsp;ferns are stated in the following extract from a recent paper:

� Their thick stems, marked with linear scars and having two rows of large depressed areoles on the sides, suggest no afSnities tonbsp;any known plants. They are usually ranked with Lepidodendronnbsp;and Ulodendron, but sometimes, and probably with greater reason,nbsp;are regarded as allied to tree-ferns. At the Joggins a very finenbsp;species {M. magnificum) has been found, and at Sydney a smallernbsp;species {M. humile); but both are rare and not well preserved. Ifnbsp;the large scars bore cones and the smaller bore leaves, then, as Bron-gniart remarks, the plant would much resemble Lepidophloios, innbsp;which the cone-scars are thus sometimes distichous. But the soarsnbsp;are not round and marked with radiating scales as in Lepidophloios;nbsp;they are reniform or oval, and resemble those of tree-ferns, for whichnbsp;reason they may be regarded as more probably leaf-soars; and innbsp;that case the smaller linear sears would indicate ramenta, or smallnbsp;aerial roots. Further, the plant described by Corda as Zippea disticha is evidently a Megaphyton, and the structure of that species isnbsp;plainly that of a tree-fern of somewhat peculiar type. On thesenbsp;grounds I incline to the opinion of Geinitz that these curious treesnbsp;were allied to ferns, and bore two rows of large fronds, the trunksnbsp;being covered with coarse hairs or small aerial roots. At one time Inbsp;was disposed to suspect that they may have crept along the ground;nbsp;but a specimen from Sydney shows the leaf-stalks proceeding fromnbsp;the stem at an angle so acute that the stem must, I think, have beennbsp;erect. From the appearance of the scars it is probable that only anbsp;pair of fronds were borne at one time at the top of the stem; and, ifnbsp;these were broad and spreading, it would be a very graceful plant.nbsp;To what extent plants of this type contributed to the accumulationnbsp;of coal I have no means of ascertaining, their tissues in the state ofnbsp;coal not being distinguishable from those of ferns and Lyeo-podiaeece.quot;

16. For descriptions of the genus Archceopteris and other Brian ferns, see Chapter III.

Gbeat physical changes occurred at the close of the Carboniferous age. The thick beds of sediment that hadnbsp;been accumulating in long lines along the primitive continents had weighed down the earth�s crust. Slow subsidence had been proceeding from this cause in the coal-formation period, and at its close vast wrinklings occurred,nbsp;only surpassed by those of the old Laurentian time.nbsp;Hence in the Appalachian region of America we have thenbsp;Carboniferous beds thrown into abrupt folds, their shalesnbsp;converted into hard slates, their sandstones into quartzitenbsp;and their coals into anthracite, and all this before thenbsp;deposition of the Triassic Eed Sandstones which constitute the earliest deposit of the great succeeding Mesozoicnbsp;period. In like manner the coal-fields of Wales andnbsp;elsewhere in western Europe have suffered similar treatment, and apparently at the same time.

This folding is, however, on both sides of the Atlantic limited to a band on the margin of the continents, and tonbsp;certain interior lines of pressure, while in the middle, asnbsp;in Ohio and Illinois in America, and in the great interiornbsp;plains of Europe, the coal-beds are undisturbed and unaltered. In connection with this we have an entirenbsp;change in the physical character of the deposits, a greatnbsp;elevation of the borders of the continents, and probablynbsp;a considerable deepening of the seas, leading to the establishment of general geographical conditions which stillnbsp;remain, though they have been temporarily modified bynbsp;subsequent subsidences and re-elevations.

Along with this a great change was in progress in vegetable and animal life. The flora and fauna of thenbsp;Palseozoic gradually die out in the Permian and are replaced in the succeeding Trias hy those of the Mesozoicnbsp;time. Throughout the Permian, however, the remainsnbsp;of the coal-formation flora continue to exist, and somenbsp;forms, as the Oalamites, even seem to gain in importance,nbsp;as do also certain types of coniferous trees. The Triassic,nbsp;as well as the Permian, was marked by physical disturbances, more especially by great volcanic eruptions discharging vast beds and dykes of lava and layers of volcanicnbsp;ash and agglomerate. This was the case more especiallynbsp;along the margins of the Atlantic, and probably also onnbsp;those of the Pacific. The volcanic sheets and dykes associated with the Bed Sandstones of Nova Scotia, Connecticut, and New Jersey are evidences of this.

At the close of the Permian and beginning of the Trias, in the midst of this transition time of physicalnbsp;disturbance, appear the great reptilian forms characteristic of the age of reptiles, and the earliest precursors ofnbsp;the mammals, and at this time the old Carboniferousnbsp;forms of plants finally pass away, to be replaced by anbsp;flora scarcely more advanced, though different, and consisting of pines, cycads, and ferns, with gigantic equiseta,nbsp;which are the successors of the genus Galamites, a genusnbsp;which still survives in the early Trias. Of these groupsnbsp;the conifers, the ferns, and the equiseta are already familiar to us, and, in so far as they are concerned, a botanistnbsp;who had studied the flora of the Carboniferous wouldnbsp;have found himself at home in the succeeding period.nbsp;The cycads are a new introduction. The whole, however, come within the limits of the cryptogams and thenbsp;gymnosperms, so that here we have no advance.¹

Fontaine�s � Early Mesozoic Flora of Virginia � gives a very good summary of this flora in America.

As we ascend, however, in the Mesozoic, we find new and higher types. Even within the Jurassic epoch, thenbsp;next in succession to the Trias, there are clear indications of the presence of the endogens, in species allied to

the screw-pines and grasses ; and the palms appear a little later, while a few exogenous trees have left theirnbsp;remains in the Lower Cretaceous, and in the Middle andnbsp;Upper Cretaceous these higher plants come in abundantly and in generic forms still extant, so that the dawnnbsp;of the modern fiora belongs to the Middle and Upper

Cretaceous. It will thus be convenient to confine ourselves in this chapter to the flora of the earlier Mesozoic.

Passing over for the present the cryptogamous plants already familiar in older deposits, we may notice the newnbsp;features of gymnospermous and phsenogamous life, as theynbsp;present themselves in this earlier part of the great reptilian age, and as they extended themselves with remarkable uniformity in this period over all parts of the world.nbsp;For it is a remarkable fact that, if we place together innbsp;our collections fossil plants of this period from Australia,nbsp;India, China, Siberia, Europe, or even from Greenland,nbsp;we find wonderfully little difference in their aspect. Thisnbsp;uniformity we have already seen prevailed in the Palaeozoic flora; and it is perhaps equally marked in that ofnbsp;the Mesozoic. Still we must bear in mind that somenbsp;of the plants of these periods, as the ferns and pines,

for example, are still world-wide in theirnbsp;distribution; but thisnbsp;does not apply to others, more especiallynbsp;the cycads (Fig. 65).

The cycads constitute a singular and exceptional type in the modern world, andnbsp;are limited at presentnbsp;to the warmer climates, though verynbsp;generally distributednbsp;in these, as they occur in Africa, India,nbsp;Japan, Australia, Mexico, Florida, and the West Indies.nbsp;In the Mesozoic age, however, they were world-wide innbsp;their distribution, and are found as far north as Greenland, though most of the species found in the Cretaceous

of that country are of small size, and may have been of low growth, so that they may have been protected by thenbsp;snows of winter. The cycads have usually simple or unbranching stems, pinnate leaves borne in a crown at top,nbsp;and fruits which, though somewhat various in structurenbsp;and arrangement, are all of the simpler form of gymno-spermous type. The stems are exogenous in structure,nbsp;but with slender wood and thick bark, and barred tissue,nbsp;or properly as tissue intermediate between this and thenbsp;disc-bearing fibres of the pines.

Though the cycads have a considerable range of organisation and of fructification, and though some points in reference to the latter might assign them a highernbsp;place, on the whole they seem to occupy a lower positionnbsp;than the conifers or the cordaitese of the Carboniferous.nbsp;In the Carboniferous some of the fern-like leaves assignednbsp;to the genus NoeygeratMa have been shown by Stur andnbsp;Weiss to have been gymnosperms, probably allied tonbsp;cycads, of which they may be regarded at least as precursors. Thus the cycadean type does not really constitute an advance in grade of organisation in the Mesozoic,nbsp;any further than that, in the period now in question, itnbsp;becomes much more developed in number and variety ofnbsp;forms. But the conifers would seem to have had precedence of it for a long time in the Palseozoic, and it replacesnbsp;in the Mesozoic the Cordaites, which in many respectsnbsp;excelled it in complexity.

The greater part of the cycads of the Mesozoic age would seem to have had short stems and to have constituted the undergrowth of woods in which conifers attained to greater height. An interesting case of this isnbsp;the celebrated dirt-bed of the quarries of the Isle of Portland, long ago described by Dean Buckland. In thisnbsp;fossil soil trunks of pines, which must have attained tonbsp;great height, are interspersed with the short, thick stemsnbsp;of cycads, of the genus named Cycadoidea by Buckland,

and which from their appearance are called �fossil birds� nests� by the quarrymen. Some, however, mustnbsp;have attained a considerable height so as to resemblenbsp;palms.

The cycads, with their simple, thick trunks, usually marked with rhombic scars, and bearing broad spreadingnbsp;crowns of large, elegantly formed pinnate leaves, mustnbsp;have formed a prominent part of the vegetation of thenbsp;northern hemisphere during the whole of the Mesozoicnbsp;period. A botanist, had there been such a person at thenbsp;time, would have found this to be the case everywherenbsp;from the equator to Spitzbergen, and probably in thenbsp;southern hemisphere as well, and this throughout all thenbsp;long periods from the Early Trias to the Middle Cretaceous. In a paper published in the � Linnsean Transactions� for 1868, Dr. Carruthers enumerates twenty species of British Mesozoic cycads, and the number mightnbsp;now be considerably increased.

The pines present some features of interest. We have already seen their connection with the broad-leaved Cor-daites, and in the Permian there are some additional

types of broad-leaved conifers. In the Mesozoic we have greatnbsp;numbers of beautiful trees,nbsp;with those elegant fan-shapednbsp;leaves characteristic of but onenbsp;living species, the Salisbiiria,nbsp;or gingko-tree of China. , It isnbsp;curious that this tree, thoughnbsp;now limited to eastern Asia,nbsp;will grow, though it rarelynbsp;fruits, in most parts of temperate Europe, and in America as far north as Montreal,nbsp;and that in the Mesozoic period it occupied all these regions, and even Siberia and Greenland, and with manynbsp;and diversified species (Pig. 66).

Salisluria belongs to tbe yews, but an equally curious fact applies to the cypresses. The genus Sequoia, limitednbsp;at present to two species, both Californian, and one ofnbsp;them the so-called �big tree,� celebrated for the giganticnbsp;size to which it attains, is represented by species found asnbsp;far back at least as the Lower Cretaceous, and in everynbsp;part of the northern hemisphere.¹ It seems to havenbsp;thriven in all these regionsnbsp;throughout the Mesozoicnbsp;and early Kainozoic, andnbsp;then to have disappeared,nbsp;leaving only a small remnant to represent it innbsp;modern days. A numbernbsp;of species have been described from the Mesozoicnbsp;and Tertiary, all of themnbsp;closely related to those nownbsp;existing (Pig. 67).

The following notice of these trees is for the mostnbsp;part translated, with somenbsp;modifications and abridgment, from a paper readnbsp;by the late Prof. Heer before the Botanical Sectionnbsp;of the Swiss Natural History Society:

of an Indian of the Cherokee tribe, Sequo Yah, who invented an alphabet without any aid from the outside world of culture, and taught it to his tribe by writing it upon

leaves. This came into general use among the Chero-kees, before the white man had any knowledge of it; and afterward, in 1828, a periodical was published in thisnbsp;character by the missionaries. Sequo Yah was banishednbsp;from his home in Alabama, with the rest of his tribe, andnbsp;settled in Yew Mexico, where he died in 1843.

When Endlicher was preparing his synopsis of the conifers, in 1846, and had established a number of newnbsp;genera. Dr. Jacbon Tschndi, then living with Endlicher,nbsp;brought before his notice this remarkable man, and askednbsp;him to dedicate this red-wooded tree to the memory of anbsp;literary genius so conspicuous among the red men ofnbsp;America. Endlicher consented to do so, and only endeavored to make the name pronounceable by changingnbsp;two of its letters.

Endlicher founded the genus on the redwood of the Americans, Taxodium sempervirens of Lamb; and namednbsp;the species Sequoia sempervirens. These trees form largenbsp;forests in California, which extend along the coast as farnbsp;as Oregon. Trees are there met with of 300 feet in heightnbsp;and 20 feet in diameter. The seeds have been broughtnbsp;to Europe a number of years ago, and we already see innbsp;upper Italy and around the Lake of Geneva, and in England, high trees; but, on the other hand, they have notnbsp;proved successful around Zurich.

In 1852, a second species of Sequoia was discovered in California, which, under the name of big tree, soon attained a considerable celebrity. Lindley described it, innbsp;1853, as WelUngtonia gigantea; and, in the followingnbsp;year, Decaisne and Torrey proved that it belonged tonbsp;Sequoia, and that it accordingly should be called Sequoianbsp;gigantea.

While the Sequoia sempervirens, in spite of the destructiveness of the American lumbermen, still forms large forests along the coast, the Sequoia gigantea is confined to the isolated clumps which are met with inland at

a height of 5^000 to 7,000 feet above sea-level, and are much sought after by tourists as one of the wonders ofnbsp;the country. Reports came to Europe concerning thenbsp;largest of them which were quite fabulous, but we havenbsp;received accurate accounts of them from Prof. Whitney.nbsp;The tallest tree measured by him has a height of 325nbsp;feet, and in the case of one of the trees the number of thenbsp;rings of growth indicated an age of about 1,300 years.nbsp;It had a girth of 50 to 60 feet.

We know only two living species of Sequoia, both of which are confined to California. The one {8. semper-virens) is clothed with erect leaves, arranged in two rows,nbsp;very much like our yew-tree, and bears small, roundnbsp;cones; the other {S. gigantea) has smaller leaves, setnbsp;closely against the branches, giving the tree more the appearance of the cypress. The cones are egg-shaped, andnbsp;much larger. These two types are therefore sharply defined.

Both of these trees have an interesting history. If we go back into the Tertiary, this same genus meets us withnbsp;a long array of s23ecies. Two of these species correspondnbsp;to those living at present: the 8. Langsdorfii to the 8.nbsp;sempervirens, and the 8. Couttsim to the 8. gigantea.¹nbsp;But, while the living species are confined to California, innbsp;the Tertiary they are spread over several quarters of thenbsp;globe.

Let us first consider the Sequoia Langsdorfii. This was first discovered in the lignite of Wetterau, and wasnbsp;described as Taxites langsdorfii. Heer found it in thenbsp;upper Rhone district, and there lay beside the twigsnbsp;the remains of a cone, which showed that the Taxitesnbsp;Langsdorfii of Brongniart belonged to the Californiannbsp;genus Sequoia established by Endlicher. He afterward

found nauch better preserved cones, together with seeds, along with the plants of east Greenland, which fully-confirmed the determination. At Atanekerdluk innbsp;Greenland (about 70� north latitude) this tree is verynbsp;common. The leaves, and also the flowers and numerousnbsp;cones, leave no doubt that it stands very near to thenbsp;modern redwood. It differs from it, however, in having a much larger number of scales in the cone. The treenbsp;is also found in Spitzbergen at nearly 78� north latitude,nbsp;where Nordenskiold has collected, at Cape Lyell, wonderfully preserved branches. Prom this high latitude thenbsp;species can be followed down through the whole of Europe as far as the middle of Italy (at Senegaglia, Gulf ofnbsp;Spezia). In Asia, also, we can follow it to the steppesnbsp;of Kirghisen, to Possiet, and to the coast of the Sea ofnbsp;Japan, and across to Alaska and Sitka. It is recognizednbsp;by Mr. Starkie Gardner as one of the species found innbsp;the Eocene of Mull in the Hebrides.¹ It is thus knownnbsp;in Europe, Asia, and America, from 43� to 78� northnbsp;latitude, while its most nearly related living species, perhaps even descended from it, is now confined to California.

With this S. Langsdorfii, three other Tertiary species are nearly related (iS'. irevifolia, Hr., S. disticha, Hr.,nbsp;and 8. Nordenski'�ldi, Hr.). These have been met with innbsp;Greenland and Spitzbergen, and one of them has latelynbsp;heen found in the United States. Three other species, innbsp;addition to these, have been described by Lesquereux,nbsp;which appear to belong to the group of the 8. Langsdorfii,nbsp;viz., 8. longifolia, Lesq., 8. angustifolia, and 8. acuminata, Lesq. Several species also occur in the Cretaceous and Eocene of Canada.

These species thus answer to the living Sequoia sem-pervirens ; but we can also point to Tertiary represen-

tatives of the S. gigantea. Their leaves are stiff and sharp-pointed, are thinly set round the branches, and lienbsp;forward in the same way: the egg-shaped cones are innbsp;some cases similar.

There are, however, in the early Tertiary six species, which fill up the gap between 8. sempervirens and 8.nbsp;gigayitea. They are the 8. Couttsim, 8. affinis, Lesq.,nbsp;8. imbricata, Hr., 8. siMrica, Hr., 8. Heerii, Lesq., andnbsp;8. Mformis, Lesq. Of these, 8. Couttsiw, Hr., is thenbsp;most common and most important species. It has shortnbsp;leaves, lying along the branch, like 8. gigantea, andnbsp;small, round cones, like 8. Langsdorfii and sempervirens.nbsp;Bovey Tracey in Devonshire has afforded splendid specimens of cones, seeds, and twigs, which have been describednbsp;in the � Philosophical Transactions.� More lately. Countnbsp;Saporta has described specimens of cones and twigs fromnbsp;Armissan. Specimens of this species have also been foundnbsp;in the older Tertiary of Greenland, so that it must havenbsp;had a wide range. It is very like to the American 8.nbsp;affinis, Lesq.

In the Tertiary there have been already found fourteen well-marked species, which thus include representativesnbsp;of the two living types, 8. sempervirens and 8. gigantea.

We can follow this genus still further back. If we go back to the Cretaceous age, we find ten species, of whichnbsp;five occur in the IJrgon of the Lower Cretaceous, two innbsp;the Middle, and three in the Upper Cretaceous. Amongnbsp;these, the Lower Cretaceous exhibits the two types of thenbsp;8equoia sempervirens and 8. gigantea. To the formernbsp;the 8. 8mitJiiana answers, and to the latter, the Reiclien-iachii. Gein. The 8. 8mitliiana stands indeed uncommonly near the 8. Langsdorfii, both in the appearance ofnbsp;the leaves on the twigs and in the shape of the cones.nbsp;These are, howevei�, smaller, and the leaves do not becomenbsp;narrower toward the base. The 8. pectina. Hr., of thenbsp;Upper Cretaceous, has its leaves arranged in two rows, and

presents a similar appearance. The S. BeichenhacMi is a type more distinct from those now living and those innbsp;the Tertiary. It has indeed stiff, pointed leaves, lyingnbsp;forward, but they are arcnate, and the cones are smaller.nbsp;This tree has been known for a long time, and it servesnbsp;in the Cretaceous as a guiding star, which we can follownbsp;from the Urgonian of the Lower Cretaceous up to thenbsp;Cenomanian. It is known in France, Belgium, Bohemia,nbsp;Saxony, Greenland, and Spitzbergen (also in Canada andnbsp;the United States). It has been placed in another genusnbsp;�Geinitzia�but we can recognise, by the help of thenbsp;cones, that it belongs to Sequoia.

Below this, there is found in Greenland a nearly related species, the 8. ambigua, Hr., of which the leaves are shorter and broader, and the cones round and somewhat smaller.

The connecting link between 8. Smithiana and Reich-enbachii is formed by 8. suhulata, Hr., and 8. rigida, Hr., and three species {8. gracilis, Hr., 8. fastigiata andnbsp;8. Gardneriana, Carr.), with leaves lying closely along thenbsp;branch, and which come very near to the Tertiary speciesnbsp;8. Couttsim. We have therefore in the Cretaceous quitenbsp;an array of species, which fill up the gap between the 8.nbsp;sempervirens and gigantm, and show us that the genusnbsp;Sequoia had already attained a great development in thenbsp;Cretaceous. This was still greater in the Tertiary, innbsp;which it also reached its maximum of geographical distribution. Into the present world the two extremes ofnbsp;the genus have alone continued; the numerous speciesnbsp;forming its main body have fallen out in the Tertiary.

If we look still further back, we find in the Jura a great number of conifers, and, among them, we meet innbsp;the genus Pinus with a type which is highly developed,nbsp;and which still survives ; but for Sequoia we have till nownbsp;looked in vain, so that for the present we can not placenbsp;the rise of the genus lower than the Urgonian of the Cre-

taceotis, however remarkable we may think it that in that period it should have developed into so many species ; andnbsp;it is still more surprising that two species already makenbsp;their appearance which approach so near to the livingnbsp;Sequoia sempervirens and S. gigantea.

Altogether, we have become acquainted, up to the present time, with twenty-six species of Sequoia. Fourteen of these species are found in the Arctic zone, andnbsp;have been described and figured in the �Fossil Floranbsp;of the Arctic Regions.� Sequoia has been recognised bynbsp;Ettingshausen even in Australia, but there in the Eocene.

This is, perhaps, the most remarkable record in the whole history of vegetation. The Sequoias are the giantsnbsp;of the conifers, the grandest representatives of the family,nbsp;and the fact that, after spreading over the whole northernnbsp;hemisphere and attaining to more than twenty specificnbsp;forms, their decaying remnant should now be confined tonbsp;one limited region in western America and to two speciesnbsp;constitutes a sad memento of departed greatness.¹ Thenbsp;small remnant of 8. gigantea still, however, towers abovenbsp;all competitors, as eminently the � big trees � ; but, hadnbsp;they and the allied species failed to escape the Tertiarynbsp;continental submergences and the disasters of the glacialnbsp;period, this grand genus would have been to us an extinctnbsp;type. In like manner the survival of the single gingkonbsp;of eastern Asia alone enables us to understand thatnbsp;great series of taxine trees with fern-like leaves of whichnbsp;it is the sole representative.

Besides these peculiar and now rare forms, we have in the Mesozoic many others related closely to existing yews,nbsp;cypresses, pines, and spruces, so that the conifers werenbsp;probably in greater abundance and variety than they arenbsp;at this day.

The writer has shown that much of the material of the great lignite beds of the Canadian Northwest consists of wood of Sequoia of both thenbsp;modern types.

In this period, also, we find the earliest representatives of the endogenous plants. It is true that some plantsnbsp;found in the coal-formation have been doubtfully referred to these, but the earliest certain examples wouldnbsp;seem to be some bamboo-like and screw-pine-like plantsnbsp;occurring in the Jurassic rocks. Some of these are, it isnbsp;true, doubtful forms, but of others there seems to be nonbsp;question. The modern Pandanus or screw-pine of thenbsp;tropical regions, which is not a pine, however, but anbsp;humble relation of the palms, is a stiffiy branching tree,nbsp;of a candelabra-like form, and with tufts of long leavesnbsp;on its branches, and nuts or great hard berries for fruit,nbsp;borne sometimes in large masses, and so protected as tonbsp;admit of their drifting uninjured on the sea. The stemsnbsp;are supported by masses of a�rial roots like those whichnbsp;strengthen the stems of tree-ferns. These structures andnbsp;habits of growth fit the Pandanus for its especial habitatnbsp;on the shores of tropical islands, to which its masses ofnbsp;nuts are drifted by the winds and currents, and on whosenbsp;shores it can establish itself by the aid of its a�rial roots.

Some plants referred to the cycads have proved veritable botanical puzzles. One of these, the Williamsonia gigas of the English oolite, originally discovered by mynbsp;friend Dr. Williamson, and named by him Zamia gigas, anbsp;very tall and beautiful species, found in rocks of this age innbsp;various parts of Europe, has been claimed by Saporta fornbsp;the Endogens, as a plant allied to Pandanus. Somenbsp;other botanists have supposed the flowers and fruits to benbsp;parasites on other plants, like the modern Rafflesia ofnbsp;Sumatra, but it is possible that after all it may prove tonbsp;have been an aberrant cycad.

The tree-palms are not found earlier than the Middle Cretaceous, where we shall notice them in the next chapter. In like manner, though a few Angiosperms occurnbsp;in rocks believed to be Lower or Lower Middle Cretaceousnbsp;in Greenland and the northwest territory of Canada, and

in Virginia, these are merely precursors of those of the Upper Cretaceous, and are not sufficient to redeem thenbsp;earlier Cretaceous from being a period of pines and cycads.

On the whole, this early Mesozoic flora, so far as known to us, has a monotonous and mean appearance.nbsp;It no doubt formed vast forests of tall pines, perhaps resembling the giant Sequoias of California ; but they mustnbsp;for the most part have been dark and dismal woods,nbsp;probably tenanted by few forms of life, for the great reptiles of this age must have preferred the open and sunnynbsp;coasts, and many of them dwelt in the waters. Still wenbsp;must not be too sure of this. The berries and nuts of thenbsp;numerous yews and cycads were capable of affordingnbsp;much food. We know that in this age there were manynbsp;great herbivorous reptiles, like Iguanodon and Hadrosau-rus, some of them fitted by their structure to feed uponnbsp;the leaves and fruits of trees. There were also severalnbsp;kinds of small herbivorous mammals, and much insectnbsp;life, and it is likely that few of the inhabitants of thenbsp;Mesozoic woods have been preserved as fossils. We maynbsp;vet have much to learn of the inhabitants of these forestsnbsp;of ferns, cycads, and pines. We must not forget in thisnbsp;connection that in the present day there are large islands,nbsp;like New Zealand, destitute of mammalia, and having anbsp;flora comparable with that of the Mesozoic in the northernnbsp;hemisphere, though more varied. We have also the remarkable example of Australia, with a much richer floranbsp;than that of the early Mesozoic, yet inhabited only bynbsp;non-placental mammals, like those of the Mesozoic.

The principal legacy that the Mesozoic woods have handed down to our time is in some beds of coal, locallynbsp;important, but of far less extent than those of the Carboniferous period. Still, in America, the Richmond coalfield in Virginia is of this age, and so are the anthracitenbsp;beds of the Queen Charlotte Islands, on the west coast ofnbsp;Canada, and the coal of Brora in Sutherlandshire. Vain-

THE GEOLOGICAL HISTORY OF PLANTS.

able beds of coal, probably of this age, also exist in China, India, and South Africa ; and jet, which is so extensivelynbsp;used for ornament, is principally derived from the carbonised remains of the old Mesozoic pines.

In the next chapter we have to study a revolution in vegetable life most striking and unique, in the advent ofnbsp;the forest-trees of strictly modern types.

NOTE TO CHAPTER V.

I APPEND to this chapter a table showing the plant-bearing series of the Cretaceous and Laramie of North America, from a paper innbsp;� Trans. B. S. C.,� 1885, which see for further details:

It is a remarkable fact in geological chronology that the culmination of the yegetahle kingdom antedates thatnbsp;of the animal. The placental mammals, the highestnbsp;group of the animal kingdom, are not known till the beginning of the Eocene Tertiary. The dicotyledonousnbsp;Angiosperms, which correspondnbsp;to them in the yegetable kingdom, occur far earlier�in thenbsp;beginning of the Upper Cretaceous or close of the Lowernbsp;Cretaceous. The reign of cy-cads and pines holds throughout the Lower Cretaceous, butnbsp;at the close of that age there isnbsp;a sudden incoming of the higher plants, and a proportionatenbsp;decrease, more especially of thenbsp;cycads.

I have already referred to the angiospermous wood supposednbsp;to be Devonian, but I fear tonbsp;rest any conclusion on this isolated fact. Beyond this, the earliest indications ofnbsp;plants of this class have been found in the Lowernbsp;Cretaceous. Many years ago Heer described and figured the leaves of a poplar {Populus primceva) from

the supposed Lower Cretaceous of Kom�, in Greenland (Fig. 68). Two si:)ecies, a StercuUa and a Laurus ornbsp;Salix, occur among fossils described by me in the uppernbsp;part of the Kootanie series of the Eocky Mountains, andnbsp;Fontaine has recently found in the Potomac group ofnbsp;Virginia�believed to be of ISTeocomian age�several angio-spermous species {Sassafras, Menispermites, Sapindus,nbsp;Aralia, Populus, amp;c.) mixed with a rich flora of cycadsnbsp;and pines. These are the early forerunners of the modern angiospermous flora; but so far as known they donbsp;not occur below the Cretaceous, and in its lower portionsnbsp;only very rarely. When, however, we ascend into thenbsp;Upper Cretaceous, whether of Europe or America, therenbsp;is a remarkable incoming of the higher jflants, undernbsp;generic forms similar to those now existing. This is, innbsp;truth, the advent of the modern flora of the temperatenbsp;regions of the earth. A very interesting tabular view ofnbsp;its early distribution is given by Ward, in the �Americannbsp;Journal of Science � for 1884, of which the following is anbsp;synopsis, with slight emendations. I may add that thenbsp;new discoveries made since 1884 would probably tend tonbsp;increase the proportionate number of dicotyledons in thenbsp;newer groups.

Upper white chalk of Europe; Fort Pierre group of America; coal-measures of Nanaimo ?

(Chalk-marl, greensand, and Gault, Niobrara and Dakota groups of America); Dun-vegan group of Canada; Amboy clays ofnbsp;New Jersey.

(Lower greensand and Speeton clay, Wealden and Hastings sands, Kootanie and Queennbsp;Charlotte groups of Canada.)

Thus we have a great and sudden inswarming of the higher plants of modern types at the close of the Lowernbsp;Cretaceous. In relation to this, Saporta, one of the mostnbsp;enthusiastic of evolutionists, is struck hy this phenomenon of the sudden appearance of so many forms, andnbsp;some of them the most highly differentiated of dicotyledonous plants. The early stages of their evolution may,nbsp;he thinks, have been obscure and as yet unobserved, ornbsp;they may have taken place in some separate region, ornbsp;mother country as yet undiscovered, or they may havenbsp;been produced by a rapid and unusual multiplication ofnbsp;flower-haunting insects ! Or it is even conceivable thatnbsp;the apparently sudden elevation of plants may have beennbsp;due to causes still unknown. This last seems, indeed,nbsp;the only certain inference in the case, since, as Saportanbsp;proceeds to say in conclusion : �Whatever hypothesisnbsp;one may prefer, the fact of the rapid multiplication ofnbsp;dicotyledons, and of their simultaneous appearance innbsp;a great number of places in the northern hemisphere atnbsp;the beginning of the Cenomanian epoch, cannot be disputed.� f

The leaves described by Heer, from the Middle Ore-, taceous of Greenland, are those of a poplar (P. primcevd).nbsp;Those which I have described from a corresponding horizon in the Eocky Mountains are a Sterculites {S. vetus-tula), probably allied to the mallows, and an elongatednbsp;leaf, LauropTiyllum (L. crassinerve) (Fig. 69), whichnbsp;may, however, have belonged to a willow rather than anbsp;laurel. These are certainly older than the Dakota group

Including an estimate of Fontaine�s undescribed species, t �Monde des Plantes,� p. 197.

of the United States and the corresponding formations in Canada. On the eastern side of the American continent, in Virginia, the Potomac series is supposed to be

of Lower Cretaceous age, and here Fontaine, asnbsp;already stated, has foundnbsp;an abundant flora of cy-cads, conifers, and ferns,nbsp;with a few angiosperm-ous leaves, which havenbsp;not yet been described.

In the Canadian Rocky Mountains, a few hundreds of feet above thenbsp;beds holding the before-mentioned species, are thenbsp;shales of the Mill Creeknbsp;series, rich in many species of dicotyledonousnbsp;leaves, and corresponding in age with the Dakota group,nbsp;whose fossils have been so well described, first by Heernbsp;and Capellini, and afterward by Lesquereux. We maynbsp;take this Dakota group and the quader-sandstone of Germany as types of the plant-bearing Cenomanian, and maynbsp;notice the forms occurring in them.

In the first place, we recognise here the successors of our old friends, the ferns and the pines, the latter represented by such genera as Taxites, Sequoia, Olyptostrolus,nbsp;GingJco, and even Finns itself. We also have a fewnbsp;cyeads, but not so dominant as in the previous ages.nbsp;The fan-palms are well represented, both in America andnbsp;in the corresponding series in Europe, especially by thenbsp;genus Sabal, which is the characteristic American type ofnbsp;fan-palm, and there is one genus which Saporta regardsnbsp;as intermediate between the fan-palms and the pinnatelynbsp;leaved species. There are also many fragments of stems

and leaves of carices and grasses, so that these plants, now so important to the nourishment of man and his companion animals, were already represented.

Ill

But the great feature of the time was its dicotyledonous forests, and I have only to enumerate the genera supposed to be represented in order to show the richnessnbsp;of the time in plants of this type. It may be necessarynbsp;to explain here that the generic names used are mostlynbsp;based on leaves, and consequently cannot be held as being

absolutely certain, since we know that at present one genus may have considerable variety in its leaves, and, onnbsp;the other hand, that plants of different genera may benbsp;very much alike in their foliage. There is, however, undoubtedly a likeness in plan or type of structure in leavesnbsp;of closely allied plants, and, therefore, if Judiciouslynbsp;studied, they can be determined with at least approximate certainty.¹ More especially we can attain to muchnbsp;certainty when the fruits as well as the leaves are found,nbsp;and when we can obtain specimens of the wood, showingnbsp;its structure. Such corroboration is not wanting, thoughnbsp;unfortunately the leaves of trees are generally foundnbsp;drifted away from the other organs once connected withnbsp;them. In my own experience, however, I have oftennbsp;found determinations of the leaves of trees confirmed bynbsp;the discovery of their fruits or of the structure of theirnbsp;stems. Thus, in the rich cretaceous plant-beds of thenbsp;Dunvegan series we have beech-nuts associated in thenbsp;same beds with leaves referred to Fagus. In the Laramienbsp;beds I determined many years ago nuts of the Trapanbsp;or water-chestnut, and subsequently Lesquereux found,nbsp;in beds in the United States, leaves which he referred tonbsp;the same genus. Later, I found in collections made onnbsp;the Bed Deer River of Canada my fruits and Lesquereux�snbsp;leaves on the same slab. The presence of trees of thenbsp;genera Gary a and Juglans in the same formation was inferred from their leaves, and specimens have since beennbsp;obtained of silicified wood, with the microscopic structurenbsp;of the modern butternut. Still we are willing to admitnbsp;that determinations from leaves alone are liable to doubt.

In the matter of names of fossil leaves, I sympathise very strongly with Dr. hTathorst, of Stockholm, in his

Great allowance has to be made for the variability of leaves of the game species. The modern hazel (O. rostrata) is a case in point. Itsnbsp;leaves, from different parts of the same plant, are so dissimilar in formnbsp;and size that they might readily be regarded as of different species.

objection to the use of modern generic names for mere leaves, and would be quite content to adopt some noncommittal termination, as that of �pliyllum� or �ites�nbsp;suggested by him. I feel, however, that almost as muchnbsp;is taken for granted if a plant is called Corylophyllum ornbsp;Corylites, as if called Corylus. In either case a judgmentnbsp;is expressed as to its afiSnities, which if wrong under thenbsp;one term is wrong under the other; and after so much hasnbsp;been done by so many eminent botanists, it seems inexpedient to change the whole nomenclature for so smallnbsp;and questionable an advantage. I wish it, however, tonbsp;be distinctly understood that plants catalogued on thenbsp;evidence of leaves alone are for the most part referred tonbsp;certain genera on grounds necessarily imperfect, andnbsp;their names are therefore subject to correction, as newnbsp;facts may be obtained.

The more noteworthy modern genera included in the Dakota flora, as catalogued by Lesquereux, are the following : Liquidarribar, the sweet-gum, is represented both innbsp;America and Europe, the leaves resembling those of thenbsp;modern species, but with entire edges, which seems to benbsp;a common peculiarity of Cretaceous foliage.¹ Populusnbsp;(poplar), as already stated, appears very early in Greenland, and continues with increasing number of speciesnbsp;throughout the Cretaceous and Tertiary. Salix (willow)nbsp;appears only a little later and continues. Of the familynbsp;GupuUferm we have Fagus (beech), Quercus (oak), andnbsp;Castanea (chestnut), which appear together in the Dakotanbsp;group and its equivalents. Eruits of some of the speciesnbsp;are known, and also wood showing structure. Betula

With reference to this, something may be learned from the leaves of modern trees. In these, young shoots have leaves often less toothednbsp;and serrated than those of the adult tree. A remarkable instance is thenbsp;Populus grandideniatus of America, the young shoots of which have entire leaves, quite unlike except in venation those of the parent tree, andnbsp;having an aspect very similar to that of the Cretaceous poplars.

(birch) is represented by a few species, and specimens of its peculiar bark are also common. Alnus (alder) appears in one species at least. The genus Platanus (Pig.nbsp;Yl), that of the plane-trees, represented at present by one

European and one American species, has several species in the Cretaceous, though the plane-trees seem to culminate in the early part of the succeeding Eocene, wherenbsp;there are several species with immense leaves. The large

leaves, known as Oredneria, found in the Cenomanian of Europe, and those called Protophyllum (Fig. 73) innbsp;America, appear to be nearer to the plane-trees than tonbsp;any others, though representing an extinct type. Thenbsp;laurels are represented in this age, and the Americannbsp;genus Sassafras, which has now only one species, has notnbsp;one merely but several species in the Cretaceous. Dios-pyros, the persimmon-tree, was also a Cretaceous genus.

The single species of the beautiful Liriodendron, or tulip-tree, is a remnant of a genus which had several Cretaceous species (Figs. 74, 75). The magnolias, still well represented in the American flora, were equally plentiful in tlienbsp;Cretaceous (Fig. 73). The walnut family were well represented by species of Juglans (butternut) and Cary a, ornbsp;hickory. In all, no less than forty-eight genera are present belonging to at least twenty-five families, runningnbsp;through the whole range of the dicotyledonous exogens.nbsp;This is a remarkable result, indicating a sudden profusion

of forms of these plants of a very striking character. It is further to he obserTcd that some of the genera hare

many species in the Cretaceous and dwindle toward the modern. In others the rererse is thenbsp;case�they have expanded in modern times. Innbsp;a number there seems tonbsp;have been little change.

Dr. Hewberry has given, in the � Bulletinnbsp;of the Torrey Botanicalnbsp;Club,� an interestingnbsp;r�sum� of the historynbsp;of the beautiful Lirio-dendron, or tulip-tree,nbsp;which may be taken asnbsp;an example of a genusnbsp;which has gone downnbsp;in importance in thenbsp;course of its geologicalnbsp;history.

�The genus Lirio-dendron, as all botanists know, is represented in the present flora by a single species, � thenbsp;tulip-tree,� which is confined to eastern America, but grows over allnbsp;the area lying betweennbsp;the Lakes and the Gulf,nbsp;the Mississippi and thenbsp;Atlantic. It is a magnificent tree, on the

whole, the finest in our forests. Its cylindrical trunk, sometimes ten feet in diameter, carries it beyond all itsnbsp;associates in size, while the beauty of its glossy, lyreshaped leaves and tuliplike flowers is only surpassed by the flowers andnbsp;foliage of its first cousin, Magnolia grandijlora.

should stand quite alone in the vegetation of the present day excited the wonder of the earlier botanists, but thenbsp;sassafras, the sweet-gum, and the great Sequoias of the farnbsp;West afford similar examples of isolation, and the latternbsp;are still more striking illustrations of solitary grandeur.�nbsp;(Figs. 74 and 75.)

� Three species of Liriodendron are indicated by leaves found in the Amboy clays�Middle Cretaceous�of Newnbsp;Jersey, and others have been obtained from the Dakotanbsp;group in the West, and from the Dpper Cretaceous stratanbsp;of Greenland. Though differing considerably amongnbsp;themselves in size and form, all these have the deep sinusnbsp;of the upper extremity so characteristic of the genus,nbsp;and the nervation is also essentially the same. Hence,nbsp;we must conclude that the genus Liriodendron, now rep-

resented by a single species, was in the Cretaceous age much more largely developed, having many species, andnbsp;those scattered throughout many lands. In the Tertiarynbsp;age the genus continued to exist, but the species seem tonbsp;have been reduced to one, which is hardly to be distinguished from that now living. In many parts of Europenbsp;leaves of the tulip-tree have been found, and it extendednbsp;as far south as Italy. Its presence there was first madenbsp;known by Unger, in his ' Synopsis,� page 232, and in hisnbsp;�Genera et Species,� page 443, where he describes itnbsp;under the name of Liriodendron procaccinii. The genusnbsp;has also been noticed in Europe by Massalongo, Heer, andnbsp;Ettingshausen, and three species have been distinguished.nbsp;All these are, however, so much like the living speciesnbsp;that they should iirobably be united with it. We herenbsp;have a striking illustration of the wide distribution of anbsp;species which has retained its characters both of fruit andnbsp;leaf quite unchanged through long migrations and annbsp;enormous lapse of time.

� In Europe the tulip-tree, like many of its American associates, seems to have been destroyed by the cold ofnbsp;the Ice period, the Mediterranean cutting off its retreat,nbsp;but in America it migrated southward over the southernnbsp;extension of the continent and returned northward againnbsp;with the amelioration of the climate.�

Leaves of Liriodendron have been recognised in the Cretaceous of Greenland, though it is now a tree ofnbsp;the warm temperate region, and Lesquereux describesnbsp;several species from the Dakota group. But the genusnbsp;has not yet been recognised in the Laramie or in thenbsp;Upper Cretaceous of British Columbia. In the papernbsp;above quoted, Newberry describes three new speciesnbsp;from the Amboy clays, one of which he considers identical with a Greenland form referred by Heer to L.nbsp;Meeki of the Dakota group. Thus, if all Lesque-reux�s species are to be accepted, the genus begins

In New Jersey the Amboy clays are referred to the same age with the Dakota beds of the West. In thesenbsp;Dr. Newberry has found a rich flora, including manynbsp;angiosperms. The following is condensed from a preliminary notice in the � Bulletin of the Torrey Botanicalnbsp;Club� :¹

� The flora of the Amboy clays is closely related to that of the Dakota groirp�most of the genera and somenbsp;of the species being identical�so that we may concludenbsp;they were nearly contemporaneous, though the absence innbsp;New Jersey of the Fort Benton and Niobrara groups ofnbsp;the upper Missouri and the apparent synchronism of thenbsp;New Jersey marls and the Pierre group indicate that thenbsp;Dakota is a little the older.

�At least one-third of the species of the Amboy clays seem to be identical with leaves found in the Upper Cretaceous clays of Greenland and Aachen (Aix la Chapelle),nbsp;which not only indicates a chronological parallelism, butnbsp;shows a remarkable and unexpected similarity in the vegetation of these widely separated countries in the middlenbsp;and last half of the Cretaceous age. The botanical character of the flora of the Amboy clays will be seen from thenbsp;following brief synopsis :

�Ferns.�Twelve species, generally similar and in part identical with those described by Ileer from thenbsp;Cretaceous beds of Greenland, and referred to the generanbsp;DicJcsonia, Gleichenia, and Aspidium.

� Cycads.�Two species, probably identical with the forms from Greenland described by Heer under thenbsp;names of Podozamites marginatus and P. tenuinervis.

Moriconia, Brachyphyllum, CunningJiamites, Finns, Sequoia, and others referred by Heer to Jumper us, Libo-cedrus, Frenelopsis, Thuya, and Dammara. Of these, the most abundant and most interesting are Moriconianbsp;cyclotoxon�the most beautiful of conifers�and Gunning-hamites elegans, both of which occur in the Cretaceousnbsp;clays of Aachen, Prussia, and Patoot, Greenland. Thenbsp;Brachyphyllum was a large and strong species, with imbricated cones, eight inches in length.

� The angiosperms form about seventy species, which include three of Magnolia, four of Liriodendron, three ornbsp;four of Salix, three of Celastrophyllum (of which one isnbsp;identical with a Greenland species), one Celastrus (alsonbsp;found in Greenland), four or five Aralias, two Sassafras,nbsp;one Cinnamomum, one Hedera; with leaves that are apparently identical with those described by Heer as belonging to Andromeda, Cissites, Cornus, Dewalquea, Dios-pyros. Eucalyptus, Ficus, Ilex, Juglans, Laurus, Meni-spermites, Myrica, Myrsine, Prunus, Bhamnus, andnbsp;others not yet determined.

� Some of the Aralias had palmately-lobed leaves, nearly a foot in diameter, and two of the tulip-treesnbsp;{Liriodendron) had leaves quite as large as those of thenbsp;living species. One of these had deeply lobed leaves, likenbsp;those of the white oak. Of the other, the leaves resembled those of the recent tulip-tree, but were larger. Bothnbsp;had the peculiar emargination and the nervation of Liriodendron.

�'Among the most interesting plants of the collection are fine species of Bauhinia and Hymenma. Of these,nbsp;the first is represented by a large number of leaves, somenbsp;of which are six or seven inches in diameter. They arenbsp;deeply bilobed, and have the peculiar and characteristicnbsp;form and nervation of the leaves of this genus. Bauhinia is a leguminous genus allied to Cercis, and now in-

habits tropical and warm temperate climates in both hemispheres. Only one species occurs in the Unitednbsp;States, Bauhinia lunarioides, Gray, found by Dr. Bigelow on the Rio Grande.

� Hymenma is another of the leguminosae, and inhabits tropical America. A species of this genus has been found in the Upper Cretaceous of France, but quite different from the one before us, in which the leaves arenbsp;mnch larger, and the leaflets are united in a commonnbsp;petiole, which is winged ; this is a modification not foundnbsp;in the living species, and one which brings it nearer tonbsp;Bauhinia.

� But the most surprising discovery yet made is that of a number of quite large helianthoid flowers, which Inbsp;have called Palmanthus. These are three to four inchesnbsp;in diameter, and exhibit a scaly involucre, enclosing whatnbsp;much resembles a fleshy receptacle with achenia. Fromnbsp;the border of this radiate a number of ray florets, one tonbsp;two inches in length, which are persistent and must havenbsp;been scarious, like those of HeMchrysum. Though thesenbsp;flowers so much resemble those of the composit�, we arenbsp;not yet warranted in asserting that such is certainly theirnbsp;character. In the Jurassic rocks of Europe and Indianbsp;some flowers not very unlike these have been found, whichnbsp;have been named Williamsonia, and referred to cycads bynbsp;Carrutbers. A similar fossil has been found in the Cretaceous rocks of Greenland, and named by Heer Williamsonia cretacea, but he questions the reference of the genusnbsp;to the Cycade�, and agrees with Hathorst in consideringnbsp;all the species of Williamsonia as parasitic flowers, alliednbsp;to Brugmansia or Bafflesia. The Marquis of Saportanbsp;regards them as monocotyledons, similar to Pandanus.nbsp;More specimens of the flowers now exhibited will perhapsnbsp;prove�what we can now only regard as probable�thatnbsp;the Composit�, like the Leguminosw, Magnoliacem, Ce-lastracem, and other highly organised plants, formed part

of the Cretaceous flora. No composite flowers have before been found in the fossil state, and, as these are among the most complex and specialised forms of florescence, itnbsp;has been supposed that they belonged only to the recentnbsp;epoch, where they were the result of a long series of formative changes.�

The above presents some interesting new types not heretofore found in the Middle Cretaceous. More especially the occurrence of large flowers of the compositenbsp;type presents a startling illustration of the early appearance of a very elevated and complex form. Great interestnbsp;also attaches to these Amboy beds, as serving, with thosenbsp;of Aix and Greenland, to show that the margins of thenbsp;Atlantic were occupied with a flora similar to that occurring at the same time in the interior plateau of Northnbsp;America and on the Pacific slope.

The beds at Aix-la-Chapelle are, however, probably somewhat newer than the Dakota or Amboy beds, andnbsp;correspond more nearly in age with those of the Cretaceous coal-field of Vancouver Island, where there is a verynbsp;rich Upper Cretaceous flora, which I have noticed in detail in the � Transactions of the Eoyal Society of Canada.�¹ In these Upj^er Cretaceous beds there are fan-palms as far north at least as the latitude of 49�, indicating a very mild climate at this period. This inference isnbsp;corroborated by the Upper Cretaceous flora of Atan� andnbsp;Patoot in Greenland, as described by Heer.

The dicotyledonous plants above referred to are trees and shrubs. Of the herbaceous exogens of the period wenbsp;know less. Obviously their leaves are less likely to findnbsp;their way into aqueous deposits than the leaves of trees.nbsp;They are, besides, more perishable, and in densely woodednbsp;countries there are comparatively few herbaceous plants.nbsp;I have examined the beds of mud deposited at the mouth

of a woodland streamlet, and have found them stored with the fallen leaves of trees, but it was in vain to search fornbsp;the leaves of herbaceous plants.

The climate of North America and Europe, represented by the Cenomanian vegetation, is not tropical but warmnbsp;temperate ; but the flora was more uniform than at present, indicating a very equable climate and the possibilitynbsp;of temperate genera existing within the Arctic circle, andnbsp;it would seem to have become warmer toward the close ofnbsp;the period.

The flora of the Cenomanian is separated in most countries from that of the Senonian, or uppermost Cretaceous, by a marine formation holding few plants. Thisnbsp;depends on great movements of elevation and depression,nbsp;to which we must refer in the sequel. In a few regions,nbsp;however, as in the vicinity of the Peace River in Canada,nbsp;there are plant-bearing beds which serve to bridge overnbsp;the interval between thenbsp;Early Cenomanian andnbsp;the later Cretaceous.¹

To this interval also would seem to belongnbsp;the Belly River series ofnbsp;western Canada, whichnbsp;contains important bedsnbsp;of coal, but is closely associated with the marinenbsp;Port Pierre series. Anbsp;very curious herbaceous

plant of this group, which I have named Brasenia an-tiqua, occurs in the beds associated with one of the coals. It is a close ally of the modern B. peltata, an aquaticnbsp;plant which occurs in British Columbia and in eastern

See paper by the author in the � Transactions of the Eoyal Society of Canada,� 1882.

America, and is also said to be found in Japan, Australia, and India, a width of distribution appropriate to so oldnbsp;a type (Fig. 76).

In so far as vegetable life is concerned, the transition from the Upper Cretaceous to the Tertiary or Kainozoicnbsp;is easy, though in many parts of the world, and morenbsp;especially in western Europe, there is a great gap in thenbsp;deposits between the upper Chalk and the lowest Eocene.nbsp;With reference to fossil plants, Schimper recognises innbsp;the Kainozoic, beginning with the oldest, five formationsnbsp;�Paleeocene, Eocene, Oligocene, Miocene, and Pliocene.nbsp;Throughout these a flora, similar to that of the Cretaceous on the one hand and the modern on the other,nbsp;though with important local peculiarities, extends. Therenbsp;is evidence, however, of a gradual refrigeration, so thatnbsp;in the Pliocene the climates of the northern hemispherenbsp;were not markedly different from their present character.

In the first instance an important error was committed by palseobotanists, in referring to the Miocene many deposits really belonging to the Eocene. Thisnbsp;arose from the early study of the rich plant-bearingnbsp;Miocene beds of Switzerland, and from the similarity ofnbsp;the flora all the way from the Middle Cretaceous to thenbsp;later Tertiary. The differences are now being workednbsp;out, and we owe to Mr. Starkie Gardner the credit ofnbsp;pointing these out in England, and to the Geologiealnbsp;Survey of Canada that of collecting the material fornbsp;exhibiting them in the more northern part of America.

In the great interior plain of America there rests on the Cretaceous a series of clays and sandstones withnbsp;beds of lignite, some of them eighteen feet in thickness.nbsp;This was formerly known as the lignitic or lignite Tertiary, but more recently as the Laramie series. Thesenbsp;beds were deposited in fresh or brackish water, in annbsp;internal sea or group of lakes and swamps, when thenbsp;continent was lower than at present. They have been

studied both in the United States¹ and Canada; and, though their flora was originally referred by mistake tonbsp;the Miocene, it is now known to be Eocene or Palseocene,nbsp;or even in part a transition group between the latter andnbsp;the Cretaceous. The following remarks, taken chieflynbsp;from recent papers by the author, f will serve to illustratenbsp;this:

On the geological map of Canada the Laramie series, formerly known as the lignitic or lignite Tertiary, occurs, with the exception of a few outliers, in two largenbsp;areas west of the 100th meridian, and separated from eachnbsp;other by a tract of older Cretaceous rocks, over which thenbsp;Laramie beds may have extended, before the later denudation of the region.

The most eastern of these areas, that of the Souris River and Wood Mountain, extends for some distancenbsp;along the United States boundary, between the 102d andnbsp;109th meridians, and reaches northward to about thirtynbsp;miles south of the �elbow� of the South Saskatchewannbsp;River, which is on the parallel of 51� north. In thisnbsp;area the lowest beds of the Laramie are seen to rest onnbsp;those of the Fox Hill group of the Upper Cretaceous,nbsp;and at one point on the west they are overlaid by beds ofnbsp;Miocene Tertiary age, observed by Mr. McConnell, ofnbsp;the Geological Survey, in the Cypress Hills, and referrednbsp;by Cope, on the evidence of mammalian remains, to thenbsp;White River division of the United States geologists,nbsp;which is regarded by them as Lower Miocene. | The agenbsp;of the Laramie beds is thus stratigraphically determinednbsp;to be between the Fox Hill Cretaceous and the Lower

See more especially the elaborate and valuable reports by Lesque-reux and Newberry, and a recent memoir by Ward on �Types of the Laramie Flora,� �Bulletins of the United States Geological Survey,�nbsp;1881

t �Transactions of the Royal Society of Canada,� 1886-�87. t � Report of the Geological Survey of Canada,� 1885.

Miocene. They are also undoubtedly continuous with the Fort Union group of the United States geologists onnbsp;the other side of the international boundary, and theynbsp;contain similar fossil plants. They are divisible into twonbsp;groups�a lower, mostly argillaceous, and to which thenbsp;name of � Bad Lands beds � may be given, from the �badnbsp;lands� of Wood Mountain, where they are well exposed,nbsp;and an upper, partly arenaceous member, which may benbsp;named the Souris River or Porcupine Creek division.nbsp;In the lower division are found reptilian remains of Uppernbsp;Cretaceous type, with some fish remains more nearly akinnbsp;to those of the Eocene.¹ Neither division has as yetnbsp;afforded mammalian remains.

The western area is of still larger dimensions, and extends along the eastern base of the Rocky Mountains from the United States boundary to about the 55th parallel ofnbsp;latitude, and stretches eastward to the 111th meridian.nbsp;In this area, and more especially in its southern part, thenbsp;officers of the Geological Survey of Canada have recognised three divisions, as follows : (1) The Lower Laramienbsp;or St. Mary River series, corresponding in its characternbsp;and fossils to the Lower or Bad Lands division of thenbsp;other area. (2) A middle division, the Willow Creeknbsp;beds, consisting of clays, mostly reddish, and not recognised in the other area. (3) The Upper Laramie ornbsp;Porcupine Hills division, corresponding in fossils, and tonbsp;some extent in mineral character, to the Souris Rivernbsp;beds of the eastern area.

The fossil plants collected by Dr. G. M. Dawson in the eastern area were noticed by the author in an appendix to Dr. Dawson�s report on the 49th parallel, in 1875,nbsp;and a collection subsequently made by Dr. Selwyn wasnbsp;described in the �Report of the Geological Survey ofnbsp;Canada� for 1879-80. Those of the western area, and

especially collections made by myself near Calgary in 1883, and by officers of the Geological Survey in 1884,nbsp;have been described in the �Transactions of the Eoyalnbsp;Society of Canada,� vols. iii. and iv.

In studying these fossil plants, I have found that there is a close correspondence between those of thenbsp;Lower and Upper Laramie in the two areas above referred to respectively, and that the flora of the Lowernbsp;Laramie is somewhat distinct from that of the Upper,nbsp;the former being especially rich in certain aquatic plants,nbsp;and the latter much more copious on the whole, andnbsp;much more rich in remains of forest-trees. This is, however, possibly an effect rather of local conditions than ofnbsp;any considerable change in the flora, since some Uppernbsp;Laramie forms recur as low as the Belly River series of thenbsp;Cretaceous, which is believed on stratigraphical groundsnbsp;to be considerably older than the Lower Laramie.

With reference to the correlation of these beds with those of the United States, some difficulty has arisen fromnbsp;the tendency of palaeobotanists to refer the plants of thenbsp;Upper Laramie to the Miocene age, although in the reports of Mr. Clarence King, the late director of thenbsp;United States Geological Survey, these beds are classed,nbsp;on the evidence of stratigraphy and animal fossils, asnbsp;Upper Cretaceous. More recently, however, and partlynbsp;perhaps in consequence of the views maintained by thenbsp;writer since 1875, some change of opinion has occurred,nbsp;and Dr. Kewberry and Mr. Lesquereux seem now inclined to admit that what in Canada we recognise asnbsp;Upper Laramie is really Eocene, and the Lower Laramienbsp;either Cretaceous or a transition group between this andnbsp;the Eocene. In a recent paper ¹ Dr. Kewberry gives anbsp;Comparative table, in which he correlates the Lower

Laramie with the Upper Cretaceous of VancouTer Island and the Faxoe and Maestricht beds of Europe, while henbsp;regards the Upper Laramie as equivalent to Europeannbsp;Eocene. Except in so far as the equivalence of thenbsp;Lower Laramie and Vancouver Island beds is concerned,nbsp;this corresponds very nearly with the conclusions of thenbsp;writer in a paper published last year ¹�namely, that wenbsp;must either regard the Laramie as a transition Cretaceo-Eocene group, or must institute our line of separation innbsp;the Willow Creek or Middle Laramie division, which has,nbsp;however, as yet afforded no fossil plants. I doubt, however, the equivalence of the Vancouver beds and thenbsp;Lower Laramie, except perhaps in so far as the uppernbsp;member of the former is concerned. I have also to observe that in the latest report of Mr. Lesquereux he stillnbsp;seems to retain in the Miocene certain formations in thenbsp;West, which from their fossil plants I should be inclinednbsp;to regard as Eocene, f

Two ferns occurring in these beds are remarkable as evidence of the persistence of species, and of the peculiarities of their ancient and modern distribution. Onocleanbsp;sensililis, the very common sensitive fern of easternnbsp;America, is extremely abundant in the Laramie beds overnbsp;a great area in the West. Mr. Starkie Gardner and Dr.nbsp;Newberry have also shown that it is identical with thenbsp;Filicites Heiridicus of Forbes, from the early Eocene bedsnbsp;of the Island of Mull, in Scotland. Thus we have anbsp;species once common to Europe and America, but nownbsp;restricted to the latter, and which has continued to existnbsp;over all the vast ages between the Cretaceous and thenbsp;present day. In the Laramie beds I have found asso-

� Transactions of the Royal Society of Canada,� vol. ii. f While these sheets were going through the press I received a verynbsp;valuable report of Mr. Lester F. Ward upon the Laramie of the Unitednbsp;States. I have merely had time to glance at this report, but can see thatnbsp;the views of the author agree closely with those above expressed.

ciated with this species another and more delicate fern, the modern Davallia {Stenloma) tenuifoUa, but this, unlike its companion, no longer occurs in America, hut isnbsp;found in the mountains of Asia. This is a curious illustration of the fact that frail and delicate plants may henbsp;more ancient than the mountains or plains on whichnbsp;they live.

There are also some very interesting and curious facts in connection with the conifers of the Laramie. One ofnbsp;the most common of these is a Thuja or arbor vitae (thenbsp;so-called �cedar� of Canada). The Laramie species hasnbsp;been named T. interrupta by Newberry, hut it approachesnbsp;very closely in its foliage to T. occidentalis, of easternnbsp;Canada, while its fruit resembles that of the westernnbsp;species, T. gigantea.

Still moi�e remarkable are the Sequoias to which we have already referred, but which in the Laramie age seemnbsp;to have been spread over nearly all North America. Thenbsp;fossil species are of two types, representing respectivelynbsp;the modern 8. gigantea and 8. sempervirens, and theirnbsp;wood, as well as that of Thuja, is found in great abundance in the lignites, and also in the form of silicifiednbsp;trunks, and corresponds with that of the recent species.nbsp;The Laramie contains also conifers of the genera Glypto-strobus, Taxodium, and Taxus j and the genus 8alishurianbsp;or gingko�so characteristic of the Jurassic and Cretaceous�is still represented in America as well as in Europenbsp;in the early Eocene.

We have no palms in the Canadian or Scottish Palaeo-cene, though I believe they are found further south. The dicotyledonous trees are richly represented. Perhaps thenbsp;most conspicuous were three species of Platanus, thenbsp;leaves of which sometimes fill the sandstones, and one ofnbsp;which, P. nobilis, Newberry, sometimes attains the gigantic size of a foot or more in diameter of its blade.nbsp;The hazels are represented by a large-leaved species, G.

Macquarii, and by leaves not distinguishable from those of the modern American species, G. Americana and G.nbsp;rostrata. There are also chestnuts and oaks. But thenbsp;poplars and willows are specially abundant, being represented by no less than six species, and it would seemnbsp;that all the modern types of poplar, as indicated by thenbsp;forms and venation of the leaves, existed already in thenbsp;Laramie, and most of them even in the Upper Cretaceous.nbsp;Sassafras is represented by two species, and the beautifulnbsp;group of Viburnum, to which the modern tree-cranberrynbsp;belongs, has several fine species, of some of which bothnbsp;leaves and berries have been found. The hickories andnbsp;butternuts are also present, the horse-chestnut, the Ga-talpa and Sapindus, and some curious leaves which seemnbsp;to indicate the presence of the modern genus SympJioro-carpus, the snow-berry tribe.

The above may suffice to give an idea of the flora of the older Eocene in North America, and I may refer fornbsp;details to the works of Newberry, Lesquereux, and Ward,nbsp;already cited. I must now add that the so-called Miocene of Atanekerdluk, Greenland, is really of the samenbsp;age, as also the � Miocene � of Mull, in Scotland, ofnbsp;Antrim, in Ireland, and of Bovey Tracey, in the south ofnbsp;England, and the Gelinden, or � Heersian � beds, of Belgium, described by Saporta. In comparing the Americannbsp;specimens with the descriptions given by Gardner of thenbsp;leaf-beds at Ardtown, in Mull, we find, as already stated,nbsp;Onoclea sensibilis, common to both. The species ofnbsp;Sequoia, Gingho, Taxus, and Glyptostrobus are also identical or closely allied, and so are many of the dicotyledonous leaves. For example, Platanoides Hebridicus isnbsp;very near to P. nohilis, and Gorylus Macquarrii is common to both formations, as well as Populus Arctica andnbsp;P. Bichardsoni. I may add that ever since 1875-�76,nbsp;when I first studied the Laramie plants, I have maintained their identity with those of the Fort Union group

of the United States, and of the so-called Miocene of McKenzie Eiver and Greenland, and that the whole arenbsp;Paleocene ; and this conclusion has now been confirmednbsp;by the researches of Gardner in England, and by the discovery of true Lower Miocene beds in the Canadian northwest, overlying the Laramie or lignite series.

In a bulletin of the United States Geological Survey (1886), Dr. White has established in the West the continuous stratigraphical succession of the Laramie andnbsp;the Wahsatch Eocene, thus placing the Laramie conformably below the Lower Eocene of that region. Copenbsp;has also described as the Puerta group a series of bedsnbsp;holding vertebrate fossils, and forming a transition fromnbsp;the Laramie to the Wahsatch. White also testifies that anbsp;number of fresh-water mollusks are common to the Wahsatch and the Laramie. This finally settles the positionnbsp;of the Laramie so far as the United States geologists arenbsp;concerned, and shows that the flora is to be regarded asnbsp;Eocene if not Upper Cretaceous, in harmony with whatnbsp;has been all along maintained in Canada. An importantnbsp;r�sum� of the flora has just been issued by Ward in thenbsp;bulletins of the United States Geological Survey (1887).

Before leaving this part of the subject, I would deprecate the remark, which I see occasionally made, that fossil plants are of little value in determining geological horizons in the Cretaceous and Tertiary. I admit that innbsp;these periods some allowance must be made for localnbsp;differences of station, and also that there is a genericnbsp;sameness in the flora of the northern hemisphere, fromnbsp;the Cenomanian to the modern, yet these local differences and general similarity are not of a nature to invalidate inferences as to age. Ko doubt, so long asnbsp;palgeobotanists seemed obliged, in deference to authority,nbsp;and to the results of investigations limited to a few European localities, to group together, without distinction,nbsp;all the floras of the later Cretaceous and earlier Tertiary,

irrespectiye of stratigraphical considerations, the subject lost its geological importance. But, when a good seriesnbsp;has been obtained in any one region of some extent, thenbsp;case becomes different. Though there is still much imperfection in our knowledge of the Cretaceous and Tertiary floras of Canada, I think the work already done isnbsp;sufficient to enable any competent observer to distinguishnbsp;by their fossil plants the Lower, Middle, and Upper Cretaceous, and the latter from the Tertiary ; and, with thenbsp;aid of the work already done by Lesquereux and Newberry in the United States, to refer approximately to itsnbsp;true geological position any group of plants from beds ofnbsp;unknown age in the West.

An important consequence arising from the above statements is that the period of warm climate whichnbsp;enabled a temperate flora to exist in Greenland was thatnbsp;of the later Cretaceous and early Eocene rather than, asnbsp;usually stated, the Miocene. It is also a question admitting of discussion whether the Eocene flora of latitudesnbsp;so different as those of Greenland, Mackenzie River, northwest Canada, and the United States, were strictly contemporaneous, or successive within a long geologicalnbsp;period in which climatal changes were gradually proceeding. The latter statement must apply at least tonbsp;the beginning and close of the period; but the plantsnbsp;themselves have something to say in favour of contemporaneity. The flora of the Laramie is not a tropicalnbsp;but a temperate flora, showing no doubt that a muchnbsp;more equable climate prevailed in the more northernnbsp;parts of America than at present. But this equabilitynbsp;of climate implies the possibility of a great geographicalnbsp;range on the part of plants. Thus it is quite possiblenbsp;and indeed highly probable that in the Laramie age anbsp;somewhat uniform flora extended from the Arctic seasnbsp;through the great central plateau of America far to thenbsp;south, and in like manner along the western coast of

Europe. It is also to be observed that, as Gardner points out, there are some differences indicating a diversity ofnbsp;climate between Greenland and England, and even between Scotland and Ireland and the south of England,nbsp;and we have similar differences, though not stronglynbsp;marked, between the Laramie of northern Canada andnbsp;that of the United States. When all our beds of thisnbsp;age from the Arctic sea to the 49th parallel have beennbsp;ransacked for plants, and when the palmobotanists of thenbsp;United States shall have succeeded in unravelling thenbsp;confusion which now exists between their Laramie andnbsp;the Middle Tertiary, the geologist of the future will benbsp;able to restore with much certainty the distribution ofnbsp;the vast forests which in the early Eocene covered thenbsp;now bare plains of interior America. Further, since thenbsp;break which in western Europe separates the flora of thenbsp;Cretaceous from that of the Eocene does not exist innbsp;America, it will then be possible to trace the successionnbsp;from the Mesozoic flora of the Trias and of the Queennbsp;Charlotte Islands and Kootanie series of the Lower Cretaceous up to the close of the Eocene; and to determine, for America at least, the manner and conditionsnbsp;under which the angiospermous flora of the later Cretaceous succeeded to the pines and cycads which characterised the beginning of the Cretaceous period. In sonbsp;far as Europe is concerned, this may be more difficult,nbsp;since the want of continuity of land from north to southnbsp;seems there to have been fatal to the continuance of somenbsp;plants during changes of climate, and there were alsonbsp;apparently in the Kainozoic period invasions at certainnbsp;times of species from the south and east, which did notnbsp;occur to the same extent in America.

In recent reports on the Tertiary floras of Australia and New Zealand,¹ Ettingshausen holds that the flora of

the Tertiary, as a whole, was of a generalised character; forms now confined to the southern and northern hemispheres respectively being then common to both. Itnbsp;would thus seem that the present geographical diversitiesnbsp;must have largely arisen from the great changes in climate and distribution of land and water in the laternbsp;Tertiary.

The length of our discussion of the early angiosperm-ous flora does not permit us to trace it in detail through the Miocene and Pliocene, but we may notice the connection through these in the next chapter, and may refernbsp;to the magnificent publications of Heer and Lesquereuxnbsp;on the Tertiary floras of Europe and America respectively.

It may be well to begin this chapter with a sketch of the general physical and geological conditions of the period which was characterised by the advent and culmination of the dicotyledonous trees.

In the Jurassic and earliest Cretaceous periods the prevalence, over the whole of the northern hemispherenbsp;and for a long time, of a monotonous assemblage of gym-nospermous and acrogenous plants, implies a uniformnbsp;and mild climate, and facility for intercommunication innbsp;the north. Toward the end of the Jurassic and beginningnbsp;of the Cretaceous, the land of the northern hemisphere wasnbsp;assuming greater dimensions, and the climate probablynbsp;becoming a little less uniform. Before the close of thenbsp;Lower Cretaceous period the dicotyledonous flora seemsnbsp;to have been introduced, under geographical conditionsnbsp;which permitted a warm temperate climate to extend asnbsp;far north as Greenland.

In the Cenomanian or Middle Cretaceous age we find the northern hemisphere tenanted with dicotyledonousnbsp;trees closely allied to those of modern times, though stillnbsp;indicating a climate much warmer than that which atnbsp;present prevails. In this age, extensive but gradual submergence of land is indicated by the prevalence of chalknbsp;and marine limestones over the surface of both continents ; but a circumpolar belt seems to have been maintained, protecting the Atlantic and Pacific basins from

floating ice, and permitting a temperate flora of great richness to prevail far to the north, and especially alongnbsp;the southern margins and extensions of the circumpolarnbsp;land. These seem to have been the physical conditionsnbsp;which terminated the existence of the old Mesozoic floranbsp;and introduced that of the Middle Cretaceous.

As time advanced the quantity of land gradually increased, and the extension of new plains along the older ridges of land was coincident with the deposition of thenbsp;great Laramie series, and with the origination of its peculiar flora, which indicates a mild climate and considerable variety of station in mountain, plain, and swamp,nbsp;as well as in great sheets of shallow and weedy freshnbsp;water.

In the Eocene and Miocene periods, the continents gradually assumed their present form, and the vegetationnbsp;became still more modern in aspect. In that period ofnbsp;the Eocene, however, in which the great nummuliticnbsp;limestones were deposited, a submergence of land occurrednbsp;on the eastern continent which must have assimilated itsnbsp;physical conditions to those of the Middle Cretaceous.nbsp;This great change, affecting materially the flora of Europe, was not equally great in America, which also by thenbsp;north and south extension of its mountain-chains permitted movements of migration not possible in the Oldnbsp;World. From the Eocene downward, the remains ofnbsp;land-animals and plants are found chiefly in lake-basinsnbsp;occupying the existing depressions of the land, thoughnbsp;more extensive than those now remaining. It must alsonbsp;be borne in mind that the great foldings and fractures ofnbsp;the crust of the earth which occurred at the close of thenbsp;Eocene, and to which the final elevation of such rangesnbsp;as the Alps and the Eocky Mountains belongs, permanently modified and moulded the forms of the continents.

These statements raise, however, questions as to the precise equivalence in time of similar floras found in dif-

ferent latitudes. However equable the climate, there must have been some appreciable difference in proceeding from north to south. If, therefore, as seems innbsp;every way probable, the new species of plants originated on the Arctic land and spread themselves southward, this latter process would occur most naturally innbsp;times of gradual refrigeration or of the access of anbsp;more extreme climate�that is, in times of the elevationnbsp;of land in the temperate latitudes, or, conversely, ofnbsp;local depression of land in the Arctic, leading to invasionsnbsp;of northern ice. Hence, the times of the prevalence ofnbsp;particular types of plants in the far north would precedenbsp;those of their extension to the south, and a flora foundnbsp;fossil in Greenland might be supposed to be somewhatnbsp;older than a similar flora when found farther south. Itnbsp;would seem, however, that the time required for the extension of a new flora to its extreme geographical limit isnbsp;so small, in comparison with the duration of an entirenbsp;geological period, that, practically, this difference is ofnbsp;little moment, or at least does not amount to antedatingnbsp;the Arctic flora of a particular type by a whole period,nbsp;but only by a fraction of such period.

It does not appear that, during the whole of the Cretaceous and Eocene periods, there is any evidence of such refrigeration as seriously to interfere with the flora, butnbsp;perhaps the times of most considerable warmth are thosenbsp;of the Dunvegan group in the Middle Cretaceous, andnbsp;those of the later Laramie and oldest Eocene.

It would appear that no cause for the mild temperature of the Cretaceous needs to be invoked, other than those mutations of land and water which the geologicalnbsp;deposits themselves indicate. A condition, for example,nbsp;of the Atlantic basin in which the high land of Greenlandnbsp;should be reduced in elevation, and at the same time thenbsp;northern inlets of the Atlantic closed against the invasionnbsp;of Arctic ice, would at once restore climatic conditions

allowing of the growth of a temperate flora in Greenland. As Dr. Brown has shown,* and as I have elsewherenbsp;argued, the absence of light in the Arctic winter is nonbsp;disadvantage, since, during the winter, the growth ofnbsp;deciduous trees is in any case suspended ; while the constant continuance of light in the summer is, on the contrary, a very great stimulus and advantage.

It is a remarkable phenomenon in the history of genera of plants in the later Mesozoic and Tertiary, that the older genera appear at once in a great number of specificnbsp;types, which become reduced as well as limited in I�angenbsp;down to the modern. This is, no doubt, connected withnbsp;the greater differentiation of local conditions in the modern ; but it indicates also a law of rapid multiplication ofnbsp;species in the early life of genera. The distribution of thenbsp;species of Salisburia, Sequoia, Platanus, Sassafras, Lirio-dendron. Magnolia, and many other genera, affords remarkable proofs of this.

Gray, Saporta, Heer, Newberry, Lesquereux, and Starkie Gardner have all ably discussed these points ; butnbsp;the continual increase of our knowledge of the severalnbsp;floras, and the removal of error as to the dates of theirnbsp;appearance, must greatly conduce to clearer and morenbsp;definite ideas. In particular, the prevailing opinion thatnbsp;the Miocene was the period of the greatest extension ofnbsp;warmth and of a temperate flora into the Arctic, mustnbsp;be abandoned in favour of the later Cretaceous andnbsp;Eocene ; and, if I mistake not, this will be found to accord better with the evidence of general geology and ofnbsp;animal fossils.

In these various revolutions of the later Cretaceous and Kainozoic periods, America, as Dr. Gray has wellnbsp;pointed out, has had the advantage of a continuous stretchnbsp;of high land from north to south, affording a more sure

refuge to plants in times of submergence, and means of escape to the south in times of refrigeration. Hence,nbsp;the greater continuity of American vegetation and thenbsp;survival of genera like Sequoia and Liriodendron, whichnbsp;have perished in the Old World. Still, there are some exceptions to this, for the gingko-tree is a case of survival innbsp;Asia of a type once plentiful in America, hut now extinctnbsp;there. Eastern Asia has had, however, some considerablenbsp;share of the same advantage possessed by America, withnbsp;the addition, referred to by Gray, of a better and morenbsp;insular climate.

But our survey of these physical conditions can not be considered complete till we shall have considered thenbsp;great Glacial age of the Pleistocene. It is certain thatnbsp;throughout the later Miocene and Pliocene the area of landnbsp;in the northern hemisphere was increasing, and the largenbsp;and varied continents were tenanted by the noblest vegetation and the grandest forms of mammalian life that thenbsp;earth has ever witnessed. As the Pliocene drew to anbsp;close, a gradual diminution of warmth came on, andnbsp;more especially a less equable climate, and this was accompanied with a subsidence of the land in the temperatenbsp;regions and with changes of the warm ocean-currents.nbsp;Thus gradually the summers became cooler and thenbsp;winters longer and more severe, the hill-tops becamenbsp;covered with permanent snows, glaciers ploughed theirnbsp;way downward into the plains, and masses and fields ofnbsp;floating ice cooled the seas. In these circumstances thenbsp;richer and more delicate forms of vegetation must havenbsp;been chilled to death or obliged to remove farther south,nbsp;and in many extensive regions, hemmed in by the advancenbsp;of the sea on the one hand and land-ice on the other, theynbsp;must have altogether perished.

Yet even in this time vegetation was not altogether extinct. Along the Gulf of Mexico in America, and innbsp;the Mediterranean basin in Europe, there were still some

remains of a moderate climate and certain boreal and arctic forms moving southward continued to exist herenbsp;and there in somewhat high latitudes, just as similarnbsp;plants now thrive in Grinnell Land within sight of thenbsp;snows of the Greenland mountains. A remarkable summary of some of these facts as they relate to England wasnbsp;given by an eminent English botanist, Mr. Carruthers, innbsp;his address as President of the Biological Section of thenbsp;British Association at Birmingham in 1886. At Cromer,nbsp;on the coast of Norfolk, the celebrated forest-bed of newer Pliocene age, and containing the remains of a copiousnbsp;mammalian fauna, holds also remains of plants in a statenbsp;admitting of determination. These have been collectednbsp;by Mr. Eeid, of the Geological Survey, and were reportednbsp;on by Carruthers, who states that they represent a somewhat colder temperature than that of the present day. Inbsp;quote the following details from the address.

With reference to the plants of the forest-bed or newer Pliocene he remarks as follows :

� Only one species {Trapa natans, Willd.) has disappeared from our islands. Its fruits, which Mr. Eeid found abundantly in one locality, agree with those of thenbsp;plants found until recently in the lakes of Sweden. Fournbsp;species {Prunus speciosa, L., (EnantJie TicJienalii, Sm.,nbsp;Potamogeton pteropliyllus, Sch., and Pinus abies, L.)nbsp;are found at present only in Europe, and a fifth {Potamogeton trichoides, Cham.) extends also to North America ; two species {Peucedamim palustre, Moench, andnbsp;Pinus sylvestris, L.) are found also in Siberia, while sixnbsp;more {Sanguisorba officinalis, L., Rubus fruticosus, L.,nbsp;Cornus sanguinea, L., Euphorbia amygdaloides, L.,nbsp;Quercus robur, L., and Potamogeton crispus, L.) extendnbsp;into western Asia, and two {Fagus sylvatica, L., andnbsp;Alnus glutinosa, L.) are included in the Japanese flora.nbsp;Seven species, while found with the others, enter also intonbsp;the Mediterranean flora, extending to North Africa : these

are Thalictrum minus, L., Thalictrum Jlavum, L., Ranunculus repens, L., Stellaria aquatica. Scop., Corylus avellana, L., Yannichellia palustris, L., and Cladiumnbsp;mariscus, Br. With a similar distribution in the Oldnbsp;World, eight species {Bidens tripartita, L., Myosotisnbsp;ccBspitosa, Schultz, Sumda maritima, Dum., GeratopJiyl-lum demersum, L., Sparganium ramosum, Huds., Pota-mogeton pectinatus, L., Car ex paludosa. Good., and Os-munda regalis, L.) are found also in IS'orth America. Ofnbsp;the remainder, ten species {Nupliar luteum, Sm., Meny-anthes trifoliata, L., SiacJiys palustris, L., Rumex mari-timus, L., Rumex acetosella, L., Betula alba, L., Scirpusnbsp;paucijlorus, Lightf., Taxus haccata, L., and Isoetes la-custris, L.) extend round the north temperate zone, whilenbsp;three {Lycopus europmus, L., Alisma plantago, L., andnbsp;PJiragmites communis, Trin.), having the same distribution in the north, are found also in Australia, and onenbsp;{Hippuris vulgaris, L.) in the south of South America.nbsp;The list is completed by Ranunculus aquatilis, L., distributed over all the temperate regions of the globe, andnbsp;Scirpus lacustris, L., which is found in many tropicalnbsp;regions as well.�

He remarks that these plants, while including species now very widely scattered, present no appreciable changenbsp;of characters.

Above this bed are glacial clays, which hold other species indicating an extremely cold climate. They arenbsp;few in number, only Salix polaris, a thoroughly arcticnbsp;species, and its ally, S. cinerea, L., and a moss, Hypnumnbsp;turgescens. Schimp., no longer found in Britain, but annbsp;Alpine and arctic species. This bed belongs to the beginning of the Glacial period, the deposits of which have asnbsp;yet afforded no plants in England. But plants occur innbsp;post-glacial and upper-glacial beds in different parts ofnbsp;England, to v/hich Oarruthers thus refers :

extended far into temperate regions, was not favorable to vegetable life. But in some localities we have stratifiednbsp;clays with plant-remains later than the Glacial epoch,nbsp;yet indicating that the great cold had not then entirelynbsp;disappeared. In the lacustrine beds at Ilolderness isnbsp;found a small birch {Betula nana, L.), now limited innbsp;Great Britain to some of the mountains of Scotland, butnbsp;found in the arctic regions of the Old and New Worldnbsp;and on Alpine districts in Europe, and with it Prunusnbsp;padus, L., Quercus rdbur, L., Corylus avellana, L.,nbsp;Alnus glutinosa, L., and Finns sylvestris, L. In thenbsp;white clay-beds at Bovey Tracey of the same age therenbsp;occur the leaves of Arctostapliylos uva-ursi, L., threenbsp;species of willow, viz., Salix cinerea, L., S. myrtilloides,nbsp;L., and 8. polaris, Wahl., and in addition to our Alpinenbsp;Betula nana, L., the more familiar B. alba, L. Two ofnbsp;these plants have been lost to our flora from the changenbsp;of climate that has taken place, viz., Salix myrtilloides,nbsp;L., and S. polaris, Wahl.; and Betula nana, L., has retreated to the mountains of Scotland. Three othersnbsp;{Dryas octopetala, L., Arctostapliylos uva-ursi, L., andnbsp;Salix herbacea, L.) have withdrawn to the mountains ofnbsp;northern England, Wales, and Scotland, while the remainder are still found scattered over the country. Notwithstanding the diverse physical conditions to whichnbsp;these plants have been subjected, the remains preservednbsp;in these beds present no characters by which they cannbsp;be distinguished from the living representatives of thenbsp;species.�

One of the instances referred to is very striking. At Bovey Tracey the arctic beds rest directly on those holding the rich, warm temperate flora of the Eocene ; sonbsp;that here we have the evidence of fossil plants to show thenbsp;change from the climate of the Eocene to that of arcticnbsp;lands, and the modern vegetation to indicate the returnnbsp;of a warm temperature.

In Canada, in the Pleistocene beds known as the Leda clays, intervening between the lower boulder clay andnbsp;the Saxicava sand, which also holds boulders, there arenbsp;beds holding fossil plants, in some places intermixed withnbsp;sea-shells and bones of marine fishes, showing that theynbsp;were drifted into the sea at a time of submergence.nbsp;These remains are boreal rather than arctic in character,nbsp;and with the remains of drift-wood often found in thenbsp;boulder deposits serve to indicate that there were at allnbsp;times oases of hardy life in the glacial deserts, just as wenbsp;find these in polar lands at the present day. I condensenbsp;from a paper on these plants ¹ the following facts, with anbsp;few additional notes :

The importance of all information bearing on the temperature of the Post - pliocene period invests withnbsp;much interest the study of the land-plants preserved innbsp;deposits of this age. Unfortunately, these are few in number, and often not well preserved. In Canada, thoughnbsp;fragments of the woody parts of plants occasionally occurnbsp;in the marine clays and sands, there is only one localitynbsp;which has afforded any considerable quantity of remainsnbsp;of their more perishable parts. This is the well-knownnbsp;deposit of Leda clay at Green�s Creek, on the Ottawa,nbsp;celebrated for the perfection in which the skeletons ofnbsp;the capelin and other fishes are preserved in the calcareousnbsp;nodules imbedded in the clay. In similar nodules, contained apparently in a layer somewhat lower than thatnbsp;holding the ichthyolites, remains of land-plants are somewhat abundant, and, from their association with shells ofnbsp;Leda glacialis, seem to have been washed down from thenbsp;land into deep water. The circumstances quot;would seem tonbsp;have been not dissimilar from those at present existingnbsp;in the northeast arm of Gasp� Basin, where I have dredgednbsp;from mud now being deposited in deep water, living

1. nbsp;nbsp;nbsp;Drosera rotundifolia, Linn. In a calcareous nodulenbsp;from Green�s Creek, the leaf only preserved. This plantnbsp;is common in bogs in Canada, Nova Scotia, and Newfoundland, and thence, according to Hooker, to the Arcticnbsp;circle. It is also European.

2. nbsp;nbsp;nbsp;Acer spicatum, Lamx. (Acer montanum, Alton.)nbsp;Leaf in a nodule from Green�s Creek. Found in Novanbsp;Scotia and Canada, also at Lake Winnipeg, according tonbsp;Eichardson.

3. nbsp;nbsp;nbsp;Potentilla Canadensis, Linn. In nodules fromnbsp;Green�s Creek; leaves only preserved. I have had some

difficulty in determining these, but believe they must be referrednbsp;to the species above named, ornbsp;to P. simplex, Michx., supposednbsp;by Hooker and Gray to be a variety. It occurs in Canada andnbsp;New England, but I have no information as to its range northward.

4. Oaylussaccia resinosa, Tor-rey and Gray. Leaf in nodulenbsp;at Green�s Creek. Abundant innbsp;New England and in Canada,nbsp;also on Lake Huron and the Saskatchewan, according tonbsp;Richardson (Fig. 77).

5. Populus halsamifera, Linn. Leaves and branchesnbsp;in nodules at Green�s Creek. This is by much the mostnbsp;common species, and its leaves are of small size, as if fromnbsp;trees growing in cold and exposed situations. The speciesnbsp;is North American and Asiatic, and abounds in New England and Canada. It extends to the Arctic circle, and is

abundant on the shores of the Great Slave Lake and on the McKenzie Eiver, and according to Richardson constitutes much of the drift timber of the Arctic coastnbsp;(Fig. 78). _

6. Thuja occidentalis, Linn. Trunks and branchesnbsp;in the Leda clay at Montreal. This tree occurs in Kewnbsp;England and Canada, and extends northward into the

Hudson Bay territories. It is a northern though not arctic species in its geographical range. According tonbsp;Lyell it occurs associated with the bones of Mastodon innbsp;New Jersey. From the great durability of its wood, it isnbsp;one of the trees most likely to be preserved in aqueousnbsp;deposits.

7. nbsp;nbsp;nbsp;Potamogeton perfoliatus, Linn. Leaves and seedsnbsp;in nodules at Green�s Creek. Inhabits streams of thenbsp;Northern States and Canada, and according to Richardson extends to Great Slave Lake.

8. nbsp;nbsp;nbsp;Potamogeton pusillus. Quantities of fragmentsnbsp;'Which I refer to this species occur in nodules at Green�snbsp;Creek. They may possibly belong to a variety of P.nbsp;hybridus which, together with P. natans, now grows in

9. nbsp;nbsp;nbsp;Caricem and Graminem. Fragments in nodulesnbsp;from Green�s Creek appear to belong to plants of thesenbsp;groups, but I cannot venture to determine their species.

10. nbsp;nbsp;nbsp;Equisetum scirpoides, Michx. Fragments in nodules, Green�s Creek. This is a widely distributed species, occurring in the Northern States and Canada.

11. nbsp;nbsp;nbsp;Fontinalis. In nodules at Green�s Creek therenbsp;occur, somewhat plentifully, branches of a moss apparently of the genus Fontinalis.

12. AlgcB. With thenbsp;plants above mentioned,nbsp;both at Green�s Creeknbsp;and at Montreal, therenbsp;occur remains of seaweeds (Fig. 79). Theynbsp;seem to belong to thenbsp;genera Fucus and Ulva,nbsp;but I cannot determinenbsp;the species. A thicknbsp;stem in one of the nodules would seem to indicate a large Laminaria.nbsp;With the above there arenbsp;found at Green�s Creek anbsp;number of fragments of leaves, stems, and fruits, whichnbsp;I have not been able to refer to their species, principallynbsp;on account of their defective state of preservation.

None of the plants above mentioned is properly arctic in its distribution, and the assemblage may be characterised as a selection from the present Canadian flora of somenbsp;of the more hardy species having the most northernnbsp;range. Green�s Creek is in the central part of Canada,nbsp;near to the parallel of 46�, and an accidental selection

from its jiresent flora^ though it might contain the same species found in the nodules, would certainly include withnbsp;these, or instead of some of them, more southern forms.nbsp;More especially the balsam poplar, though that tree occurs plentifully on the Ottawa, would not be so predominant. But such an assemblage of drift-plants mightnbsp;be furnished by any American stream flowing in the latitude of 50� to 55� north. If a stream flowing to thenbsp;north, it might deposit these plants in still more northernnbsp;latitudes, as the McKenzie Eiver does now. If flowingnbsp;to the south, it might deposit them to the south of 50�.nbsp;In the case of the Ottawa, the plants could not have beennbsp;derived from a more southern locality, nor probably fromnbsp;one very far to the north. We may therefore safely assume that the refrigeration indicated by these plantsnbsp;would place the region bordering the Ottawa in nearly thenbsp;same position with that of the south coast of Labradornbsp;fronting on the Gulf of St. Lawrence at present. Thenbsp;absence of all the more arctic species occurring in Labrador should perhaps induce us to infer a somewhat,nbsp;milder climate than this.

The moderate amount of refrigeration thus required, would in my opinion accord very well with the probablenbsp;conditions of climate deducible from the circumstances innbsp;which the fossil plants in question occur. At the timenbsp;when they were deposited the sea flowed up the Ottawanbsp;valley to a height of 200 to 400 feet above its presentnbsp;level, and the valley of the St. Lawrence was a wide armnbsp;of the sea, open to the arctic current. Under these conditions the immense quantities of drift-ice from thenbsp;northward, and the removal of the great heating surfacenbsp;now presented by the low lands of Canada and New England, must have given for the Ottawa coast of that periodnbsp;a summer temperature very similar to that at present experienced on the Labrador coast, and with this conclusionnbsp;the marine remains of the Leda clay, as well as the few

liind molluscs whose shells have been found in the beds containing the plants, and which are species still occurring in Canada, perfectly coincide.

The climate of that portion of Canada above water at the time when these plants were imbedded may safely henbsp;assumed to have been colder in summer than at present,nbsp;to an extent equal to about 5� of latitude, and this refrigeration may be assumed to correspond with the requirements of the actual geographical changes implied.nbsp;In other words, if Canada was submerged until thenbsp;Ottawa valley was converted into an estuary inhabited bynbsp;species of Leda, and frequented by capelin, the diminution of the summer heat consequent on such depressionnbsp;would be precisely suitable to the plants occurring innbsp;these deposits, without assuming any other cause ofnbsp;change of climate.

I have arranged elsewhere the Post-pliocene deposits of the central part of Canada, as consisting of, in ascending order ; (1) The boulder clay ; (2) a deep-water deposit, the Leda clay ; and (3) a shallow-water deposit, thenbsp;Saxicava sand. But, although I have placed the bouldernbsp;clay in the lowest position, it must be observed that I donbsp;not regard this as a continuous layer of equal age in allnbsp;places. On the contrary, though locally, as at Montreal,nbsp;under the Leda clay, it is in other places and at othernbsp;levels contemporaneous with or newer than that deposit,nbsp;which itself also locally contains boulders.

At Green�s Creek the plant-bearing nodules occur in the lower part of the Leda clay, which contains a fewnbsp;boulders, and is apparently in places overlaid by largenbsp;boulders, while no distinct boulder clay underlies it.nbsp;The circumstances which accumulated the thick bed ofnbsp;boulder clay near Montreal were probably absent in thenbsp;Ottawa valley. In any case we must regard the depositsnbsp;of Green�s Creek as coeval with the Leda clay of Montreal,nbsp;and with the period of the greatest abundance of Leda

glaciaUs, the most exclusively arctic shell of these deposits. In other wordsj I regard the plants above mentioned as probably belonging to the period of greatest refrigeration of which we have any evidence, of course not including that mythical period of universal incasement innbsp;ice, of which, as I have elsewhere endeavoured to show,nbsp;in so far as Canada is concerned, there is no evidencenbsp;wha,tever.¹

The facts above stated in reference to Post-pliocene plants concur, with all the other evidence I have beennbsp;able to obtain, in the conclusion that the refrigeration ofnbsp;Canada in the Post-pliocene period consisted of a diminution of the summer heat, and was of no greater amountnbsp;than that fairly attributable to the great depression of thenbsp;land and the different distribution of the ice-bearingnbsp;arctic current.

In connection with the plants above noticed, it is interesting to observe that at Green�s Creek, at Pakenham Mills, at Montreal, and at Clarenceville on Lake Champlain, species of Canadian Pulmonata have been found innbsp;deposits of the same age with those containing the plants.nbsp;The species which have been noticed belong to the generanbsp;Lymnea and PlanorMs.

The Glacial age was, fortunately, not of very long duration, though its length has been much exaggerated by certain schools of geologists, f It passed away, and a returning cosmic spring gladdened the earth, and was ushered in by a time of great rainfall and consequent denudation and deposit, which has been styled the �� Pluvialnbsp;Period.� The remains of the Pliocene forests then returned�with somewhat diminished numbers of species�

Notes on Post-Pliocene of Canada, �Canadian Naturalist,� IS'72. f This I have long maintained on grounds connected with Pleistocenenbsp;fossils, amount of denudation and deposit, amp;c., and I am glad to see thatnbsp;Prestwich, the best English authority on such subjects, has recently announced similar conclusions, based on independent reasons.

from the south and again occupied the land, though they have not been able, in their decimated condition, to restore the exuberance of the flora of the earlier Tertiary.nbsp;In point of fact, as we shall see in the next chapter, it isnbsp;the floras originating within the polar circle and comingnbsp;down from the north that are rich and copious. Thosenbsp;that, after periods of cold or submergence, return fromnbsp;the south, are comparatively poor. Hence the modernnbsp;flora is far inferior to that of the Middle Kainozoic. Innbsp;America, however, and in eastern Asia, for reasons already stated, the return was more abundant than innbsp;Europe.

Simultaneously with the return of the old temperate flora, the arctic plants that had overspread the land retreated to mountain-tops, now bared of ice and snow, andnbsp;back to the polar lands whence they came ; and so it happens that, on the White Mountains, the Alps, and thenbsp;Himalayas, W'e have insular patches of the same groups ofnbsp;plants that exist around the pole.

These changes need not have required a very long time, for the multiplication and migration of plants arenbsp;very rapid, especially when aided by the agency of migratory animals. Many parts of the land must, indeed, hav^enbsp;been stocked with plants from various sources, and bynbsp;agencies�as that of the sea�which might at first sightnbsp;seem adverse to their distribution. The British Islands,nbsp;for example, have no indigenous plants. Their floranbsp;consists mainly of Germanic plants, which must havenbsp;migrated to Britain in that very late period of the Postglacial when the space now occupied by the North Seanbsp;was mostly dry land. Other portions of it are Scandinavian plants, perhaps survivors of the Glacial age, ornbsp;carried by migratory birds; and still another elementnbsp;consists of Spanish plants, brought north by spring migrants, and establishing themselves in warm and shelterednbsp;spots, just as the arctic plants do on the bleak hill-tops.

The Bermudas, altogether recent islands, have one hundred and fifty species of native plants, all of which are West Indian and American, and must have been introduced by the sea-eurrents or by migratory birds.

And so the earth became fitted for the residence of modern man. Yet it is not so good or Edenic a world asnbsp;it once was, or as it may yet become, were another revolution to restore a mild climate to the arctic regions, andnbsp;to send down a new swarm of migratory sjiecies to renewnbsp;the face of the earth and restore it to its pristine fertilitynbsp;of vegetable life.

Thus closes this long history of the succession of plants, reaching from the far back Laurentian to thenbsp;present day. It has, no doubt, many breaks, and muchnbsp;remains to be discovered. Yet it may lead us to somenbsp;positive conclusions regarding the laws of the introductionnbsp;of plants.

One of these, and perhaps the most remarkable of all, is that certain principles were settled very far back, andnbsp;have remained ever since. We have seen that in thenbsp;earliest geological periods all that pertains to the structure, powers, and laws of the vegetable cell was alreadynbsp;fixed and settled. When we consider how much thisnbsp;implies of mechanical structure and chemical and vitalnbsp;property, the profound significance of this statement becomes apparent. The relations in these respects betweennbsp;the living cell and the soil, the atmosphere and the sunshine, were apparently as perfect in the early Palseozoionbsp;as in any subsequent time.' The same may be said of thenbsp;structures of the leaf and of the stem. In such old formsnbsp;as Nematophylon these were, it is true, peculiar and rudimentary, but in the Devonian and Carboniferous thenbsp;strueture of leaves and stems embodied all the parts andnbsp;principles that we find at present. In regard to fructification there has been more progress, for, so far as wenbsp;know, the highest and most complex forms of flowers.

fruits, and seeds belong to the more recent periods, and simpler forms were at least dominant in the older times.nbsp;Yet even in this respect the great leading laws and structures of bisexual reproduction were perfected in the earlynbsp;PalEeozoic, and the improvements introduced in the gym-nosperm and the angiosperm of later periods have consisted mainly in additions of accessory parts, and in modifications and refinements suited to the wants of the highernbsp;and more complex types.

The origination of the successive floras which have occupied the northern hemisphere in geological time,nbsp;not, as one might at first sight suppose, in the sunnynbsp;climes of the south, hut under the arctic skies, is a factnbsp;long known or suspected. It is proved by the occurrencenbsp;of fossil plants in Greenland, in Spitzbergen, and in Grin-nell Land, under circumstances which show that thesenbsp;were their primal homes. The fact bristles with physicalnbsp;difficulties, yet is fertile of the most interesting theoretical deductions, to reach which we may well be content tonbsp;wade through some intricate questions. Though not atnbsp;all a new fact, its full significance seems only recently tonbsp;have dawned on the minds of geologists, and within thenbsp;last few years it has produced a number of memoirs andnbsp;addresses to learned societies, besides many less formalnbsp;notices.¹

The earliest suggestion on the subject known to the writer is that of Prof. Asa Gray, in 1867, with referencenbsp;to the probable northern source of the related floras ofnbsp;North America and eastern Asia. With the aid. of thenbsp;new facts disclosed by Heer and Lesquereus, Gray re-

Saporta, �Ancienne V�g�tation Polaire�; Hooker, �Presidential Address to Royal Society,� 1878; Thistleton Dyer, �Lecture on Plantnbsp;Distribution�; Mr. Starlde Gardner, �Letters in �Nature,�� 1878, amp;c.nbsp;The basis of most of these brochures is to be found in Heer�s � Floranbsp;Fossilis Arctica.�

turned to the subject in 1872, and more fully developed this conclusion with reference to the Tertiary floras,¹nbsp;and he has recently still further discussed these questionsnbsp;in an able lecture on � Forest Geography and Archeology.� t In this he puts the case so well and tersely thatnbsp;we may quote the following sentences as a text for whatnbsp;follows :

�I can only say, at large, that the same species (of Tertiary fossil plants) have been found all round thenbsp;world ; that the richest and most extensive flnds are innbsp;Greenland ; that they comprise most of the sorts which Inbsp;have spoken of, as American trees which once lived innbsp;Europe�magnolias, sassafras, hickories, gum-trees, ournbsp;identical southern cypress (for all we can see of difference), and especially Sequoias, not only the two whichnbsp;obviously answer to the two big-trees now peculiar tonbsp;California, but several others ; that they equally comprise trees now peculiar to Japan and China, three kindsnbsp;of gingko-trees, for instance, one of them not evidentlynbsp;distinguishable from the Japan species which alone survives ; that we have evidence, not merely of pines andnbsp;maples, poplars, birches, lindens, and whatever else characterise the temperate zone forests of our era, but also ofnbsp;particular species of these, so like those of our own timenbsp;and country that we may fairly reckon them as the ancestors of several of ours. Long genealogies always dealnbsp;more or less in conjecture ; but we appear to be withinnbsp;the limits of scientific inference when we announce thatnbsp;our existing temperate trees came from the north, andnbsp;within the bounds of nigh probability when we claim notnbsp;a few of them as the originals of present species. Eemainsnbsp;of the same plants have been found fossil in our temperate region as well as in Europe.�

Between 1860 and 1870 the writer was engaged in �working out all that could be learned of the Devoniannbsp;plants of eastern America, the oldest known Hora of anynbsp;richness, and which consists almost exclusively of gigantic,nbsp;and to us grotesque, representatives of the club-mosses,nbsp;ferns, and mares�-tails, with some trees allied to the cyeadsnbsp;and pines. In this pursuit nearly all the more importantnbsp;localities were visited, and access was had to the largenbsp;collections of Prof. Hall and Prof. Newberry, in Newnbsp;York and Ohio, and to those made in the remarkablenbsp;plant-bearing beds of New Brunswick by Messrs. Matthewnbsp;and Hartt. In the progress of these researches, whichnbsp;developed an unexpectedly rich assemblage of species, thenbsp;northern origin of this old flora seemed to be establishednbsp;by its earlier culmination in the northeast, in connectionnbsp;w'ith the growth of the American land to the southward,nbsp;which took place after the great Upper Silurian subsidence, by elevations beginning in the north while thosenbsp;portions of the continent to the southwest still remainednbsp;under the sea. The same result was indicated by thenbsp;persistence in the Carboniferous of the south and west ofnbsp;old Brian forms, like Megalopteris.

When, in 1870, the labours of those ten years were brought before the Eoyal Society of London, in thenbsp;Bakerian lecture of that year, and in a memoir illustrating no less than one hundred and twenty-five species ofnbsp;plants older than the great Carboniferous system, thesenbsp;deductions were stated in connection with the conclusionsnbsp;of Hall, Logan, and Dana, as to the distribution of sediment along the northeast side of the American continent,nbsp;and the anticipation was hazarded that the oldest Paleozoic floras would be discovered to the north of Newfoundland. Mention was also made of the ajjparent earliernbsp;and more copious birth of the Devonian flora in Americanbsp;than in Europe, a fact which is itself connected with thenbsp;greater northward extension of this continent.

The memoir containing these results was not published by the Eoyal Society, but its publication was secured in anbsp;less complete form in the reports of the ��Geological Survey of Canada. � The part of the memoir relating to Canadian fossil plants, with a portion of the theoretical deductions, was published in a report issued in 1871.¹ In thisnbsp;report the following language was used :

� In eastern America, from the Carboniferous period onward, the centre of plant distribution has been the Appalachian chain. From this the plants and sedimentsnbsp;extended westward in times of elevation, and to this theynbsp;receded in times of depression. But this centre was nonexistent before the Devonian period, and the centre fornbsp;this must have been to the northeast, whence the greatnbsp;mass of older Appalachian sediment was derived. In thenbsp;Carboniferous period there was also an eastward distribution from the Appalachians, and links of connection innbsp;the Atlantic bed between the floras of Europe and America. In the Devonian such connection can have been onlynbsp;far to the northeast. It is therefore in Newfoundland,nbsp;Labrador, and Greenland that we are to look for thenbsp;oldest American flora, and in like manner on the bordernbsp;of the old Scandinavian nucleus for that of Europe.

�Again, it must have been the wide extension of the sea of the corniferous limestone that gave the last blownbsp;to the remaining flora of the Lower Devonian ; and thenbsp;re-elevation in the middle of that epoch brought in thenbsp;Appalachian ridges as a new centre, and established anbsp;connection with Europe which introduced the Uppernbsp;Devonian and Carboniferous floras. Lastly, from thenbsp;comparative richness of the later Erian f flora in easternnbsp;America, especially in the St. John beds, it might be a

� Fossil Plants of the Devonian and Upper Silurian Formations of Canada,� pp. 92, twenty plates, Montreal, 1871.

fair inference that the northeastern end of the Appalachian ridge was the original birthplace or centre of creation of what we may call the later Palseozoic flora, or of a large part of that flora.�

When my pajDer was written I had not seen the account published by the able Swiss palteobotanist Heer, of the remarkable Devonian flora of Bear Island, near Spitz-bergen.¹ From want of acquaintance with the oldernbsp;floras of America and western Europe, Heer fell into thenbsp;unfortunate error of regarding the whole of Bear Islandnbsp;plants as Lower Carboniferous, a mistake w^hich his greatnbsp;authority has tended to perpetuate, and which has evennbsp;led to the still graver error of some European geologists,nbsp;who do not hesitate to regard as Carboniferous the fossilnbsp;plants of the American deposits from the Hamilton tonbsp;the Chemung groups inclusive, though these belong tonbsp;formations underlying the oldest Carboniferous, and characterised by animal remains of unquestioned Devoniannbsp;age. In 1872 I addressed a note to the Geological Societynbsp;of London on the subject of the so-called � Hrsa stage �nbsp;of Heer, showing that, though it contained some formsnbsp;not known at so early a date in temperate Europe, it wasnbsp;clearly, in part at least, Devonian when tested by Northnbsp;American standards; but that in this high latitude, innbsp;which, for reasons stated in the report above referred to,nbsp;I believed the Devonian plants to have originated, therenbsp;might he an intermixture of the two floras. But such anbsp;mixed group should in that latitude be referred to anbsp;lower horizon than if found in temperate regions. Dr.nbsp;Nathorst, as already stated, has recently obtained newnbsp;facts which go to show that plants of two distinct horizons may have been intermixed in the collections submitted to Heer.

� Transactions of the Swedish Academy,� IStl; � Journal of the London Geological Society,� vol. xxviii.

Between 1870 and 1873 my attention was turned to the two subfloras intermediate between those of the Devonian and the coal-formation, the floras of the Lowernbsp;Carboniferous (Subcarboniferous of some American geologists) and the Millstone Grit, and in a report uponnbsp;these ¹ similar deductions were expressed. It was statednbsp;that in ISTewfoundland the coal-beds seem to belong tonbsp;the Millstone Grit series, and as we proceed southwardnbsp;they belong to progressively newer portions of the Carboniferous system. The same fact is observed in thenbsp;coal-beds of Scotland, as compared with those of England, and it indicates that the coal-formation flora, likenbsp;that of the Devonian, spread itself from the north, andnbsp;this accords with the somewhat extensive occurrence ofnbsp;Lower Carboniferous rocks and fossils in the Parry Islandsnbsp;and elsewhere in the arctic regions.

Passing over the comparatively poor flora of the earlier Mesozoic, consisting largely of cycads, pines, and ferns,nbsp;and as yet little known in the arctic, and which maynbsp;have originated in the south, though represented, according to Heer, by the supposed Jurassic flora of Siberia, wenbsp;find, especially at Kom� and Atan� in Greenland, an interesting occurrence of those earliest precursors of thenbsp;truly modern forms of plants which appear in the Cretaceous, the period of the English chalk and of the Newnbsp;Jersey greensands. There are two plant-groups of thisnbsp;age in Greenland; one, that of Kom�, consists almost entirely of ferns, cycads, and pines, and is of decidedlynbsp;Mesozoic aspect. This is called Lower Cretaceous. Thenbsp;other, that of Atan�, holds remains of many modern temperate genera, as Populus, Myrica, Ficus, Sassafras, andnbsp;Magnolia. This is regarded as Upper Cretaceous. Resting upon these Upper Cretaceous beds, without the inter-

� Fossil Plants of Lower Carboniferous and Millstone Grit Formations of Canada,pp. 47, ten plates, Montreal, 1873.

vention of any other formation,¹ are beds rich in plants of much more modern appearance, and referred hy Heernbsp;to the Miocene period, a reference, as we have seen, notnbsp;warranted by comparison with the Tertiary plants of Europe or of America. Still farther north this so-callednbsp;Miocene assemblage of plants appears in Spitzbergen andnbsp;Grinnell Land ; but there, owing to the predominance ofnbsp;trees allied to the spruces, it has a decidedly more borealnbsp;character than in Greenland, as might be anticipated fromnbsp;its nearer approach to the pole.f

If now we turn to the Cretaceous and Tertiary floras of western America, as described by Lesquereux, Mew-berry, and others, we find in the lowest Cretaceous rochsnbsp;there known�those of the Dakota group�which may benbsp;in the lower part of the Middle Cretaceous, a series ofnbsp;plants X essentially similar to those of the so-called Uppernbsp;Cretaceous of Greenland. They occur in beds indicatingnbsp;land and fresh-water conditions as prevalent at the timenbsp;over great areas of the interior of America. But over-lying this plant-bearing formation we have an oceanicnbsp;limestone (the Niobrara), corresponding in many respectsnbsp;to the European chalk, and extending far north into thenbsp;British territory,¹ indicating that the land of the Lowernbsp;Cretaceous was replaced by a vast Mediterranean Sea,nbsp;filled with warm water from the equatorial currents, andnbsp;not invaded by cold waters from the north. This is succeeded by thick Upper Cretaceous deposits of clay andnbsp;sandstone, with marine remains, though very sparsely

nbsp;nbsp;nbsp;Nordenskiold, � Expedition to Greenland,� � Geological Magazine,�nbsp;1872.

t Yet even here the bald cypress {Taxodium disticimm), or a tree nearly allied to it, is found, though this species is now limited to thenbsp;Southern States. Fielden and De Ranee, � Journal of the Geological Society,� 1878.

distributed; aud these show that further subsidence or denudation in the north had opened a way for the arcticnbsp;currents, killing out the warm-water animals of the Niobrara group, and filling up the Mediterranean of thatnbsp;period. Of the flora of these Upper Cretaceous periods,nbsp;which must have been very long, we know something innbsp;the interior regions, from the discovery of a somewhatnbsp;rich flora in the Dunvegan beds of the Peace Eiver district, on the northern shore of the great Cretaceous Mediterranean and on the coast of British Columbia wenbsp;have the remarkable Cretaceous coal-field of Vancouvernbsp;Island, which holds the remains of plants of modernnbsp;genera, and, indeed, of almost as modern aspect as thosenbsp;of the so-called Miocene of Greenland. They indicate,nbsp;however, a warmer climate as then prevalent on the Pacific coast, and in this respect correspond with a peculiarnbsp;transition flora, intermediate between the Cretaceous andnbsp;Eocene or earliest Tertiary of the interior regions, andnbsp;which is described by Lesquereux as the Lower Lig-nitic.

Immediately above these Upper Cretaceous beds we have the great Lignite Tertiary of the West�the Laramienbsp;group of recent American reports�abounding in fossilnbsp;plants, at one time regarded as Miocene, but now knownnbsp;to be Lower Eocene, though farther south extending upward toward the Miocene age.f These beds, with theirnbsp;characteristic plants, have been traced into the Britishnbsp;territory north of the forty-ninth parallel, and it has beennbsp;shown that their fossils are identical with those of the

* � Reports of Dr. G. M. Dawson, Geological Survey of Canada.� Also, � Transactions of the Royal Society of Canada,� vol. i.

f Lesquereux�s �Tertiary Flora�; �White on the Laramie Group�; Stevenson, � Geological Relations of Lignitie Groups,� American Philosophical Society, June, 18Y6; Dawson, �Transactions of the Royal Society of Canada,� vol. iv.; Ward, � Bulletin of United States Geologicalnbsp;Survey.�

McKenzie Eiver valley, described by Heer as Miocene, and probably also with those of Alaska, referred to thenbsp;same age.¹ Now this truly Eocene flora of the temperatenbsp;and northern parts of America has so many species innbsp;common with that called Miocene in Greenland that itsnbsp;identity can scarcely be doubted. These facts have lednbsp;to scepticism as to the Miocene age of the upper plantbearing beds of Greenland, and more especially Mr. J.nbsp;Starkie Gardner has ably argued, from comparison withnbsp;the Eocene flora of England and other considerations,nbsp;that they are really of that earlier date, f

In looking at this question, we may fairly assume that no climate, however equable, could permit the vegetation of the neighbourhood of Disco in Greenland to benbsp;exactly identical with that of Colorado and Missouri, at anbsp;time when little difference of level existed in the twonbsp;regions. Either the southern flora migrated north innbsp;consequence of a greater amelioration of climate, or thenbsp;northern flora moved southward as the climate becamenbsp;colder. The same argument, as Gardner has ably shown,nbsp;applies to the similarity of the Tertiary plants of temperate Europe to those of Greenland. If Greenland requirednbsp;a temperature of about 50�, as Heer calculates, to maintain its Eocene flora, the temperature of England andnbsp;that of the Southwestern States must have been higher,nbsp;though probably more equable, than at present.

We cannot certainly aflSrm anything respecting the migrations of these floras, but there are some probabilitiesnbsp;which deserve attention. The ferns and cycads of thenbsp;so-called Lower Cretaceous of Greenland are nothing butnbsp;a continuation of the previous Jurassic flora. Now thisnbsp;was established at an equally early date in the Queen

G. M. Dawson, � Report on the Geology of the Forty-ninth Parallel,� where full details on these points may be found. � Transactions of thenbsp;Royal Society of Canada,� vol. iv.

Charlotte Islands,¹ and still earlier in Virginia.f The � presumption is, therefore, that it came from the south.nbsp;It has, indeed, the facies of a southern hemisphere andnbsp;insular flora, and probably spread itself northward as farnbsp;as Greenland, at a time when our northern continentsnbsp;were groups of islands, and when the ocean currents werenbsp;carrying warm water far toward the arctic regions. Thenbsp;flora which succeeds this in the sections at Atan� has nonbsp;special affinities with the southern hemisphere, and is ofnbsp;a more temperate and continental character. J It is notnbsp;necessarily Upper Cretaceous, since it is similar to thatnbsp;of the Dakota group farther south, and this is at leastnbsp;Middle Cretaceous. This flora must have originatednbsp;either somewhere in temperate America or within thenbsp;Arctic circle, and it must have replaced the older one bynbsp;virtue of increasing coolness and continental character ofnbsp;climate. It must, therefore, have been connected withnbsp;that elevation of the land which took place at the beginning of the Cretaceous. During this elevation it spreadnbsp;over all western America at one time or another, and, asnbsp;the land again subsided under the sea of the Niobraranbsp;chalk, it assumed an aspect more suited to a warm climate, but still held its place on such islands as remainednbsp;above water along the Pacific coast and in the north, andnbsp;it continued to exist on these islands till the colder seas

� Reports of the Geological Survey of Canada.� f Fontaine has well described the Mesozoic flora of Virginia, �American Journal of Science,� January, 18Y9, and �Report on Early Mesozoicnbsp;Floras.�

X In the � Proceedings of the Royal Society of Tasmania,� 1887, Mr. R. M. Johnston, F. L. S., states that in the Miocene beds of Tasmania treesnbsp;of European genera abound. The Mesozoic flora of that island is of thenbsp;usual conifero-cycadean type. Ettingshausen makes a similar statementnbsp;in the � Geological Magazine � respecting the Tertiary flora of Australianbsp;and New Zealand, stating that, like the Tertiary floras of Europe, theynbsp;have a mixed character, being partly of types now belonging to the northern hemisphere.

of the Upper Cretaceous had again given place to the warm plains and land-locked brackish seas or fresh-waternbsp;lakes of the Laramie period (Eocene). Thus the truenbsp;Upper Cretaceous marks a cool period intervening between the so-called Upper Cretaceous (really Middle Cretaceous) and the so-called Miocene (really Lower Eocene)nbsp;floras of Greenland.

This latter established itself in Greenland, and probably all around the Arctic circle, in the warm period of the earliest Eocene, and, as the climate of the northernnbsp;hemisphere became gradually reduced from that time tillnbsp;the end of the Pliocene, it marched on over both continents to the southward, chased behind by the modernnbsp;arctic flora, and eventually by the frost and snow of thenbsp;Glacial age. This history may admit of correction in details ; but, so far as present knowledge extends, it is innbsp;the main not far from the truth.

Perhaps the first great question which it raises is that as to the causes of the alternations of warm and cold climates in the north, apparently demanded by the vicissitudes of the vegetable kingdom. Here we may set asidenbsp;the idea that in former times plants were suited to endurenbsp;greater cold than at present. It is true that some of thenbsp;fossil Greenland plants are of unknown genera, and manynbsp;are species new to us; but we are on the whole safe innbsp;affirming that they must have required conditions similarnbsp;to those necessary to their modern representatives, exceptnbsp;within such limits as we now find to hold in similar casesnbsp;among existing plants. Still we know that at the presentnbsp;time many species found in the equable climate of England will not live in Canada, though species to all appearance similar in structure are native here. There is alsonbsp;some reason to suppose that species when new may havenbsp;greater hardiness and adaptability than when in old agenbsp;and verging toward extinction. In any case these factsnbsp;can account for but a small part of the phenomena, which

require to be explained by physical changes affecting the earth as a whole, or at least the northern hemisphere.nbsp;Many theoretical yiews haye been suggested on this subject, and perhaps the most practical way of disposing ofnbsp;these will be first to set aside a number which are eithernbsp;precluded by the known facts, incapable of producingnbsp;the effects, or altogether uncertain as to their possiblenbsp;occurrence.

1. nbsp;nbsp;nbsp;In this class we may place the theory that the polesnbsp;of the earth haye changed their position. Independentlynbsp;of astronomical objections, there is good geological eyi-dence that the poles of the earth must haye been nearlynbsp;in their present places from the dawn of life until now.nbsp;From the Laurentian upward, those organic limestonesnbsp;which mark the areas where warm and shallow equatorialnbsp;water was spreading oyer submerged continents are sonbsp;disposed as to proye the permanence of the poles. Innbsp;like manner all the great foldings of the crust of the earthnbsp;haye followed lines which are parts of great circles tangentnbsp;to the existing polar circles. So, also, from the Cambriannbsp;age the great drift of sediment from the north has followed the line of the existing Arctic currents from thenbsp;northeast to the southwest, throwing itself, for example,nbsp;along the line of the Appalachian uplifts in easternnbsp;America, and against the ridge of the Cordilleras in thenbsp;west.

2. nbsp;nbsp;nbsp;Some of the above considerations, along with astronomical evidence, prevent us from assuming any considerable change in the obliquity of the axis of the earthnbsp;during geological time.

3. nbsp;nbsp;nbsp;That the earth and the sun have diminished innbsp;heat during geological time seems probable ; but physicalnbsp;and geological facts alike render it certain that this influence could have produced no appreciable effect, even innbsp;the times of the earliest floras, and certainly not in thenbsp;case of Tertiary vegetation.

4. nbsp;nbsp;nbsp;It has been supposed that the earth may have atnbsp;different times traversed more or less heated zones ofnbsp;space, giving alternations of warm and cold temperature.nbsp;No such differences in space are, however, known, nornbsp;does there seem any good ground for imagining their existence.

5. nbsp;nbsp;nbsp;The heat of the sun is known to be variable, andnbsp;the eleven years� period of sun-spots has recently attractednbsp;much attention as producing appreciable effects on thenbsp;seasons. There may possibly be longer cycles of solarnbsp;energy, or the sun may be liable, like some variable stars,nbsp;to paroxysms of increased energy. Such changes arenbsp;possible, and may fairly be taken into the account, provided that we fail to find known causes sufficient to account for the phenomena.

Of well-known causes there seem to be but three. These are : First, that urged by Lyell�viz., the varyingnbsp;distribution of land and water along with that of marinenbsp;currents; secondly, the varying eccentricity of the earth�snbsp;orbit, along with the precession of the equinoxes, and thenbsp;effects of this on oceanic circulation, as illustrated bynbsp;Croll; thirdly, the different conditions of the earth�snbsp;atmosphere with reference to radiation, as argued by Tyndall and Hunt. As these causes are all founded on knownnbsp;facts, and not exclusive of each other, we may considernbsp;them together. I shall take the Lyellian theory first, regarding it as the most important, and the best supportednbsp;by geological facts.

We know that the present distribution of land and water greatly influences climate, more especially by affecting that of the ocean currents and of the winds, andnbsp;by the different action of land as compared with water innbsp;the reception and radiation of heat. The present distribution of land gives a large predominance to the arcticnbsp;and sub-arctic regions, as compared with the equatorialnbsp;and with the antarctic; and we might readily imagine

other distributions that would give very dilferent results. But this is not an imaginary case. We know that, whilenbsp;the forms and positions of the great continents have beennbsp;fixed from a very early date, they have experienced manynbsp;great submergences and re-elevations, and that these havenbsp;occurred in somewhat regular sequence, as evidenced bynbsp;the cyclical alternations of organic limestones and earthynbsp;sediments in successive geological formations.

An example bearing on our present subject may serve to illustrate this. In the latter part of the Upper Silurian period (the Lower Helderberg age), vast areas of thenbsp;American continent¹ were covered with an ocean innbsp;which were deposited organic limestones whose fossilsnbsp;show that this great interior sea was pervaded by equatorial waters bringing food and warmth, while the incipient ranges of the Appalachians on the east, and thenbsp;Cordilleras on the west, and the Laurentian axis on thenbsp;north, fenced off from it the colder arctic waters. Hownbsp;different must the climate of America and of the regionnbsp;north of it have been in these circumstances from thatnbsp;which prevails at present, or from that which prevailednbsp;in certain other periods, when it was open to the incursions of the arctic ice-laden currents, bearing loads of finenbsp;sediment ! f It was in these circumstances, and in thenbsp;similar circumstances in which the great Corniferousnbsp;limestone of the Devonian was deposited�a limestonenbsp;showing in its rich coral fauna even warmer waters thannbsp;those of the Lower Helderberg�that the Devonian flora

See a memoir and map by Prof. Hall, � Reports of the Regents of New York,� ISff-�l�.

t It seems certain that the faunte of the old limestones, like the Trenton, Niagara, Lower Helderberg, and Corniferous, belong to warm and sheltered sea areas, and that those rich in graptolites and trilobites, enclosed in muddy sediments, belong to the colder arctic waters. Suchnbsp;arctic faunae are those of the Quebec group and of the Utica shale, andnbsp;to some extent that of the Hamilton group.

took its origin in the north and advanced southward over new lands in process of emergence from the sea. Thenbsp;somewhat similar condition evidenced by the Lower Carboniferous limestone preceded the advent of the great andnbsp;rich flora of the coal-formation.

Lyell�s theory on this subject has, I think, in some recent publications, been somewhat misapprehended. It is true that he stated hypothetically two contrasted conditions of distribution, in one of which all the land wasnbsp;equatorial, in another all polar ; but he did not supposenbsp;that these conditions had actually occurred; and even innbsp;his earlier editions, before the recent discoveries and discussions as to ocean currents, he was always careful to attach due value to these in connection with subsidencesnbsp;and elevations.¹ In his later editions he introducednbsp;more full references to current action, and also statednbsp;Oroll�s theory, but still maintained the validity of hisnbsp;original conclusions.

The sufficiency of this Lyellian theory to account for the facts, in so far as plants are concerned, may, I think,nbsp;be inferred from the course of the isothermal lines atnbsp;present. The south end of Greenland is on the latitudenbsp;of Christiania in Norway on the one hand, and of Fortnbsp;Liard in the Peace Eiver region on the other; and whilenbsp;Greenland is clad in ice and snow, wheat and other grains,nbsp;and the ordinary trees of temperate climates, grow at thenbsp;latter places, f It is evident, therefore, that only exceptionally unfavourable circumstances prevent the Greenlandnbsp;area from still possessing a temperate flora, and these unfavourable circumstances possibly tell even on the localities with which we have compared it. Further, thenbsp;mouth of the McKenzie River is in the same latitude with

See � Principles of Geology,� edition of 1840, chapter vii. f See � Macoun�s Report,� � Geological Survey of Canada,� and Richardson�s � Boat Voyage.�

Disco, near which are some of the most celebrated localities of fossil Cretaceous and Tertiary plants. Yet the mouth of the McKenzie River enjoys a much more favourable climate and has a much more abundant flora thannbsp;Disco. If north Greenland were submerged, and lownbsp;land reaching to the south terminated at Disco, and ifnbsp;from any cause either the cold currents of Baffin�s Baynbsp;were arrested, or additional warm water thrown into thenbsp;Korth Atlantic by the Gulf Stream, there is nothing tonbsp;prevent a mean temperature of 45� Fahr. from prevailingnbsp;at Disco; and the estimate ordinarily formed of the requirements of its extinct floras is 50�,¹ which is probablynbsp;above rather than below the actual temperature required.

Since, then, geological facts assure us of mutations of the continents much greater than those apparently required to account for the changes of climate implied innbsp;the existence of the ancient arctic floras, it does not seemnbsp;absolutely necessary to invoke any others, f If, however,nbsp;there are other true causes which might either aid ornbsp;counteract those above referred to, it may be well tonbsp;consider them.

Mr. Croll has, in his valuable work � Climate and Time,� and in various memoirs, brought forward an ingenious astronomical theory to account for changes ofnbsp;climate. This theory, as stated by himself in a recentnbsp;paper,! is that when the eccentricity of the earth�s orbitnbsp;is at a high value, and the northern winter solstice is innbsp;perihelion, agencies are brought into operation whichnbsp;make the southeast trade-winds stronger than the northeast, and compel them to blow over npon the northern

Heer. See, also, papers by Prof. Ilaughton and by Gardner in � Nature� for 1878.

f Sir William Thomson, � Transactions of the Geological Society of Glasgow,� February 22, 1878.

J � Cataclysmic Theories of Geological Climate,� � Geological Magazine,� May, 1878.

hemisphere as far as the Tropic of Cancer. The result is that all the great equatorial currents of the ocean are impelled into the northern hemisphere, which thus, in consequence of the immense accumulation of warm water,nbsp;has its temperature raised, so that ice and snow must to anbsp;great extent disappear from the arctic regions. In thenbsp;prevalence of the converse conditions, the arctic zone becomes clad in ice, and the southern has its temperaturenbsp;raised.

At the same time, according to Croll�s calculations, the accumulation of ice on either pole would tend, bynbsp;shifting the earth�s centre of gravity, to raise the level ofnbsp;the ocean and submerge the land on the colder hemisphere.nbsp;Thus a submergence of land would coincide with a coldnbsp;condition, and emergence with increasing warmth. Factsnbsp;already referred to, however, show that this has not always been the case, but that in many cases submergencenbsp;was accompanied with the influx of warm equatorialnbsp;waters and a raised temperature, this apparently depending on the question of local distribution of land andnbsp;water ; and this in its turn being regulated not always bynbsp;mere shifting of the centre of gravity, but by foldings occasioned by contraction, by equatorial subsidences resultingnbsp;from the retardation of the earth�s rotation, and by the excess of material abstracted by ice and frost from the arcticnbsp;regions, and drifted southward along the lines of arcticnbsp;currents. This drifting must in all geological times havenbsp;greatly exceeded, as it certainly does at present, the denudation caused by atmospheric action at the equator,nbsp;and must have tended to increase the disposition to equatorial collapse occasioned by retardation of rotation.¹

Croll, in � Climate and Time,� and in a note read before the British Association in 1876, takes an opposite Tiew; but this is clearly contrarynbsp;to the facts of sedimentation, which show a steady movement of debrisnbsp;toward the south and southwest.

tend to reduce the practical importance of Mr. Croll�s theory, on the other hand they tend to remoye one of thenbsp;greatest objections against it�namely, that founded onnbsp;the necessity of supposing that glacial periods recur withnbsp;astronomical regularity in geological time. They cannotnbsp;do so if dependent on other causes inherent in the earthnbsp;itself, and producing important movements of its crust.

The third great cause of warmer climates in the past is the larger proportion of carbon dioxide, or carbonic-acid gas, in the atmosphere in early geological times, asnbsp;proved by the immense amount of carbon now sealed up innbsp;limestone and coal, and which must at one time have beennbsp;in the air. It has been shown that a very small additionalnbsp;quantity of this substance would so obstruct radiation ofnbsp;heat from the earth as to act almost like a glass roof. If,nbsp;however, the quantity of carbonic acid, great at first, wasnbsp;slowly and regularly removed, even if, as suggested bynbsp;Hunt, small additional supplies were gradually addednbsp;from space, this cause could have affected only the verynbsp;oldest floras. But it is known that some comets andnbsp;meteorites contain carbonaceous matter, and this allowsnbsp;us to suppose that accessions of carbon may have beennbsp;communicated at irregular intervals. If so, there maynbsp;have been cycles of greater and less abundance of thisnbsp;substance, and an atmosphere rich in carbon dioxidenbsp;might at one and the same time afford warmth and abund-dance of food to plants.

It thus appears that the causes of ancient vicissitudes of climate are somewhat complex, and when two or morenbsp;of them happened to coincide very extreme changes mightnbsp;result, having most important bearings on the distribution of plants.

This may help us to deal with the peculiarities of the great Glacial age, which may have been rendered exceptionally severe by the combination of several of the causesnbsp;of refrigeration. We must not suppose, howevei', that

the views of those extreme glaciahsts who suppose continental ice-caps reaching half way to the equator are borne out by facts. In truth, the ice accumulating round thenbsp;pole must have been surrounded by water, and there mustnbsp;have been tree-clad islands in the midst of the icy seas,nbsp;even in the time of greatest refrigeration. This is provednbsp;by the fact that, in the Leda clay of eastern Canada,nbsp;which belongs to the time of greatest submergence, andnbsp;whose fossil shells show sea-water almost at the freezing-point, there are leaves of poplars and other plants whichnbsp;must have been drifted from neighbouring shores. Similar remains occur in clays of like origin in the basin ofnbsp;the great lakes and in the West. These have been callednbsp;�� interglacial,� but there is no evidence to prove that theynbsp;are not truly glacial. Thus, while we need not supposenbsp;that plants existed within the Arctic circle in the Glacialnbsp;age, we have evidence that those of the cold temperatenbsp;and sub-arctic zones continued to exist pretty far north.nbsp;At the same time the warm temperate flora would benbsp;driven to the south, excejat where sustained in insularnbsp;spots warmed by the equatorial currents. It would returnnbsp;northward on the re-elevation of the land and the renewal of warmth.

If, however, our modern flora is thus one that has returned from the south, this would account for its poverty in species as compared with those of the early Tertiary.nbsp;Groups of plants descending from the north have beennbsp;rich and varied. Eeturning from the south they are likenbsp;the shattered remains of a beaten army. This, at least,nbsp;has been the case with such retreating floras as those ofnbsp;the Lower Carboniferous, the Permian, and the Jurassic,nbsp;and possibly that of the Lower Eocene of Europe.

The question of the supply of light to an arctic flora is much less difficult than some have imagined. Thenbsp;long summer day is in this respect a good substitute fornbsp;a longer season of growth, while a copious covering of

winter snow not only protects evergreen plants from those sudden alternations of temperature which are more destructive than intense frost, and prevents the frost fromnbsp;penetrating to their roots, but, by the ammonia which itnbsp;absorbs, preserves their greenness. According to Dr.nbsp;Brown, the Danish ladies of Disco long ago solved thisnbsp;problem.¹ He informs us that they cultivate in theirnbsp;houses most of our garden flowers�as roses, fuchsias, andnbsp;geraniums�showing that it is merely warmth and notnbsp;light that is required to enable a subtropical flora tonbsp;thrive in Greenland. Even in Canada, which has a floranbsp;richer in some respects than that of temperate Europe,nbsp;growth is effectually arrested by cold for nearly sixnbsp;months, and though there is ample sunlight there is nonbsp;vegetation. It is, indeed, not impossible that in thenbsp;plans of the Creator the continuous summer sun of thenbsp;arctic I�egions may have been made the means for the introduction, or at least for the rapid growth and multiplication, of new and more varied types of plants.

Much, of course, remains to be known of the history of the old floras, whose fortunes I have endeavoured tonbsp;sketch, and which seem to have been driven like shuttlecocks from north to south, and from south to north,nbsp;especially on the American continent, whose meridionalnbsp;extension seems to have given a field specially suited fornbsp;such operations.

This great stretch of the western continent, from north to south, is also connected with the interesting factnbsp;that, when new floras are entering from the arctic regions, they appear earlier in America than in Europe,nbsp;and that in times when old floras are retreating from thenbsp;south old genera and species linger longer in America.nbsp;Thus, in the Devonian and Cretaceous new forms of thosenbsp;periods appear in America long before they are recognized

in Europe, and in the modern epoch forms that would he regarded in Europe as Miocene still exist. Much confusion in reasoning as to the geological ages of the fossil florasnbsp;has arisen from want of attention to this circumstance.

What we have learned respecting this wonderful history has served strangely to change some of our preconceived ideas. We must now be prepared to admit that an Eden can be planted even in Spitzbergen, that therenbsp;are possibilities in this old earth of ours which its presentnbsp;condition does not reveal to us ; that the present state ofnbsp;the world is by no means the best possible in relation tonbsp;climate and vegetation ; that there have been and mightnbsp;be again conditions which could convert the ice-clad arctic regions into blooming paradises, and which at thenbsp;same time would moderate the fervent heat of the tropics.nbsp;We are accustomed to say that nothing is impossible withnbsp;God ; but how little have we known of the gigantic possibilities which lie hidden under some of the most common of his natural laws !

These facts have naturally been made the occasion of speculations as to the spontaneous development of plantsnbsp;by processes of varietal derivation. It would, from thisnbsp;point of view, be a nice question to calculate how manynbsp;revolutions of climate would suffice to evolve the first land-plant ; what are the chances that such plant would be sonbsp;dealt with by physical changes as to be preserved andnbsp;nursed into a meagre flora like that of the Upper Siluriannbsp;or the Jurassic ; how many transportations to Greenlandnbsp;would suffice to promote such meagre flora into the richnbsp;and abundant forests of the Upper Cretaceous, and tonbsp;people the earth with the exuberant vegetation of thenbsp;early Tertiary. Such problems we may never be able tonbsp;solve. Probably they admit of no solution, unless we invoke the action of an Almighty mind, operating throughnbsp;long ages, and correlating with boundless power and wisdom all the energies inherent in inorganic and organic

nature. Even then we shall perhaps be able to comprehend only the means by which, after specific types have been created, they may, by the culture of their Maker,nbsp;be � sported � into new varieties or subspecies, and thusnbsp;fitted to exist under different conditions or to occupynbsp;higher plaees in the economy of nature.

Before venturing on such extreme speculations as some now current on questions of this kind, we wouldnbsp;require to know the successive extinct floras as perfectlynbsp;as those of the modern world, and to he able to ascertainnbsp;to what extent each species can change either spontaneously or under the influence of struggle for existence ornbsp;expansion under favourable conditions, and under arcticnbsp;semi-annual days and nights, or the shorter days of thenbsp;tropics. Such knowledge, if ever acquired, it may takenbsp;ages of investigation to accumulate.

As to the origin and mode of introduction of successive floras, I am, for the reasons above stated, not disposed to dogmatise, or to adopt as final any existing theory ofnbsp;the development of the vegetable kingdom. Still, somenbsp;laws regulating the progress of vegetable life may benbsp;recognised, and I propose to state these in connectionnbsp;with the Palaeozoic floras, to which my own studies havenbsp;chiefly related.

Fossil plants are almost proverbially uncertain with reference to their accurate determination, and have beennbsp;regarded as of comparatively little utility in the decisionnbsp;of general questions of palaeontology. This results principally from the fragmentary condition in which theynbsp;have been studied, and from the fact that fragments ofnbsp;animal structures are more definite and instructive thannbsp;corresponding portions of plants.

It is to be observed, however, that our knowledge of fossil plants becomes accurate in proportion to the extentnbsp;to which we can carry the study of specimens in the bedsnbsp;in which they are preserved, so as to examine more per-

feet examples than those usually to be found in museums. When structures are taken into the account, as well asnbsp;external forms, we can also depend more confidently onnbsp;our results. Further, the abundance of specimens to benbsp;obtained in particular beds often goes far to make up fornbsp;their individual imperfection. The writer of these pagesnbsp;has been enabled to avail himself very fully of these advantages ; and on this account, if on no other, feels entitlednbsp;to speak with some authority on theoretical questions.

It is an additional encouragement to pursue the subject, that, when we can obtain definite information as to the successive floras of any region, we thereby learn muchnbsp;as to climate and vicissitudes in regard to the extent ofnbsp;land and water; and that, with reference to such points,nbsp;the evidence of fossil jflants, when properly studied, is,nbsp;from the close relation of plants to those stations andnbsp;climates, even more valuable than that of animal fossils.

It is necessary, however, that in pursuing such inquiries we should have some definite views as to the nature and permanence of specific forms, whether withnbsp;reference to a single geological period or to successivenbsp;periods ; and I may be excused for stating here some general principles, which I think important for our guidance.

1. nbsp;nbsp;nbsp;Botanists proceed on the assumption, vindicated bynbsp;experience, that, within the period of human observation,nbsp;species have not materially varied or passed into eachnbsp;other. We may make, for practical purposes, the samenbsp;assumption with regard to any given geological period,nbsp;and may hold that for each such period there are specificnbsp;types which, for the time at least, are invariable.

2. nbsp;nbsp;nbsp;When we inquire what constitutes a good speciesnbsp;for any given period, we have reason to believe that manynbsp;names in our lists represent merely varietal forms or erroneous determinations. This is the case even in thenbsp;modern flora; and in fossil floras, through the poverty ofnbsp;specimens, their fragmentary condition, and various states

of preservation, it is still more likely to occur. Every revision of any group of fossils detects numerous synonyms, and of these many are incapable of detectionnbsp;without the comparison of large suites of specimens.

3. nbsp;nbsp;nbsp;We may select from the flora of any geological period certain forms, which I shall call specific types, whichnbsp;may for such period be regarded as unchanging. Havingnbsp;settled such types, we may compare them with similarnbsp;forms in other periods, and such comparisons will not henbsp;vitiated by the uncertainty which arises from the comparison of so-called species which may, in many cases, benbsp;mere varietal forms, as distinguished from specific types.nbsp;Our types may be founded on mere fragments, providednbsp;that these are of such a nature as to prove that they belong to distinct forms which cannot pass into each other,nbsp;at least within the limits of one geological period.

4. nbsp;nbsp;nbsp;When we compare the specific types of one periodnbsp;with those of another immediately precedent or subsequent, we shall find that some continue unchangednbsp;through long intervals of geological time, that others arenbsp;represented by allied forms regarded either as varietal ornbsp;specific, and as derived or otherwise, according to thenbsp;view which we may entertain as to the permanence ofnbsp;species. On the other hand, we also find new types notnbsp;rationally deducible on any theory of derivation fromnbsp;those known in other periods. Eurther, in comparingnbsp;the types of a poor period with those of one rich in species, we may account for the appearance of new types innbsp;the latter by the deficiency of information as to the former ; where many new types appear in the poorer periodnbsp;this conclusion seems less probable. For example, newnbsp;types appearing in poor formations, like the Lower Eriannbsp;and Lower Carboniferous, have greater significance than ifnbsp;they appeared in the Middle Erian or in the Coal Measures.

5. nbsp;nbsp;nbsp;When specific types disappear without any knownnbsp;successors, under circumstances in which it seems un-

likely that we should have failed to discover their con-tinuauce, we may fairly assume that they have become extinct, at least locally; and where the field of observation is very extensive, as in the great coal-fields of Europenbsp;and America, we may esteem such extinction as practically general, at least for the northern hemisphere.nbsp;When many specific types become extinct together, or innbsp;close succession, we may suppose that such extinctionnbsp;resulted from physical changes; but where single typesnbsp;disappear, under circumstances in which others of similarnbsp;habit continue, we may not unreasonably conjecture that,nbsp;as Pictet has argued in the case of animals, such typesnbsp;may have been in their own nature limited in duration,nbsp;and may have died out without any external cause.

6. nbsp;nbsp;nbsp;With regard to the introduction of specific typesnbsp;we have not as yet a sufficient amount of information.nbsp;Even if we freely admit that ordinary specific forms, asnbsp;well as mere varieties, may result from derivation, this bynbsp;no means excludes the idea of primitive specific typesnbsp;originating in some other way. Just as the chemist, afternbsp;analysing all compounds and ascertaining all allotropicnbsp;forms, arrives at length at certain elements not mutuallynbsp;transmutable or derivable, so the botanist and zoologistnbsp;must expect sooner or later to arrive at elementarynbsp;specific types, which, if to be accounted for at all, mustnbsp;be explained on some principle distinct from that ofnbsp;derivation. The position of many modern biologists, innbsp;presence of this question, may be logically the same withnbsp;that of the ancient alchemists with reference to thenbsp;chemical elements, though the fallacy in the case of fossils may be of more difficult detection. Our business atnbsp;present, in the prosecution of palseobotany, is to discover,nbsp;if possible, what are elementary or original types, and, having found these, to enquire as to the law of their creation.

7. nbsp;nbsp;nbsp;In prosecuting such questions geographical relations must be carefully considered. When the floras of

two suceessiTe periods have existed in the same region, and under circumstances that render it probable thatnbsp;plants have continued to grow on the same or adjoiningnbsp;areas throughout these periods, the comparison becomesnbsp;direct, and this is the case with the Erian and Carboniferous floras in northeastern America. But, when thenbsp;areas of the two formations are widely separated in spacenbsp;as well as in time, any resemblances of facies that we maynbsp;observe may have no connection whatever with an unbroken continuity of specific types.

I desire, however, under this head, to affirm my conviction that, with reference to the Erian and Carboniferous floras of North America and of Europe, the doctrine of �homotaxis,� as distinct from actual contemporaneity,nbsp;has no place. The succession of formations in the Palaso-zoic period evidences a similar series of physical phenomena on the grandest scale throughout the northern hemisphere. The succession of marine animals implies thenbsp;continuity of the sea-bottoms on which they lived. Thenbsp;headquarters of the Erian flora in America and Europenbsp;must have been in connected or adjoining areas in thenbsp;North Atlantic. The similarity of the Carboniferous floranbsp;on the two sides of the Atlantic, and the great number ofnbsp;identical species, proves a still closer connection in thatnbsp;period. These coincidences are too extensive and too frequently repeated to be the result of any accident of similarnbsp;sequence at different times, and this more especially asnbsp;they extend to the more minute differences in the features of each period, as, for instance, the floras of thenbsp;Lower and Upper Devonian, and of the Lower, Middle,nbsp;and Upper Carboniferous.

8. Another geographical question is that which relates to centres of dispersion. In times of slow subsidence ofnbsp;extensive areas, the plants inhabiting such areas must benbsp;narrowed in their range and often separated from onenbsp;another in detached spots, while, at the same time, impor-

taut climatal changes must also occur. On the re-emergence of the land such of these species as remained would again extend themselves over their former areas of distribution, in so far as the new climatal and other conditionsnbsp;would permit. We would naturally suppose that the firstnbsp;of the above processes would tend to the elimination ofnbsp;varieties, the second, to their increase ; but, on the othernbsp;hand, the breaking up of a continental flora into that ofnbsp;distinct islets, and the crowding together of many forms,nbsp;might be a process fertile in the production of some varieties if fatal to others.

Further, it is possible that these changes of subsidence may have some connection with the introduction, as wellnbsp;as with the extinction, even of specific types. It is certain, at least, in the case of land-plants, that such typesnbsp;come in most plentifully immediately after elevation,nbsp;though they are most abundantly preserved in periods ofnbsp;slow subsidence. I do not mean, however, that this connection is one of cause and effect; there are, indeed, indications that it is not so. One of these is, that in somenbsp;cases the enlargement of the area of the land seems to benbsp;as injurious to terrestrial species as its diminution.

9. Another point on which I have already insisted, and which has been found to apply to the Tertiary as well asnbsp;to the Palseozoie floras, is the appearance of new typesnbsp;within the arctic and boreal areas, and their migrationnbsp;southward. Periods in which the existence of northernnbsp;land coincided with a general warm temperature of thenbsp;northern hemisphere seem to have been those most favourable to the introduction of new forms of land-plants.nbsp;Hence, there has been throughout geological time a general movement of new floras from the Palsearctic andnbsp;Hearctic regions to the southward.

Applying the above considerations to the Brian and Carboniferous floras of North America, we obtain somenbsp;data which may guide us in arriving at general conclu-

sions. The Erian flora is comparatively poor, and its types are in the main similar to those of the Carboniferous. Of these types a few only reappear in the middlenbsp;coal-formation under identical forms; a great number appear under allied forms ; some altogether disappear. Thenbsp;Erian flora of New Brunswick and Maine occurs side bynbsp;side with the Carboniferous of the same region; so doesnbsp;the Erian of New York and Pennsylvania with the Carboniferous of those States. Thus we have data for thenbsp;comparison of successive floras in the same region. Innbsp;the Canadian region we have, indeed, in direct sequence,nbsp;the floras of the Upper Silurian, the Lower, Middle, andnbsp;Upper Brian, and the Lower, Middle, and Upper Carboniferous, all more or less distinct from each other, andnbsp;affording an admirable series for comparison in a regionnbsp;whose geographical features are very broadly marked.nbsp;All these floras are composed in great part of similarnbsp;types, and probably do not indicate very dissimilar generalnbsp;physical conditions, but they are separated from eachnbsp;other by the great subsidences of the Corniferous limestone and the Lower Carboniferous limestone, and by thenbsp;local but intense subterranean action which has alterednbsp;and disturbed the Erian beds toward the close of thatnbsp;period. Still, these changes were not universal. Thenbsp;Corniferous limestone is absent in Gasp�, and probably innbsp;New Brunswick, where, consequently, the Erian floranbsp;could continue undisturbed during that long period.nbsp;The Carboniferous limestone is absent from the slopes ofnbsp;the Appalachians in Pennsylvania, where a retreat maynbsp;have been afforded to the Upper Erian and Lower Carboniferous floras. The disturbances at the close of thenbsp;Erian were limited to those eastern regions where thenbsp;great limestone-producing subsidences were unfelt, and,nbsp;on the other hand, are absent in Ohio, where the subsidences and marine conditions were almost at a maximum.

GENERAL LAWS OF ORIGIN AND MIGRATION. 265

Bearing in mind these peculiarities of the area in question, we may now group in a tabular form the distinct specific types recognised in the Erian system, indicating, at the same time, those which are represented bynbsp;identical species in the Carboniferous, those representednbsp;by similar species of the same general type, and those notnbsp;represented at all. Eor example, Galamites cannmformisnbsp;extends as a species into the Carboniferous ; Asterophyl-lites latifolia does not so extend, hut is represented bynbsp;closely allied species of the same type; Nematophytonnbsp;disappears altogether before we reach the Carboniferous.

Table of Erian and Carboniferous Specific Types.

�c lt;0	.'�gt; (C				BQ
	.2 B	Erian rimes. Represented in		H 0lt; 2 amp;	s s

^ lt;3	M�S			08 C� V	w-g
		2T.	Cordaites Robbii.....		*
		28.	C. angustifolia......
		29.	Arch^opteris Jacksoni
		30.	AneimitCvS obtusa.....
		31.	Platyphyllum Brownii.
	*	82.	Cyclopteris varia.....		��
	*	83.	C. obtusa............
	*	34.	Neuropteris polymor-
			pha..............		�X-
	*	35.	N. serrulata.........		*
*		86.	N. retorquata........		*
*		37.	N. resecta...........
		38.	Megalopteris Dawsoni.
		39.	Sphenopteris Hoening-
	*		hausi.............	*
		40.	S. Harttii...........		*
		41.	Hymenophyllitea curti-
	*
		42.	H. obtusilobus.......		*
		43.	Aletliopteris discrepans		*
		44.	Pecopteris serrulata...
		45.	P. preciosa..........
*		46.	Trichomanites........
	*	47.	Callipteris..........		*
		48.	Cardiocarpum.......
		49.	C. Crampii..........
	*	60.	Antholithes.........		*
		61.	Trigonocarpum......		*

Of the above forms, fifty-one in all, found in the Brian of eastern America, all, except the last four, are certainlynbsp;distinct specific types. Of these only four reappear in thenbsp;Carboniferous under identical species, but no less thannbsp;twenty-six reappear under representative or allied forms,nbsp;some at least of which a derivationist might claim asnbsp;modified descendants. On the other hand, nearly onenbsp;half of the Devonian types are unknown in the Carboniferous, while there remain a very large number of Carboniferous types not accounted for by anything known innbsp;the Devonian. Further, a very poor flora, including onlynbsp;two or three types, is the predecessor of the Brian flora innbsp;the Upper Silurian, and the flora again becomes poor innbsp;the Upper Devonian and Lower Carboniferous. Bverynbsp;new species discovered must more or less modify the abovenbsp;statements, and the whole Brian flora of America, as wellnbsp;as the Carboniferous, requires a thorough comparison withnbsp;that of Europe before general conclusions can be safelynbsp;drawn. In the mean time I may indicate the direction innbsp;which the facts seem to point by the following generalnbsp;statements :

1. Some of the forms reckoned as specific in the Devonian and Carboniferous may be really derivative races. There are indications that such races may have originatednbsp;in one or more of the following ways : (1) By a naturalnbsp;tendency in synthetic types to become specialised in thenbsp;direction of one or other of their constituent elements.nbsp;In this way such plants as Arthrostigma and Psilophytonnbsp;may have assumed new varietal forms. (2) By embryonic retardation or acceleration,¹ whereby certain speciesnbsp;may have had their maturity advanced or postponed, thusnbsp;giving them various grades of perfection in reproductionnbsp;and complexity of structure. The fact that so manynbsp;Brian and Carboniferous plants seem to be on the con-

fines of the groups of Acrogens and Gymnosperms may be supposed fayourable to such exchanges. (3) The contraction and breaking up of floras, as occurred in thenbsp;Middle Brian and Lower Carboniferous, may have beennbsp;eminently favourable to the production of such varietalnbsp;forms as would result from what has been called thenbsp;� struggle for existence.� (4) The elevation of a greatnbsp;expanse of new land at the close of the Middle Brian andnbsp;the beginning of the coal period would, by permittingnbsp;the extension of species over wide areas and fertile soils,nbsp;and by removing the pressure previously existing, benbsp;eminently favourable to the production of new, and especially of improved, varieties.

2. nbsp;nbsp;nbsp;Whatever importance we may attach to the abovenbsp;supposed causes of change, we still require to accountnbsp;for the origin of our specific types. This may forevernbsp;elude our observation, but we may at least hope to ascertain the external conditions favourable to their production. In order to attain even to this it will be necessarynbsp;to inquire critically, with reference to every acknowledged species, what its claims to distinctness are, so thatnbsp;we may be enabled to distinguish specific types fromnbsp;mere varieties. Having attained to some certainty innbsp;this, we may be prepared to inquire whether the conditions favourable to the appearance of new varieties werenbsp;also those favourable to the creation of new types, or thenbsp;reverse�whether these conditions were those of compression or expansion, or to what extent the appearance ofnbsp;new types may be independent of any external conditions, other than those absolutely necessary for theirnbsp;existence. I am not without hope that the further studynbsp;of fossil plants may enable us thus to approach to a comprehension of the laws of the creation, as distinguishednbsp;from those of the continued existence of species.

3. nbsp;nbsp;nbsp;In the present state of our knowledge we have nonbsp;good ground either to limit the number of specific types

beyond what a fair study of our material may warrant, or to infer that such primitive types must necessarilynbsp;have been of low grade, or that progress in varietal formsnbsp;has always been upward. The occurrence of such annbsp;advanced and specialised type as that of Dadoxylonnbsp;in the Middle Devonian should guard us against thesenbsp;errors. The creative process may have been applicablenbsp;to the highest as well as to the lowest forms, and subsequent deviations must have included degradation as wellnbsp;as elevation. I can conceive nothing more unreasonablenbsp;than the statement sometimes made that it is illogical ornbsp;even absurd to suppose that highly organised beingsnbsp;could have been jproduced except by derivation from previously existing organisms. This is begging the wholenbsp;question at issue, depriving science of a noble departmentnbsp;of inquiry on which it has as yet barely entered, and anticipating by unwarranted assertions conclusions whichnbsp;may perhaps suddenly dawn upon us through the inspiration of some great intellect, or may for generations tonbsp;come baffle the united exertions of all the earnest promoters of natural science. Our present attitude shouldnbsp;not be that of dogmatists, but that of patient workersnbsp;content to labour for a harvest of grand generalisationsnbsp;which may not come till we have passed away, but which,nbsp;if we are earnest and true to Ifature and its Creator, maynbsp;reward even some of us.

Within the human period great changes of distribution of plants have occurred, chiefly through the agency of man himself, and we have had ample evidence thatnbsp;plants are able to establish themselves and prosper innbsp;climates and conditions to which unaided they could notnbsp;have transported themselves, as, for instance, in the casenbsp;of European weeds naturalised in Australia and New Zealand. There is, however, no reason to believe that anynbsp;specific change has occurred to any plant within the Pleistocene or modern period.

In a recent address, delivered to the biological section of the British Association, Mr. Carruthers has discussednbsp;this question, and has shown that the earliest vegetablenbsp;specimens described by Dr. Schweinfurth from the Egyptian tombs present no appearance of change. This factnbsp;appears also in the leaves and other organs of plants preserved in the nodules in the Pleistocene clays of the Ottawa, and in specimens of similar age found in variousnbsp;places in Britain and the continent of Europe.¹

The difficulties attending the ordinary theories of evolution as applied to plants have been well set forth bynbsp;the same able botanist in his �Presidential Address tonbsp;the Geological Association in 1877,� a paper which deserves careful study. One of his illustrations is thatnbsp;ancient willow, Salix polaris, referred to in a previousnbsp;chapter, which now lives in the arctic regions, and isnbsp;found fossil in the Pleistocene beds at Cromer and atnbsp;Bovey Tracey.

He notes the fact that the genus Salix is a very variable one, including 19 subgeneric groups and 160 species, with no less than 222 varieties and 70 hybrids. Salixnbsp;polaris belongs to a subgeneric group containing 29nbsp;species, which are arranged in four sections, that tonbsp;which S. polaris belongs containing six species. Now itnbsp;is easy to construct a theoretical phylogeny of the derivation of the willows from a supposed ancestral source,nbsp;but when we take our little S. polaris we find that thisnbsp;one twig of our ancestral tree takes us hack withoutnbsp;change to the Glacial jieriod. The six species would takenbsp;us still farther, and the sections, subgenera, and genusnbsp;at the same rate would require an incalculable amount ofnbsp;past time. He concludes the inquiry in the followingnbsp;terms :

�Proceedings British Association,� 1886, �Pleistocene Plants of Canada,� Canadian Naturalist, 1866.

�But when we have reached the branch representing the generic form we have made but little progress in thenbsp;phylogenesis of Salix. With Populus this genus formsnbsp;a small order, Salicinese. The two genera are closelynbsp;allied, yet separated by well-marked characters; it isnbsp;not, however, difficult to conceive of both having sprungnbsp;from a generalised form. But there is no record of suchnbsp;a form. The two genera appear together among thenbsp;earliest known dicotyledons, the willows being represented by six and the poplars by nine species. The ordinal form, if it ever existed, must necessarily be muchnbsp;older than the period of the Upper Cretaceous rocks,nbsp;that is, than the period to which the earliest knownnbsp;dicotyledons belong.

�The Salicinese are related to five other natural orders, in all of which the apetalous flowers are arrangednbsp;in catkins. These different though allied orders mustnbsp;be led up by small modifications to a generalised amentiferous type, and thereafter the various groups of apetalous plants by innumerable eliminations of differentiatingnbsp;characters until the primitive form of the apetalous plantnbsp;is reached. Beyond this the uncurbed imagination willnbsp;have more active work in bridging over the gap betweennbsp;Angiosperms and Gymnosperms, in finding the intermediate forms that led up to the vascular cryptogams, andnbsp;on through the cellular plants to the primordial germ.nbsp;Every step in this phylogenetic tree must he imagined.nbsp;The earliest dicotyledon takes us not a step farther backnbsp;in the phylogenetic history of Salix than that suppliednbsp;by existing vegetation. All beyond the testimony of ournbsp;living willows is pure imagination, unsupported by anbsp;single fact. So that here, also, the evidence is againstnbsp;evolution, and there is none in favour of it.�

It is easy to see that similar difficulties beset every attempt to trace the development of plants on the principle of slow and gradual evolution, and we are driven

back on the theory of periods of rapid origin, as we have already seen suggested by Saporta in the case of the Cretaceous dicotyledons. Such abrupt and plentiful introduction of species over large areas at the same time, bynbsp;whatever cause effected�and we are at present quite ignorant of any secondary causes�becomes in effect somethingnbsp;not unlike the old and familiar idea of creation. Sciencenbsp;must indeed always be baffled by questions of ultimatenbsp;origin, and, however far it may be able to trace the chainnbsp;of secondary causation and development, must at lengthnbsp;find itself in the presence of the great Creative Mind,nbsp;who is � before all things and in whom all things consist.�

APPENDIX.

I.�COMPARATIVE VIEW OF THE SECCESSIVE PALEOZOIC FLORAS OF NORTHEASTERN AMERICA AND GREAT BRITAIN.

In eastern Canada there is a very complete series of fossil plants, extending from the Silurian to the Permian, and intermediate in itsnbsp;species between the floras of interior America and of Europe. I maynbsp;use this succession, mainly worked out by myself,¹ to summarise thenbsp;various Palfeozoic floras and sub-floras, in order to give a condensednbsp;view of this portion of the history of the vegetable kingdom, and tonbsp;direct attention to the important fact, too often overlooked, thatnbsp;there is a definite succession of fossil plants as well as of animals,nbsp;and that this is important as a means of determining geologicalnbsp;horizons. A British list for comparison has been kindly preparednbsp;for me by Mr. R. Kidston, F. G. S. For lists referring to the western and southern portions of America, I may refer to the reports ofnbsp;Lesquereux and Fontaine and White.f

In this connection I am reminded, by an excellent little paper of M. Zeiller, i on Carboniferous plants from the region of the Zambesi,nbsp;in Africa, that the flora which in the Carboniferous period extendednbsp;over the temperate portions of the northern hemisphere and far intonbsp;the arctic, also passed across the equator and prevailed in the southern hemisphere. Of eleven species brought from the Zambesi by M.nbsp;Lapierre and examined by M. Zeiller, all were identical with Euro-

�Acadian Geology,� �Reports on Fossil Plants of Canada,� Geological Survey of Canada.

pean species of the upper coal-formation, and the same fact has been observed in the coal flora of the Cape Colony.¹ These facts bearnbsp;testimony to the remarkable uniformity of climate and vegetation innbsp;the coal period, and I perfectly agree with Zeiller that they show,nbsp;when taken in connection with other parallelisms in fossils, an actualnbsp;contemporaneousness of the coal flora over the whole world.

This occurs in the upper member of the Carboniferous system of Nova Scotia and Prince Edward Island, originally named by thenbsp;writer the Newer Coal-formation, and more recently the Permo-Carboniferous, and the upper beds of which may not improbably benbsp;contemporaneous with the Lower Permian or Lower Dyas of Europe.nbsp;In this formation there is a predominance of red sandstones andnbsp;shales, and it contains no productive beds of coal. Its fossil plantsnbsp;are for the most part of species found in the Middle or Productivenbsp;Coal-formation, but are less numerous, and there are a few new formsnbsp;akin to those of the European Permian. The most characteristicnbsp;species of the upper portion of the formation, which has the mostnbsp;decidedly Permian aspect, are the following;

Of these species, those marked with an asterisk have not yet been found in the middle or lower members of the Carboniferous system.nbsp;They will be found described, and several of them figured, in mynbsp;� Keport on the Geology of Prince Edward Island.� f The others are

common and widely diffused Carboniferous species, some of which have extended to the Permian period in Europe as well. Prom thenbsp;upper beds, characterised by these and a few other species, there is anbsp;gradual passage downward into the productive coal-measures, and anbsp;gradually increasing number of true coal-formation species.

It is worthy of remark here that the association in the Permo-Carboniferous of numerous trunks of Dadoxylon with the branches of WalcJiia and with fruits of the character of Trigonocarpa, seemsnbsp;to show that these were parts of one and the same plant.

This formation represents the Upper Barren Measures of West Virginia, which are well described by Fontaine and White,¹ and thenbsp;reasons which these authors adduce for considering the latter equivalent to the European Permian will apply to the more northern andnbsp;eastern deposits as well, though these have afforded fewer species ofnbsp;plants, and are apparently less fully developed.

The Middle or Productive Coal-formation, containing all the beds of coal which are mined in Nova Scotia and Cape Breton, is the headquarters of the Carboniferous flora. Prom this formation I havenbsp;catalogued f one hundred and thirty-five species of plants; but, asnbsp;several of these are founded on imperfect specimens, the number ofnbsp;actual species may be estimated at one hundred and twenty. Ofnbsp;these more than one half are species common to Europe and America.nbsp;No less than nineteen species are Sigillarim, and about the samenbsp;number are Lepidodendra. About fifty are ferns and thirteen arenbsp;Calamites, Asterophyllites, and Sphenophylla. The great abundancenbsp;and number of species of Sigillarim, Lepidodendra, and ferns arenbsp;characteristic of this sub-flora; and among the ferns certain speciesnbsp;of Neuropteris, Pecopteris, Alefhopteria, and Sphenopteris greatlynbsp;preponderate.

These beds are the equivalents of the Middle Coal-measures, or Productive Coal-measures of Pennsylvania, Ohio, amp;c., and of thenbsp;coal-formation proper of various European countries. Very manynbsp;of the species are common to Nova Scotia and Pennsylvania; but innbsp;proceeding westward the number of identical species seems to diminish.

� Report on the Permian Flora of Western Virginia and South Pennsylvania,� 1880.

f �Acadian Geology,� and �Report on Flora of Lower Carboniferous,� ISIS.

In this formation the abundance of plants and the number of species are greatly diminished.¹ Trunks of coniferous trees of thenbsp;species Dadoxylon Aeadianum, having wide wood-cells with threenbsp;or more series of discs and complex meduUary rays, become characteristic. Catamites undulatwm is abundant and seems to replace C.nbsp;SucJcovii, though C. cannceformis and C. cistii continue. Sigillarianbsp;become very rare, and the species of Lepidodendron are few, andnbsp;mostly those with large leaf-bases. Lepidophloios still continues, andnbsp;Cordaites abounds in some beds. The ferns are greatly reduced,nbsp;though a few characteristic coal-formation species occur, and thenbsp;genus Gardiopteris appears. Beds of coal are rare in this formation;nbsp;but where they occur there is in connection with them a remarkablenbsp;anticipation of the rich coal-formation flora, which would thus seemnbsp;to have existed locally in the Millstone Grit period, but to havenbsp;found itself limited by generally unfavorable conditions. In America, as in Europe, it is in the north that this earlier development ofnbsp;the coal-flora occurs, while in the south there is a lingering of oldnbsp;forms in the newer beds. In Newfoundland and Cape Breton, fornbsp;instance, as well as in Scotland, productive coal-beds and a greaternbsp;variety of species of plants occur in this formation.

The following would appear to be the equivalents of this formation, in flora and geological position:

2. nbsp;nbsp;nbsp;The Lower Coal-formation Conglomerate and Chester groupsnbsp;of Illinois (Worthen).

3. nbsp;nbsp;nbsp;The Lower Carboniferous Sandstone of Kentucky, Alabama,nbsp;and Virginia.

4. nbsp;nbsp;nbsp;The Millstone Grit and Yoredale rocks of northern England,nbsp;and the Culmiferous of Devonshire.

6. nbsp;nbsp;nbsp;Flagstones and Lower Shales of the south of Ireland, and Millstone Grit of the north of Ireland.

This affords few fossil plants in eastern America, and in so far as known they are similar to those of the next group. In Scotland itnbsp;is richer in plants, but, according to Mr. Kidston, these are largely

� Report on Fossil Plants of the Lower Carboniferous and Millstone Grit of Canada,� 1873.

similar to those of the underlying beds, though with some species which extend upward into the Millstone Grit. In Scotland the alganbsp;named Spirophyton and Archmocalamites radiatus�which in America are Krian�appear in this formation.

This group of plants is best seen in the shales of the Horton series, under the Lower Carboniferous marine limestones. It isnbsp;small and peculiar. The most characteristic species are the following:

Dadoxylon {Palaioxylon) antiquius, Dn.�A species with large medullary rays of three or more series of cells.

Lepidodendron corrugatum, Ln.�A species closely allied to L. Veltheimianum of Europe, and which is its American representative.nbsp;This is perhaps the most characteristic plant of the formation. Itnbsp;is very abundant, and presents very protean appearances, in its oldnbsp;stems, branches, twigs, and Knorria forms. It had well-characterised stigmaria roots, and constitutes the oldest erect forest known innbsp;Nova Scotia.

The four species last mentioned are comparatively rare, and the specimens are usually too imperfect to render their identificationnbsp;certain, but Lepidodendra are especially characteristic trees of thisnbsp;horizon.

Cyclopteris (Aneimites) Acadica, Dn.�A very characteristic fern, allied in the form of its fronds to C. tenuifolia of Qoeppert, to C.nbsp;nana of Eiohwald, and to Adiantites antiquus of Stur. Its fructification, however, is nearer to that of Aneimia than to that of Adi-antum.

Ptilophyton plumula, Dn.�This is the latest appearance of this Erian genus, which also occurs in the Lower Carboniferous of Europe and of the United States.

On the whole, this small flora is markedly distinct from that of the Millstone Grit and true coal-formation, from which it is separated by the great length of time required for the deposition of thenbsp;marine limestones and their associated beds, in which no land-plants

have been found; nor is this gap filled up by the conglomerates and coarse arenaceous beds which, as I have explained in � Acadian Geology,� in some localities take the place of the limestones, as they donbsp;also in the Appalachian region farther south.

The paliBobotanicai and strategraphical equivalents of this series abroad would seem to be the following:

6. nbsp;nbsp;nbsp;The Caloiferous sandstones of McLaren, or Tweedian group ofnbsp;Tate in Scotland.

7. nbsp;nbsp;nbsp;The Lower Carboniferous slate and Coomhala grits of Jukesnbsp;in Ireland.

9. nbsp;nbsp;nbsp;The Graywaoke or Lower Coal-measures of the Vosges, as described by Sohimper.

10. nbsp;nbsp;nbsp;The Older Coal-formation of the Ural, as described by Eich-wald.

11. nbsp;nbsp;nbsp;The so-called � Ursa Stage � of Heer includes this, but he hasnbsp;united it with Devonian beds, so that the name cannot be used except for the local development of these beds at Bear Island, Spitz-borgen. The Carboniferous plants of arctic America, Melville Island, amp;o., as well as those of Spitzbergen, appear all to be Lowernbsp;Carboniferous.¹

All of the above groups of rocks are characterised by the prevalence of Lepidodendra of the type of L. eorrugatum, L. Veltheimia-mm, and L. Glincanum ; pines of the sub-genus Pitus of Witham, Palmoxylon of Brongniart, and peculiar ferns of the genera Gy-clopteria, Cardiopteris, Tripliyllopteris, and Sphenopteris. In all thenbsp;regions above referred to they form the natural base of the greatnbsp;Carboniferous system.

In Virginia, according to Fontaine and White, types, such as Archceopteria, which in the north are Upper Brian, occur in thisnbsp;group. Unless there have been some errors in fixing the iower limitnbsp;of the Vespertine, this would indicate a longer continuance of oldnbsp;forms in the south.

� Notes on Geological Map of the Northern Portion of the Dominion of Canada,� by Dr. G. M. Dawson, 1887.

This corresponds to the Catskill and Chemung of the New York series, and to the Upper Devonian of Europe.

The flora of this formation, which consists mostly of sandstones, is not rich. Its most distinctive species on both sides of the Atlanticnbsp;seem to be the ferns of the genus Archmopteris, along with speciesnbsp;referred to the genus Gyclopteris, but which, in so far as their barrennbsp;fronds are concerned, for the most part resemble Archmopteris.

The characteristic American species are Archmopteris Jachsoni, A. Rogersi, and A. Gaspiensis. Gyclopteris ohtusa and G. {Platy-phyllum) Brownii are also very characteristic species. In Europe,nbsp;Archmopteris Hibernica is a prevalent species.

Leptophleum rhombicum and fragments of Psilophyton are also found in the Upper Erian. There is evidence of the existence ofnbsp;vast numbers of Rhizocarps in this period, in the deposits of spore-cases {Sporangites Huronensis) in the shales of Kettle Point, Lakenbsp;Huron; and in deposits of similar character in Ohio and elsewherenbsp;in the West.

The Upper Erian flora is thus very distinct from that of the Lower Carboniferous, and the unconformahle relation of the beds innbsp;the Northeast may perhaps indicate a considerable lapse of time.nbsp;Still, even in localities where there appears to be a transition fromnbsp;the Carboniferous into the Devonian, as in the Western States andnbsp;in Ireland, the characteristic flora of each formation may be distinguished, though, as already stated, there is apparently some mixturenbsp;in the South.

Both in Canada and the United States that part of the great Erian system which may be regarded as its middle division, thenbsp;Hamilton and Marcellus shales of New York, the Cordaites shales ofnbsp;St. John, New Brunswick, and the middle shales and sandstones ofnbsp;the Gasp� series, presents conditions more favourable to the abundantnbsp;growth of land-plants than either the upper or lower member. Innbsp;the St. John beds, in particular, there is a rich fern flora, comparablenbsp;with that of the coal-formation, and numerous stipes of ferns andnbsp;trunks of tree-ferns have been found in the Hamilton and Cornifer-ous series in the West, as well as trunks of Dadoxylon. It is, however, distinguished by a prevalence of small and delicate species, andnbsp;by such forms as Hymenophyllites and the smaller Sphenopterids,nbsp;and also by some peculiar ferns, as Archmopteris and Megalopteris.

In addition to ferns, it has small Lepidodendra, of which L. Gaspi-a/rmm is the chief. CalamitecB occur, ArchcBocalamites radiatus being the dominant species. This plant, which in Europe appears to reachnbsp;up into the Lower Carboniferous, is so far strictly Brian in northeast America. Sigillarice scarcely appear, but Cordaites is abundant, and the earliest known species of Dadoxylon appear, while thenbsp;Psilophyton, so characteristic of the Lower Brian, still continues,nbsp;and the remarkable aquatic plants of the genus Ptilophyton arenbsp;locally abundant.

This belongs to the Lower Devonian sandstones and shales, and is best seen in that formation at Gasp� and the Bay des Chaleurs. Itnbsp;is equivalent to the Oriskany sandstone, so far as its animal fossilsnbsp;and mineral character are concerned. It is characterised by the absence of true ferns, Calamites and Sigillarice, and by the presencenbsp;of such forms as Psilophyton, Arthrostigma, Leptophleum, and Ne-matophyton. Lepidodendron Gaspianum and Leptophleum alreadynbsp;occur, though not nearly so abundant as Psilophyton.

The Lower Brian plants have an antique and generalised aspect which would lead us to infer that they are near the beginning of thenbsp;land-flora, or perhaps in part belong to the close of an earlier floranbsp;still in great part unknown; and few indications of land-plants havenbsp;been found earlier.

At Campbellton and Soaumenac Bay, on the Bay des Chaleurs, fossil fishes of genera characteristic of the Lower and Upper Devonian horizons respectively, occur in association with fossil plantsnbsp;of these horizons, and have been described by Mr. Whiteaves.*

It is interesting to note that, as Fontaine and White have observed, certain forms which are Brian in the northeast are found in the Lower members of the Carboniferous in West Virginia, indicating the southward march of species in these periods.

In the upper beds of the Silurian, those of the Helderberg series, we still find Psilophyton and Nematophyton; but below these wenbsp;know no land-plants in Canada. In the United States, Lesquereuxnbsp;and Claypole have described remains which may indicate the existence of lycopodiaceous and annul arian types as far back as the be-

APPENDIX.

ginning of the Upper Silurian, or even as low as the Hudson River group, and Hicks has found Nematophyton and Psilophyton in bedsnbsp;about as old in Wales, along with the uncertain stems named Ber-�vynia. In the Lower Silurian the Protannularia of the Skiddawnbsp;series in England may represent a land-plant, but this is uncertain,nbsp;and no similar species has been found in Canada.

The Cambrian rocks are so far barren of land-plants; the so-called Eophyton being evidently nothing but markings, probably produced by crustaceans and other aquatic animals. In the stillnbsp;older Laurentian the abundant beds of graphite probably indicatenbsp;the existence of plants, but whether aquatic or terrestrial it is impossible to decide at present.

It would thus appear that our certain knowledge of land-vegetation begins with the Upper Silurian or the Silurio-C'ambrian, and that its earliest forms were Acrogens allied to Lycopods, and prototypal trees, forerunners of the Acrogens or the gymnosperms. Innbsp;the Lower Devonian little advance is made. In the Middle Devoniannbsp;this meagre flora had been replaced by one rivalling that of the Carboniferous, and including pines, tree-ferns, and arboreal forms ofnbsp;Lycopods and of equisetaoeous plants, as well as numerous herbaceous plants. At the close of the Erian the flora again becamenbsp;meagre, and continued so in the Lower Carboniferous. It again became rich and varied in the Middle Carboniferous, to decay in thenbsp;succeeding Permian.

IL�HEER�S LATEST RESULTS IN THE GREENLAND FLORA.

A VERY valuable report of Prof. Steenstrup, published in Copenhagen in 1883, the year in which Heer died, contains the results of his last work on the Greenland plants, and is so important that anbsp;summary of its contents will be interesting to all students of fossilnbsp;botany or of the vicissitudes of climate which the earth has undergone.¹

1. The Komi series, of black shales resting on the Laurentian gneiss. These beds are found at various other localities, but the

name above given is that by which they are generally kni vn. Their flora is limited to ferns, cycads, conifers, and a few endogens, withnbsp;only Populus primosva to represent the dicotyledons. These bedsnbsp;are regarded as Lower Cretaceous (Urgonian), but the animal fossilsnbsp;would seem to give them a rather higher position. They may benbsp;regarded as equivalent to the Kootanie and Queen Charlotte beds innbsp;Canada, and the Potomac series in Virginia.

2. The Atan� series. These also are black shales with dark-coloured sandstones. They are best exposed at Upernavik and Waigat. Here dicotyledonous leaves abound, amounting to ninetynbsp;species, or more than half the whole number of species found.nbsp;The fossil plants resemble those of the Dakota series of the Unitednbsp;States and the Dunvegan series of Canada, and the animal fossilsnbsp;indicate the horizon of the Port Pierre or its lower part. They maynbsp;be regarded as representing the lower part of the Upper Cretaceous.nbsp;The genera Populus, Myrica, Quercus, Ficus, Platanus, Sassafras,nbsp;Laurus, Magnolia, and Liriodendron are among those representednbsp;in these beds, and the peculiar genera Macclintockia and Crednerianbsp;are characteristic. The genus Pinus is represented by five species.nbsp;Sequoia by five, and Salisburia by two, with three of the alliednbsp;genus Baiera. There are many ferns and cycads.

8. The Paloot series. These are yellow and red shales, which seem to owe their colour to the spontaneous combustion of pyritousnbsp;lignite, in the manner observed on the South Saskatchewan and thenbsp;Mackenzie rivers. Their age is probably about that of the Fox-Hillnbsp;group or Senonian, and the Upper Cretaceous of Vancouver Island,nbsp;and they afford a large proportion of dicotyledonous leaves. Thenbsp;genera of dicotyledons are not dissimilar from those of Atan�, butnbsp;we now recognise Betula and Alnus, Comptonia, Planera, Sapo-tacites, Fraxinus, Viburnum, Cornus, Acer, Celastrus, Paliurua,nbsp;Ceanothus, Zizyphus, and Gratcegus as new genera of modern aspect.

On the whole there have been found in all these beds 335 species, belonging to 60 families, of which 36 are dicotyledonous, and represent all the leading types of arborescent dicotyledons of the temperate latitudes. The flora is a warm temperate one, with some remarkable mixtures of sub-tropical forms, among which perhaps thenbsp;most remarkable are Kaidocarpum referred to the Pandanem, andnbsp;such exogens as Ficus and Cinnamomvm.

4. The Unartok series. This is believed to be Eocene. It consists of sandstone, which appears on the shores of Disco Island, and

possibly at some other places on the coast. The beds rest directly and apparently conformably on the Upper Cretaceous, and have afforded only eleven species of plants. Magnolia is represented bynbsp;two species, Laurus by two, Platanus by two, and one of these saidnbsp;to be identical with a species found by Lesquereux in the Laramie,¹nbsp;Viburnum, Juglans, Quercus, each by one species; the ubiquitousnbsp;Sequoias by S. Langsdorffii. This is pretty clearly a Lower Laramienbsp;flora.

5. The Atamlcerdluh series, consisting of shaly beds, with limestone intercalated between great sheets of basalt, much like the Eocene of Antrim and the Hebrides. These beds have yielded 187nbsp;species, principally in bands and concretions of siderite, and oftennbsp;in a good state of preservation. They are referred to the Lowernbsp;Miocene, but, as explained in the text, the flora is more nearly akinnbsp;to that of the Eocene of Europe and the Laramie of America. Thenbsp;animal fossils are chiefly fresh-water shells. Onoclea sensibilis,nbsp;several conifers, as Taxites Olrihi, Taxodmm disticlmm, Glyptostro-hus Europmus, and Sequoia Langsdorffii, and 42 of the dicotyledonsnbsp;are recognised as found also in American localities. Of these, anbsp;large proportion of the more common species occur in the Laramienbsp;of the Mackenzie River and elsewhere in northwest Canada, and innbsp;the western United States. It is quite likely also that several species regarded as distinct may prove to be identical.

It would seem that throughout the whole thickness of these Tertiary beds the flora is similar, so that it is probable it belongs altogether to the Eocene rather than to the Miocene.

No indication has been observed of any period of cold intervening between the Lower Cretaceous and the top of the Tertiary deposits,nbsp;so that, in all the vast period which these formations represent, thenbsp;climate of Greenland would seem to have been temperate. Therenbsp;is, however, as is the case farther south, evidence of a gradual diminution of temperature. In the Lower Cretaceous the probable meannbsp;annual temperature in latitude 71� north is stated as 21� to 22�nbsp;centigrade, while in the early Tertiary it is estimated at 12� centigrade. Such temperatures, ranging from 71� to 53� of Fahrenheit,nbsp;represent a marvellously warm climate for so high a latitude. Innbsp;point of fact, however, the evidence of warm climates in the arcticnbsp;regions, in the Palajozoic as well as in the Mesozoic and early Tertiary, should perhaps lead us to conclude that, relatively to the wholenbsp;of geological time, the present arctic climate is unusually severe, and

that a temperate climate in the arctic regions has throughout geological time been the rule rather than the exception.

The state of preserYation of fossil plants has been referred to incidentally in several places in the text; but the following morenbsp;definite statements may be of service to the reader.

I. nbsp;nbsp;nbsp;Organic remains imbedded in aqueous deposits may occur innbsp;an unchanged condition, or only more or less altered by decay. Thisnbsp;is often the case with such enduring substances as bark and wood,nbsp;and even with leaves, which appear as thin carbonaceous films whennbsp;the layers containing them are split open. In the more recent deposits such remains occur little modified, or perhaps only slightlynbsp;changed by partial decay of their more perishable parts. In thenbsp;older formations, however, they are usually found in a more ornbsp;less altered condition, in which their original substance has beennbsp;wholly or in part changed into coaly, or bituminous, or anthraciticnbsp;or graphitic matter, so that leaves are sometimes represented by stainsnbsp;of graphite, as if drawn on stone with a lead-pencil. Yet even innbsp;this case some portion of the original substance remains, and withoutnbsp;any introduction of foreign material.

II. nbsp;nbsp;nbsp;On the other hand, such remains are often mineralised by thenbsp;filling of their pores or the replacement of their tissues with mineralnbsp;matter, so that they become hard and stony, and sometimes retainnbsp;little or nothing of their original substance. The more importantnbsp;of these changes, in so far as they affleot fossil plants, may be arranged under the following heads:

(a) nbsp;nbsp;nbsp;Infiltration of mineral matter which has penetrated the poresnbsp;of the fossil in a state of solution. Thus the pores of fossil woodnbsp;are often filled with calcite, quartz, oxide of iron, or sulphide of iron,nbsp;while the woody walls of the cells and vessels remain in a carbonisednbsp;state, or converted into coaly matter. When wood is preserved innbsp;this way it has a hard and stony aspect; but we can sometimes dissolve away the mineral matter, and restore the vegetable tissue to anbsp;condition resembling that before mineralisation. This is especiallynbsp;the case when calcite is the mineralising substance. We sometimesnbsp;find, on microscopic examination, that even cavities so small as thosenbsp;of vegetable cells and vessels have been filled with successive coatsnbsp;of different kinds of mineral matter.

(b) nbsp;nbsp;nbsp;Organic matters may be entirely replaced by mineral substances. In this case the cavities and pores have been first filled.

and then�the �walls or solid parts being removed by decay or solution�mineral matter, either similar to that filling the cavities, or differing in colour or composition, has been introduced. Silioiflednbsp;wood often occurs in this condition. In the case of silicified wood,nbsp;it sometimes happens that the cavities of the fibers have been fillednbsp;with silica, and the wood has been afterward removed by decay,nbsp;leaving the casts of the tubular fibers as a loose filamentous substance. Some of the Tertiary coniferous woods of California are innbsp;this state, and look like asbestus, though they show the minutenbsp;markings of the tissue under the microscope. In the case of silicifiednbsp;or agatized woods, it would seem that the production of carbon dioxide from the decaying wood has caused the deposition of silica innbsp;its place, from alkaline solutions of that substance, and thus thenbsp;carbon has been replaced, atom by atom, by silicon, until the wholenbsp;mass has been silicified, yet retaining perfectly its structure.

(c) The cavities left by fossils which have decayed may be filled with clay, sand, or other foreign matter, and this, becoming subsequently hardened into stone, may constitute a cast of the fossils.nbsp;Trunks of trees, roots, amp;o., are often preserved in this way, appearingnbsp;as stony casts, often with the outer bark of the plant forming a carbonaceous coating on their surfaces. In connection with this statenbsp;may be mentioned that in which, the wood having decayed, an entirenbsp;trunk has been fiattened so as to appear merely as a compressed filmnbsp;of bark, yet retaining its markings; and that in which the whole ofnbsp;the vegetable matter having been removed, a mere impression ofnbsp;the form remains.

Fossils preserved in either of the modes, (a) or (5), usually show more or less of their minute structures under the microscope. Thesenbsp;may be observed:�(1) By breaking off small splinters or flakes andnbsp;examining them, either as opaque or as transparent objects. (2) Bynbsp;treating the material with acids, so as to dissolve out the mineralnbsp;matters, or portions of them. This method is especially applicablenbsp;to fossil woods mineralised with calcite or pyrite. (3) By grindingnbsp;thin sections. These are first polished on one face on a coarse stonenbsp;or emery hone, and then on a fine hone, then attached by the polishednbsp;face to glass slips with a transparent cement or Canada balsam, andnbsp;ground on the opposite face until they become so thin as to be translucent. In most cities there are lapidaries who prepare slices of thisnbsp;kind; but the amateur can readily acquire the art by a little practice, and the necessary appliances can be obtained through dealersnbsp;in minerals or in microscopic materials. Very convenient cuttingnbsp;and polishing machines, some of them quite small and portable, are

now made for the use of amateurs. In the case of exogenous woods, three sections are necessary to exhibit the whole of the structures.nbsp;One of these should be transverse and two longitudinal, the latter innbsp;radial and tangential planes.

In the text frequent reference has been made to special memoirs and reports on the fossil plants of particular regions or formations.nbsp;There are, however, some general books, useful to students, whichnbsp;may be mentioned here. Perhaps the most important is Schimper�snbsp;� Trait� de Paleontologie V�g�tale.� Very useful information isnbsp;also contained in Renault�s � Cours de Botanique Possile,� and innbsp;Balfour�s � Introduction to Palaeontological Botany,� and Nicholson�s � Palaeontology.� Unger�s � Genera et Species,� Brongniart�snbsp;� Histoire des V�g�taux Fossiles,� and Bindley and Hutton�s � Fossilnbsp;Flora,� are older though very valuable works. Williamson�s � Memoirs,� in the � Philosophical Transactions,� have greatly advancednbsp;our knowledge of the structures of Palaeozoic plants. Lastly, thenbsp;� Palaeophytology � of Schenk, now in course of publication in German and French, in connection with Zittel�s � Palaeontology,� is annbsp;important addition to manuals of the subject.

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SPECIMEN OF TYPE.

Would blow me to an ague, when I thought What harm a wind too great might do at sea.

I should not see the sandy hour-glass run But I should think of shallows and of flats,.

Vailing her high-top lower than her ribs To kiss her burial. Should I go to churchnbsp;And see the holy edifice of stone,

And not bethink me straight of dangerous rocks, Which touching but my gentle vessel�s side.

And now worth nothing ? Shall I have the thought To think on this, and shall I lack the thoughtnbsp;That such a thing bechanc�d would make me sad ?nbsp;But tell not me : I know Antonionbsp;Is sad to think upon his merchandise.

Ant. Believe me, no : I thank my fortune for it, My ventures are not in one bottom trusted,

Nor to one place ; nor is my whole estate Upon the fortune of this present year :

Because you are not merry; and �twere as easy For you to laugh, and leap, and say you are merry,nbsp;Because you are not sad. Now, by two-headednbsp;Janus,

Some that will evermore peep through their eyes And laugh like parrots at a bag-piper ;

ANIMALS.	SYSTEMS OF FOEMATIONS.		PLANTS.
Age of Man and Mammalia.	II �3	Modem, Pleistocene, Pliocene, Miocene, Eocene.	Angiospenns and Palms dominant.
Age of Eeptiles.	'5 Cretaceous, o Jurassic, S Triassic. S 1		Cjcads and Pines dominant.
Age of AmphibiaBS and Fishes. Age of Inverte-brates.	.2 �o N o J J Pk	' Permian, Carboniferous, Brian, Silurian, Ordovician, Cambrian, Huronian (Upper).	Acrogens and Gym-nosperms dominant.
Age of Protozoa.	.2 �o . N O	Huronian (Lower), Upper Laurentian,nbsp;Middle Laurentian,nbsp;Lower Laurentian.	Protogens and Algse.

Subdivisions.	New York and Western Canada.	Gasp� and Bay des Cbaleurs.	Southern New Brunswick.	Coast of Maine.
Upper Devonian or Erian.	Chemung Group.	Upper Sandstones.nbsp;Long Cove, amp;c.nbsp;Scauminacnbsp;Beds.	Mispec Group. Shale, Sandstone, andnbsp;Conglomerate.	Perry Sandstones.
Middle Devonian ornbsp;Erian.	Hamilton Group.	Middle Sandstones.nbsp;Bois Brul�,nbsp;Cape Oiseau,nbsp;amp;c.	LittleR.Group (includingnbsp;Cordaitenbsp;Shales andnbsp;Dadoxylonnbsp;Sandstone).
Lower Devonian or Erian,	Corniferous and Oriskany groups.	Lower Sandstones.nbsp;Gasp� Basin,nbsp;Little Gasp�,nbsp;amp;c. Campbellton Beds.	Lower Conglomerates, amp;c.

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GEOLOGICAL HISTORY OF PI, A NTS

PEEFAOE

OO�^TENTS.

CHAPTER I.

CHAPTER II.

CHAPTER III.

CHAPTER IV.

CHAPTER V.

CHAPTER VI.

CONTENTS.

CHAPTER VII.

CHAPTER VIII.

. 237

APPENDIX.

LIST OF ILLTJSTRATIOFTS.

geological history of plants.

ronian.

CHAPTER III.

with Archmopteris is that which I have named Platyphyl-lum, and which grew on a creeping stem or parasitically on stems of other plants, and had marginal fructification.1

various heights on the stem, and which form a series of stays like the cordage of a ship. This method of support

still continues in the modern tree-ferns of the tropics and the southern hemisphere. In one kind of tree-fern

THE ERIAN OR DEVONIAN FORESTS.

THE CARBONIFEROUS FLORA.

f9T�r�r�i

THE CARBONIFEROUS FLORA.

THE GEOLOGICAL HISTORY OF PLANTS.

NOTE TO CHAPTER V.

I APPEND to this chapter a table showing the plant-bearing series of the Cretaceous and Laramie of North America, from a paper innbsp;� Trans. B. S. C.,� 1885, which see for further details:

Ill

GENERAL LAWS OF ORIGIN AND MIGRATION. 265

Table of Erian and Carboniferous Specific Types.

APPENDIX.

APPENDIX.

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with Archmopteris is that which I have named Platyphyl-lum, and which grew on a creeping stem or parasitically on stems of other plants, and had marginal fructification.¹