CHAPTER VI.. The Reign of Angiosperms in the Later Cretaceous

THE REIGN OF ANGIOSPERMS IN THE LATER CRETACEOUS AND KAINOZOIC.

It is a remarkable fact in geological chronology that the culmination of the vegetable kingdom antedates that of the animal. The placental mammals, the highest group of the animal kingdom, are not known till the beginning of the Eocene Tertiary. The dicotyledonous Angiosperms, which correspond to them in the vegetable kingdom, occur far earlier--in the beginning of the Upper Cretaceous or close of the Lower Cretaceous. The reign of cycads and pines holds throughout the Lower Cretaceous, but at the close of that age there is a sudden incoming of the higher plants, and a proportionate decrease, more especially of the cycads.

I have already referred to the angiospermous wood supposed to be Devonian, but I fear to rest any conclusion on this isolated fact. Beyond this, the earliest indications of plants of this class have been found in the Lower Cretaceous. Many years ago Heer described and figured the leaves of a poplar (Populus primæva) from the supposed Lower Cretaceous of Komé, in Greenland (Fig. 68). Two species, a Sterculia and a Laurus or Salix, occur among fossils described by me in the upper part of the Kootanie series of the Rocky Mountains, and Fontaine has recently found in the Potomac group of Virginia--believed to be of Neocomian age--several angiospermous species (Sassafras, Menispermites, Sapindus, Aralia, Populus, &c.) mixed with a rich flora of cycads and pines. These are the early forerunners of the modern angiospermous flora; but so far as known they do not occur below the Cretaceous, and in its lower portions only very rarely. When, however, we ascend into the Upper Cretaceous, whether of Europe or America, there is a remarkable incoming of the higher plants, under generic forms similar to those now existing. This is, in truth, the advent of the modern flora of the temperate regions of the earth. A very interesting tabular view of its early distribution is given by Ward, in the "American Journal of Science" for 1884, of which the following is a synopsis, with slight emendations. I may add that the new discoveries made since 1884 would probably tend to increase the proportionate number of dicotyledons in the newer groups.

Dicotyledonous Trees in the Cretaceous.

Upper Senonian 179 species. (Fox Hill group of America.)

Lower Senonian 81 species. Upper white chalk of Europe; Fort Pierre group of America; coal-measures of Nanaimo?

Turonian 20 species. Lower white chalk; New Jersey marls; Belly R. group.

Cenomanian. 357 species. (Chalk-marl, greensand, and Gault, Niobrara and Dakota groups of America); Dunvegan group of Canada; Amboy clays of New Jersey.

Neocomian 20 species. (Lower greensand and Speeton clay, Wealden and Hastings sands, Kootanie and Queen Charlotte groups of Canada.)

Including an estimate of Fontaine's undescribed species.

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

"Monde des Plantes," p. 197.

The leaves described by Heer, from the Middle Cretaceous of Greenland, are those of a poplar (P. primæva). Those which I have described from a corresponding horizon in the Rocky Mountains are a Sterculites (S. vetustula), probably allied to the mallows, and an elongated leaf, Laurophyllum (L. crassinerve) (Fig. 69), which may, however, have belonged to a willow rather than a laurel. These are certainly older than the Dakota group 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, as already stated, has found an abundant flora of cycads, conifers, and ferns, with a few angiospermous leaves, which have not yet been described.

In the Canadian Rocky Mountains, a few hundreds of feet above the beds holding the beforementioned species, are the shales of the Mill Creek series, rich in many species of dicotyledonous leaves, and corresponding in age with the Dakota group, whose fossils have been so well described, first by Heer and Capellini, and afterward by Lesquereux. We may take this Dakota group and the quader-sand stone of Germany as types of the plant-bearing Cenomanian, and may 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, Glyptostrobus, Gingko, and even Pinus itself. We also have a few cycads, but not so dominant as in the previous ages. The fan-palms are well represented, both in America and in the corresponding series in Europe, especially by the genus Sabal, which is the characteristic American type of fan-palm, and there is one genus which Saporta regards as intermediate between the fan-palms and the pinnately 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.

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 richness of the time in plants of this type. It may be necessary to explain here that the generic names used are mostly 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, on the other hand, that plants of different genera may be very much alike in their foliage. There is, however, undoubtedly a likeness in plan or type of structure in leaves of closely allied plants, and, therefore, if judiciously studied, they can be determined with at least approximate certainty. More especially we can attain to much certainty when the fruits as well as the leaves are found, and when we can obtain specimens of the wood, showing its structure. Such corroboration is not wanting, though unfortunately the leaves of trees are generally found drifted away from the other organs once connected with them. In my own experience, however, I have often found determinations of the leaves of trees confirmed by the discovery of their fruits or of the structure of their stems. Thus, in the rich cretaceous plant-beds of the Dunvegan series we have beech-nuts associated in the same beds with leaves referred to Fagus. In the Laramie beds I determined many years ago nuts of the Trapa or water-chestnut, and subsequently Lesquereux found, in beds in the United States, leaves which he referred to the same genus. Later, I found in collections made on the Red Deer River of Canada my fruits and Lesquereux's leaves on the same slab. The presence of trees of the genera Carya and Juglans in the same formation was inferred from their leaves, and specimens have since been obtained of silicified wood, with the microscopic structure of the modern butternut. Still we are willing to admit that determinations from leaves alone are liable to doubt.

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

In the matter of names of fossil leaves, I sympathise very strongly with Dr. Nathorst, of Stockholm, in his objection to the use of modern generic names for mere leaves, and would be quite content to adopt some non-committal termination, as that of "phyllum" or "ites" suggested by him. I feel, however, that almost as much is taken for granted if a plant is called Corylophyllum or Corylites, as if called Corylus. In either case a judgment is expressed as to its affinities, which if wrong under the one term is wrong under the other; and after so much has been done by so many eminent botanists, it seems inexpedient to change the whole nomenclature for so small and questionable an advantage. I wish it, however, to be distinctly understood that plants catalogued on the evidence of leaves alone are for the most part referred to certain genera on grounds necessarily imperfect, and their names are therefore subject to correction, as new facts may be obtained.

The more noteworthy modern genera included in the Dakota flora, as catalogued by Lesquereux, are the following: Liquidambar, the sweet-gum, is represented both in America and Europe, the leaves resembling those of the modern species, but with entire edges, which seems to be a common peculiarity of Cretaceous foliage. Populus (poplar), as already stated, appears very early in Greenland, and continues with increasing number of species throughout the Cretaceous and Tertiary. Salix (willow) appears only a little later and continues. Of the family Cupuliferæ we have Fagus (beech), Quercus (oak), and Castanea (chestnut), which appear together in the Dakota group and its equivalents. Fruits of some of the species are known, and also wood showing structure. Betula (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 Plat anus (Fig. 71), 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, where there are several species with immense leaves. The large leaves, known as Credneria, found in the Cenomanian of Europe, and those called Protophyllum (Fig. 72) in America, appear to be nearer to the plane-trees than to any others, though representing an extinct type. The laurels are represented in this age, and the American genus Sassafras, which has now only one species, has not one merely but several species in the Cretaceous. Diospyros, the persimmon-tree, was also a Cretaceous genus.

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

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 the Cretaceous (Fig. 73). The walnut family were well represented by species of Juglans (butternut) and Carya, or hickory. In all, no less than forty-eight genera are present belonging to at least twenty-five families, running through the whole range of the dicotyledonous exogens. This is a remarkable result, indicating a sudden profusion of forms of these plants of a very striking character. It is further to be observed that some of the genera have many species in the Cretaceous and dwindle toward the modern. In others the reverse is the case--they have expanded in modern times. In a number there seems to have been little change.

Dr. Newberry has given, in the "Bulletin of the Torrey Botanical Club" an interesting résumé of the history of the beautiful Liriodendron, or tulip-tree, which may be taken as an example of a genus which has gone down in importance in the course of its geological history.

"The genus Liriodendron, as all botanists know, is represented in the present flora by a single species, 'the tulip-tree' which is confined to eastern America, but grows over all the area lying between the Lakes and the Gulf, the Mississippi and the 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 its associates in size, while the beauty of its glossy, lyre-shaped leaves and tulip-like flowers is only surpassed by the flowers and foliage of its first cousin, Magnolia grandiflora. That a plant so splendid should stand quite alone in the vegetation of the present day excited the wonder of the earlier botanists, but the sassafras, the sweet-gum, and the great Sequoias of the far West afford similar examples of isolation, and the latter are still more striking illustrations of solitary grandeur." (Figs. 74 and 75.)

"Three species of Liriodendron are indicated by leaves found in the Amboy clays--Middle Cretaceous--of New Jersey, and others have been obtained from the Dakota group in the West, and from the Upper Cretaceous strata of Greenland. Though differing considerably among themselves in size and form, all these have the deep sinus of the upper extremity so characteristic of the genus, and the nervation is also essentially the same. Hence, we must conclude that the genus Liriodendron, now represented by a single species, was in the Cretaceous age much more largely developed, having many species, and those scattered throughout many lands. In the Tertiary age the genus continued to exist, but the species seem to have been reduced to one, which is hardly to be distinguished from that now living. In many parts of Europe leaves of the tulip-tree have been found, and it extended as far south as Italy. Its presence there was first made known by Unger, in his 'Synopsis,' page 232, and in his 'Genera et Species,' page 443, where he describes it under the name of Liriodendron procaccinii. The genus has also been noticed in Europe by Massalongo, Heer, and Ettingshausen, and three species have been distinguished. All these are, however, so much like the living species that they should probably be united with it. We here have a striking illustration of the wide distribution of a species which has retained its characters both of fruit and leaf quite unchanged through long migrations and an enormous lapse of time.

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

Leaves of Liriodendron have been recognised in the Cretaceous of Greenland, though it is now a tree of the warm temperate region, and Lesquereux describes several species from the Dakota group. But the genus has not yet been recognised in the Laramie or in the Upper Cretaceous of British Columbia. In the paper above quoted, Newberry describes three new species from the Amboy clays, one of which he considers identical with a Greenland form referred by Heer to L. Meekii of the Dakota group. Thus, if all Lesquereux's species are to be accepted, the genus begins in the Middle Cretaceous with at least nine American species.

In New Jersey the Amboy clays are referred to the same age with the Dakota beds of the West. In these Dr. Newberry has found a rich flora, including many angiosperms. The following is condensed from a preliminary notice in the "Bulletin of the Torrey Botanical Club":

March, 1886.

"The flora of the Amboy clays is closely related to that of the Dakota group--most of the genera and some of the species being identical--so that we may conclude they were nearly contemporaneous, though the absence in New Jersey of the Fort Benton and Niobrara groups of the upper Missouri and the apparent synchronism of the New Jersey marls and the Pierre group indicate that the 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), which not only indicates a chronological parallelism, but shows a remarkable and unexpected similarity in the vegetation of these widely separated countries in the middle and last half of the Cretaceous age. The botanical character of the flora of the Amboy clays will be seen from the following brief synopsis:

"Algæ.--A small and delicate form, allied to Chondrites.

"Ferns.--Twelve species, generally similar and in part identical with those described by Heer from the Cretaceous beds of Greenland, and referred to the genera Dicksonia, Gleichenia, and Aspidium.

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

"Conifers.--Fourteen species, belonging to the genera Moriconia, Brachyphyllum, Cunninghamites, Pinus, Sequoia, and others referred by Heer to Juniperus, Libocedrus, Frenelopsis, Thuya, and Dammara. Of these, the most abundant and most interesting are Moriconia cyclotoxon--the most beautiful of conifers--and Cunninghamites elegans, both of which occur in the Cretaceous clays of Aachen, Prussia, and Patoot, Greenland. The 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 or four of Salix, three of Celastrophyllum (of which one is identical with a Greenland species), one Celastrus (also found in Greenland), four or five Aralias, two Sassafras, one Cinnamomum, one Hedera; with leaves that are apparently identical with those described by Heer as belonging to Andromeda, Cissites, Cornus, Dewalquea, Diospyros, Eucalyptus, Ficus, Ilex, Juglans, Laurus, Menispermites, Myrica, Myrsine, Prunus, Rhamnus, and others not yet determined.

"Some of the Aralias had palmately-lobed leaves, nearly a foot in diameter, and two of the tulip-trees (Liriodendron) had leaves quite as large as those of the living species. One of these had deeply lobed leaves, like those of the white oak. Of the other, the leaves resembled those of the recent tulip-tree, but were larger. Both had the peculiar emargination and the nervation of Liriodendron.

"Among the most interesting plants of the collection are fine species of Bauhinia and Hymenæa. Of these, the first is represented by a large number of leaves, some of which are six or seven inches in diameter. They are deeply bilobed, and have the peculiar and characteristic form and nervation of the leaves of this genus. Bauhinia is a leguminous genus allied to Cercis, and now inhabits tropical and warm temperate climates in both hemispheres. Only one species occurs in the United States, Bauhinia lunarioides, Gray, found by Dr. Bigelow on the Rio Grande.

"Hymenæa is another of the leguminosæ, 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 are much larger, and the leaflets are united in a common petiole, which is winged; this is a modification not found in the living species, and one which brings it nearer to Bauhinia.

"But the most surprising discovery yet made is that of a number of quite large helianthoid flowers, which I have called Palæanthus. These are three to four inches in diameter, and exhibit a scaly involucre, enclosing what much resembles a fleshy receptacle with achenia. From the border of this radiate a number of ray florets, one to two inches in length, which are persistent and must have been scarious, like those of Helichrysum. Though these flowers so much resemble those of the compositæ, we are not yet warranted in asserting that such is certainly their character. In the Jurassic rocks of Europe and India some flowers not very unlike these have been found, which have been named Williamsonia, and referred to cycads by Carruthers. 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 genus to the Cycadeæ, and agrees with Nathorst in considering all the species of Williamsonia as parasitic flowers, allied to Brugmansia or Rafflesia. The Marquis of Saporta regards them as monocotyledons, similar to Pandanus. More specimens of the flowers now exhibited will perhaps prove--what we can now only regard as probable--that the Compositæ, like the Leguminosæ, Magnoliaceæ, Celastraceæ, 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, it has been supposed that they belonged only to the recent 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 composite type presents a startling illustration of the early appearance of a very elevated and complex form. Great interest also attaches to these Amboy beds, as serving, with those of Aix and Greenland, to show that the margins of the Atlantic were occupied with a flora similar to that occurring at the same time in the interior plateau of North America and on the Pacific slope.

The beds at Aix-la-Chapelle are, however, probably somewhat newer than the Dakota or Amboy beds, and correspond more nearly in age with those of the Cretaceous coal-field of Vancouver Island, where there is a very rich Upper Cretaceous flora, which I have noticed in detail in the "Transactions of the Royal Society of Canada." In these Upper 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 is corroborated by the Upper Cretaceous flora of Atané and Patoot in Greenland, as described by Heer.

Vol. ii., 1884.

The dicotyledonous plants above referred to are trees and shrubs. Of the herbaceous exogens of the period we know less. Obviously their leaves are less likely to find their way into aqueous deposits than the leaves of trees. They are, besides, more perishable, and in densely wooded countries there are comparatively few herbaceous plants. 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 for the leaves of herbaceous plants.

The climate of North America and Europe, represented by the Cenomanian vegetation, is not tropical but warm temperate; but the flora was more uniform than at present, indicating a very equable climate and the possibility of temperate genera existing within the Arctic circle, and it would seem to have become warmer toward the close of 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. This depends on great movements of elevation and depression, to which we must refer in the sequel. In a few regions, however, as in the vicinity of the Peace River in Canada, there are plant-bearing beds which serve to bridge over the interval between the Early Cenomanian and the later Cretaceous.

See paper by the author in the "Transactions of the Royal Society of Canada," 1882.

To this interval also would seem to belong the Belly River series of western Canada, which contains important beds of Coal, but is Closely associated with the marine Fort Pierre series. A very curious herbaceous plant of this group, which I have named Brasenia antiqua, occurs in the beds associated with one of the coals. It is a close ally of the modern B. peltata, an aquatic plant which occurs in British Columbia and in eastern America, and is also said to be found in Japan, Australia, and India, a width of distribution appropriate to so old a type (Fig. 76).

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

In the first instance an important error was committed by palæobotanists, in referring to the Miocene many deposits really belonging to the Eocene. This arose from the early study of the rich plant-bearing Miocene beds of Switzerland, and from the similarity of the flora all the way from the Middle Cretaceous to the later Tertiary. The differences are now being worked out, and we owe to Mr. Starkie Gardner the credit of pointing these out in England, and to the Geological Survey of Canada that of collecting the material for 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 with beds of lignite, some of them eighteen feet in thickness. This was formerly known as the lignitic or lignite Tertiary, but more recently as the Laramie series. These beds were deposited in fresh or brackish water, in an internal sea or group of lakes and swamps, when the continent was lower than at present. They have been studied both in the United States and Canada; and, though their flora was originally referred by mistake to the Miocene, it is now known to be Eocene or Palæocene, or even in part a transition group between the latter and the Cretaceous. The following remarks, taken chiefly from recent papers by the author, will serve to illustrate this:

See more especially the elaborate and valuable reports by Lesquereux and Newberry, and a recent memoir by Ward on "Types of the Laramie Flora," "Bulletins of the United States Geological Survey," 1887.

"Transactions of the Royal Society of Canada," 1886-'87.

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 large areas west of the 100th meridian, and separated from each other by a tract of older Cretaceous rocks, over which the 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 distance along the United States boundary, between the 102d and 109th meridians, and reaches northward to about thirty miles south of the "elbow" of the South Saskatchewan River, which is on the parallel of 51° north. In this area the lowest beds of the Laramie are seen to rest on those of the Fox Hill group of the Upper Cretaceous, and at one point on the west they are overlaid by beds of Miocene Tertiary age, observed by Mr. McConnell, of the Geological Survey, in the Cypress Hills, and referred by Cope, on the evidence of mammalian remains, to the White River division of the United States geologists, which is regarded by them as Lower Miocene. The age of the Laramie beds is thus stratigraphically determined to be between the Fox Hill Cretaceous and the Lower Miocene. They are also undoubtedly continuous with the Fort Union group of the United States geologists on the other side of the international boundary, and they contain similar fossil plants. They are divisible into two groups--a lower, mostly argillaceous, and to which the name of "Bad Lands beds" may be given, from the "bad lands" of Wood Mountain, where they are well exposed, and an upper, partly arenaceous member, which may be named the Souris River or Porcupine Creek division. In the lower division are found reptilian remains of Upper Cretaceous type, with some fish remains more nearly akin to those of the Eocene. Neither division has as yet afforded mammalian remains.

"Report of the Geological Survey of Canada," 1885.

Cope, in Dr. G. M. Dawson's "Report on the 49th Parallel."

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 of latitude, and stretches eastward to the 111th meridian. In this area, and more especially in its southern part, the officers of the Geological Survey of Canada have recognised three divisions, as follows: (1) The Lower Laramie or St. Mary River series, corresponding in its character and fossils to the Lower or Bad Lands division of the other area. (2) A middle division, the Willow Creek beds, consisting of clays, mostly reddish, and not recognised in the other area. (3) The Upper Laramie or Porcupine Hills division, corresponding in fossils, and to some extent in mineral character, to the Souris River 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, and a collection subsequently made by Dr. Selwyn was described in the "Report of the Geological Survey of 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, have been described in the "Transactions of the Royal Society of Canada" vols. iii. and iv.

In studying these fossil plants, I have found that there is a close correspondence between those of the Lower and Upper Laramie in the two areas above referred to respectively, and that the flora of the Lower Laramie is somewhat distinct from that of the Upper, the former being especially rich in certain aquatic plants, and the latter much more copious on the whole, and much more rich in remains of forest-trees. This is, however, possibly an effect rather of local conditions than of any considerable change in the flora, since some Upper Laramie forms recur as low as the Belly River series of the Cretaceous, which is believed on stratigraphical grounds 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 from the tendency of palæobotanists to refer the plants of the Upper Laramie to the Miocene age, although in the reports of Mr. Clarence King, the late director of the United States Geological Survey, these beds are classed, on the evidence of stratigraphy and animal fossils, as Upper Cretaceous. More recently, however, and partly perhaps in consequence of the views maintained by the writer since 1875, some change of opinion has occurred, and Dr. Newberry and Mr. Lesquereux seem now inclined to admit that what in Canada we recognise as Upper Laramie is really Eocene, and the Lower Laramie either Cretaceous or a transition group between this and the Eocene. In a recent paper Dr. Newberry gives a comparative table, in which he correlates the Lower Laramie with the Upper Cretaceous of Vancouver Island and the Faxoe and Maestricht beds of Europe, while he regards the Upper Laramie as equivalent to European Eocene. Except in so far as the equivalence of the Lower Laramie and Vancouver Island beds is concerned, this corresponds very nearly with the conclusions of the writer in a paper published last year--namely, that we must either regard the Laramie as a transition Cretaceo-Eocene group, or must institute our line of separation in the Willow Creek or Middle Laramie division, which has, however, as yet afforded no fossil plants. I doubt, however, the equivalence of the Vancouver beds and the Lower Laramie, except perhaps in so far as the upper member of the former is concerned. I have also to observe that in the latest report of Mr. Lesquereux he still seems to retain in the Miocene certain formations in the West, which from their fossil plants I should be inclined to regard as Eocene.

Newberry, "Transactions of the New Fork Academy," February, 1886.

"Transactions of the Royal Society of Canada," vol. ii.

While these sheets were going through the press I received a very valuable report of Mr. Lester F. Ward upon the Laramie of the United States. I have merely had time to glance at this report, but can see that the views of the author agree closely with those above expressed.

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. Onoclea sensibilis, the very common sensitive fern of eastern America, is extremely abundant in the Laramie beds over a great area in the West. Mr. Starkie Gardner and Dr. Newberry have also shown that it is identical with the Filicites Hebridicus of Forbes, from the early Eocene beds of the Island of Mull, in Scotland. Thus we have a species once common to Europe and America, but now restricted to the latter, and which has continued to exist over all the vast ages between the Cretaceous and the present day. In the Laramie beds I have found associated with this species another and more delicate fern, the modern Davallia (Stenloma) tenuifolia, but this, unlike its companion, no longer occurs in America, but is found in the mountains of Asia. This is a curious illustration of the fact that frail and delicate plants may be more ancient than the mountains or plains on which they live.

There are also some very interesting and curious facts in connection with the conifers of the Laramie. One of the most common of these is a Thuja or arbor vitæ (the so-called "cedar" of Canada). The Laramie species has been named T. interrupta by Newberry, but it approaches very closely in its foliage to T. occidentalis, of eastern Canada, while its fruit resembles that of the western species, T. gigantea.

Still more remarkable are the Sequoias to which we have already referred, but which in the Laramie age seem to have been spread over nearly all North America. The fossil species are of two types, representing respectively the modern S. gigantea and S. sempervirens, and their wood, as well as that of Thuja, is found in great abundance in the lignites, and also in the form of silicified trunks, and corresponds with that of the recent species. The Laramie contains also conifers of the genera Glyptostrobus, Taxodium, and Taxus; and the genus Salisburia or gingko--so characteristic of the Jurassic and Cretaceous--is still represented in America as well as in Europe in the early Eocene.

We have no palms in the Canadian or Scottish Palæocene, though I believe they are found further south. The dicotyledonous trees are richly represented. Perhaps the most conspicuous were three species of Platanus, the leaves of which sometimes fill the sandstones, and one of which, P. nobilis, Newberry, sometimes attains the gigantic size of a foot or more in diameter of its blade. The hazels are represented by a large-leaved species, C. Macquarrii, and by leaves not distinguishable from those of the modern American species, C. Americana and C. rostrata. There are also chestnuts and oaks. But the poplars and willows are specially abundant, being represented by no less than six species, and it would seem that all the modern types of poplar, as indicated by the forms and venation of the leaves, existed already in the Laramie, and most of them even in the Upper Cretaceous. Sassafras is represented by two species, and the beautiful group of Viburnum,, to which the modern tree-cranberry belongs, has several fine species, of some of which both leaves and berries have been found. The hickories and butternuts are also present, the horse-chestnut, the Catalpa and Sapindus, and some curious leaves which seem to indicate the presence of the modern genus Symphorocarpus, 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 for details to the works of Newberry, Lesquereux, and Ward, already cited. I must now add that the so-called Miocene of Atanekerdluk, Greenland, is really of the same age, as also the "Miocene" of Mull, in Scotland, of Antrim, in Ireland, and of Bovey Tracey, in the south of England, and the Gelinden, or "Heersian" beds, of Belgium, described by Saporta. In comparing the American specimens with the descriptions given by Gardner of the leaf-beds at Ardtown, in Mull, we find, as already stated, Onoclea sensibilis, common to both. The species of Sequoia, Gingko, Taxus, and Glyptostrobus are also identical or closely allied, and so are many of the dicotyledonous leaves. For example, Platanoides Hebridicus is very near to P. nobilis, and Corylus Macquarrii is common to both formations, as well as Populus Arctica and P. Richardsoni. I may add that ever since 1875-'76, 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 River and Greenland, and that the whole are Paleocene; and this conclusion has now been confirmed 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 and the Wahsatch Eocene, thus placing the Laramie conformably below the Lower Eocene of that region. Cope has also described as the Puerta group a series of beds holding vertebrate fossils, and forming a transition from the Laramie to the Wahsatch. White also testifies that a number of fresh-water mollusks are common to the Wahsatch and the Laramie. This finally settles the position of the Laramie so far as the United States geologists are concerned, and shows that the flora is to be regarded as Eocene if not Upper Cretaceous, in harmony with what has been all along maintained in Canada. An important résumé of the flora has just been issued by Ward in the 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 in these periods some allowance must be made for local differences of station, and also that there is a generic sameness in the flora of the northern hemisphere, from the Cenomanian to the modern, yet these local differences and general similarity are not of a nature to invalidate inferences as to age. No doubt, so long as palæobotanists seemed obliged, in deference to authority, and to the results of investigations limited to a few European localities, to group together, without distinction, all the floras of the later Cretaceous and earlier Tertiary, irrespective of stratigraphical considerations, the subject lost its geological importance. But, when a good series has been obtained in any one region of some extent, the 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 is sufficient to enable any competent observer to distinguish by their fossil plants the Lower, Middle, and Upper Cretaceous, and the latter from the Tertiary; and, with the aid of the work already done by Lesquereux and Newberry in the United States, to refer approximately to its true geological position any group of plants from beds of unknown age in the West.

An important consequence arising from the above statements is that the period of warm climate which enabled a temperate flora to exist in Greenland was that of the later Cretaceous and early Eocene rather than, as usually stated, the Miocene. It is also a question admitting of discussion whether the Eocene flora of latitudes so different as those of Greenland, Mackenzie River, northwest Canada, and the United States, were strictly contemporaneous, or successive within a long geological period in which climatal changes were gradually proceeding. The latter statement must apply at least to the beginning and close of the period; but the plants themselves have something to say in favour of contemporaneity. The flora of the Laramie is not a tropical but a temperate flora, showing no doubt that a much more equable climate prevailed in the more northern parts of America than at present. But this equability of climate implies the possibility of a great geographical range on the part of plants. Thus it is quite possible and indeed highly probable that in the Laramie age a somewhat uniform flora extended from the Arctic seas through the great central plateau of America far to the 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 of climate between Greenland and England, and even between Scotland and Ireland and the south of England, and we have similar differences, though not strongly-marked, between the Laramie of northern Canada and that of the United States. When all our beds of this age from the Arctic sea to the 49th parallel have been ransacked for plants, and when the palæobotanists of the United States shall have succeeded in unravelling the confusion which now exists between their Laramie and the Middle Tertiary, the geologist of the future will be able to restore with much certainty the distribution of the vast forests which in the early Eocene covered the now bare plains of interior America. Further, since the break which in western Europe separates the flora of the Cretaceous from that of the Eocene does not exist in America, it will then be possible to trace the succession from the Mesozoic flora of the Trias and of the Queen 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 conditions under which the angiospermous flora of the later Cretaceous succeeded to the pines and cycads which characterised the beginning of the Cretaceous period. In so far as Europe is concerned, this may be more difficult, since the want of continuity of land from north to south seems there to have been fatal to the continuance of some plants during changes of climate, and there were also apparently in the Kainozoic period invasions at certain times of species from the south and east, which did not occur to the same extent in America.

In recent reports on the Tertiary floras of Australia and New Zealand, 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. It would thus seem that the present geographical diversities must have largely arisen from the great changes in climate and distribution of land and water in the later Tertiary.

"Geological Magazine," August, 1887.

The length of our discussion of the early angiospermous 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 refer to the magnificent publications of Heer and Lesquereux on the Tertiary floras of Europe and America respectively.