Between 1870 and 1873 my attention was turned to the two sub-floras intermediate between those of the Devonian and the coal-formation, the floras of the Lower Carboniferous (Subcarboniferous of some American geologists) and the Millstone Grit, and in a report upon these[EJ] similar deductions were expressed. It was stated that in Newfoundland the coal-beds seem to belong to the Millstone Grit series, and as we proceed southward they belong to progressively newer portions of the Carboniferous system. The same fact is observed in the coal-beds of Scotland, as compared with those of England, and it indicates that the coal-formation flora, like that of the Devonian, spread itself from the north, and this accords with the somewhat extensive occurrence of Lower Carboniferous rocks and fossils in the Parry Islands and elsewhere in the arctic regions.
[EJ] “Fossil Plants of Lower Carboniferous and Millstone Grit Formations of Canada,” pp. 47, ten plates, Montreal, 1873.
Passing over the comparatively poor flora of the earlier Mesozoic, consisting largely of cycads, pines, and ferns, and as yet little known in the arctic, and which may have originated in the south, though represented, according to Heer, by the supposed Jurassic flora of Siberia, we find, especially at Komé and Atané in Greenland, an interesting occurrence of those earliest precursors of the truly modern forms of plants which appear in the Cretaceous, the period of the English chalk and of the New Jersey greensands. There are two plant-groups of this age in Greenland; one, that of Komé, consists almost entirely of ferns, cycads, and pines, and is of decidedly Mesozoic aspect. This is called Lower Cretaceous. The other, that of Atané, holds remains of many modern temperate genera, as Populus, Myrica, Ficus, Sassafras, and Magnolia. This is regarded as Upper Cretaceous. Resting upon these Upper Cretaceous beds, without the intervention of any other formation,[EK] are beds rich in plants of much more modern appearance, and referred by Heer to the Miocene period, a reference, as we have seen, not warranted by comparison with the Tertiary plants of Europe or of America. Still farther north this so-called Miocene assemblage of plants appears in Spitzbergen and Grinnell Land; but there, owing to the predominance of trees allied to the spruces, it has a decidedly more boreal character than in Greenland, as might be anticipated from its nearer approach to the pole.[EL]
[EK] Nordenskiöld, “Expedition to Greenland,” “Geological Magazine,” 1872.
[EL] Yet even here the bald cypress (Taxodium distichum), or a tree nearly allied to it, is found, though this species is now limited to the Southern States. Fielden and De Ranee, “Journal of the Geological Society,” 1878.
If now we turn to the Cretaceous and Tertiary floras of western America, as described by Lesquereux, Newberry, and others, we find in the lowest Cretaceous rocks there known—those of the Dakota group—which may be in the lower part of the Middle Cretaceous, a series of plants[EM] essentially similar to those of the so-called Upper Cretaceous of Greenland. They occur in beds indicating land and fresh-water conditions as prevalent at the time over great areas of the interior of America. But overlying this plant-bearing formation we have an oceanic limestone (the Niobrara), corresponding in many respects to the European chalk, and extending far north into the British territory,[EN] indicating that the land of the Lower Cretaceous was replaced by a vast Mediterranean Sea, filled with warm water from the equatorial currents, and not invaded by cold waters from the north. This is succeeded by thick Upper Cretaceous deposits of clay and sandstone, with marine remains, though very sparsely distributed; and these show that further subsidence or denudation in the north had opened a way for the arctic currents, killing out the warm-water animals of the Niobrara group, and rilling up the Mediterranean of that period. Of the flora of these Upper Cretaceous periods, which must have been very long, we know something in the interior regions, from the discovery of a somewhat rich flora in the Dunvegan beds of the Peace River district, on the northern shore of the great Cretaceous Mediterranean;[EO] and on the coast of British Columbia we have the remarkable Cretaceous coal-field of Vancouver Island, which holds the remains of plants of modern genera, and, indeed, of almost as modern aspect as those of the so-called Miocene of Greenland. They indicate, however, a warmer climate as then prevalent on the Pacific coast, and in this respect correspond with a peculiar transition flora, intermediate between the Cretaceous and Eocene or earliest Tertiary of the interior regions, and which is described by Lesquereux as the Lower Lignitic.
[EM] Lesquereux, “Report on Cretaceous Flora.”
[EN] G. M. Dawson, “Report on Forty-ninth Parallel.”
[EO] “Reports of Dr. G. M. Dawson, Geological Survey of Canada.” Also, “Transactions of the Royal Society of Canada,” vol. i.
Immediately above these Upper Cretaceous beds we have the great Lignite Tertiary of the West—the Laramie group of recent American reports—abounding in fossil plants, at one time regarded as Miocene, but now known to be Lower Eocene, though farther south extending upward toward the Miocene age.[EP] These beds, with their characteristic plants, have been traced into the British territory north of the forty-ninth parallel, and it has been shown that their fossils are identical with those of the McKenzie River valley, described by Heer as Miocene, and probably also with those of Alaska, referred to the same age.[EQ] Now this truly Eocene flora of the temperate and northern parts of America has so many species in common with that called Miocene in Greenland that its identity can scarcely be doubted. These facts have led to scepticism as to the Miocene age of the upper plant-bearing beds of Greenland, and more especially Mr. J. Starkie Gardner has ably argued, from comparison with the Eocene flora of England and other considerations, that they are really of that earlier date.[ER]