more equivocal productions of the Coal Measures are represented by what seems to be the last of the Calamites; but it contains no Lepidodendra—no Ulodendra—no Sigillaria—no Favularia—no Knorria or Halonia. Those monsters of the vegetable world that united to the forms of its humbler productions the bulk of trees, had, with the solitary exception of the Calamites, passed into extinction; and ere the close of the system they too had disappeared. The forms borne by most of the Oolitic plants were comparatively familiar forms. With the Acrogens and Gymnogens we find the first indication of the Liliaceæ, or lily-like plants—of plants, too, allied to the Pandanaceæ or screw pines, the fruits of which are sometimes preserved in a wonderfully perfect state of keeping in the Inferior Oolite, together with Carpolithes—palm-like fruits, very ornately sculptured—and the remains of at least one other monocotyledon, that bears the somewhat general name of an Endogenite. With these there occur a few disputed leaves, which I must persist in regarding as dicotyledonous. But they formed, whatever their true character, a very inconspicuous feature in the Oolitic flora; and not until the overlying Cretaceous System is ushered in do we find leaves in any considerable quantity decidedly of this high family; nor until we enter into the earlier Tertiaries do we succeed in detecting a true dicotyledonous tree. On such an amount of observation is this order of succession determined—though the evidence is, of course, mainly negative—that when, some eight or ten years ago, Dr. John Wilson, the learned Free Church missionary to the Parsees of India, submitted to me specimens of fossil woods which he had picked up in the Egyptian Desert, in order that I might if possible determine their age, I told him, ere yet the optical lapidary had prepared them for examination, that if they exhibited the coniferous structure, they might belong to any geologic period from the times of the Lower Old Red Sandstone downwards; but that if they manifested in their tissue the dicotyledonous character, they could not be older than the times of the Tertiary. On submitting them in thin slices to the microscope, they were found to exhibit the peculiar dicotyledonous structure as strongly as the oak or chestnut. And Lieutenant Newbold's researches in the deposit in which they occur has since demonstrated, on stratigraphical evidence, that not only does it belong to the great Tertiary division, but also to one of the comparatively modern formations of the Tertiary.
Fig. 38
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Fig. 39. |
Fig. 40. |
| (Reduced one third.) | |
Fig. 41.
Fig. 42.
Fig. 43.
The earlier flora of this Tertiary division presents an aspect widely different from that of any of the previous ones. The ferns and their allies sink into their existing proportions; nor do the coniferæ, previously so abundant, occupy any longer a prominent place. On the other hand, the dicotyledonous herbs and trees, previously so inconspicuous in creation, are largely developed. Trees of those Amentiferous orders to which the oak, the hazel, the beech, and the plane belong, were perhaps not less abundant in the Eocene woods than in those of the present time: they were mingled with trees of the Laurel, the Leguminous, and the Anonaceous or custard apple families, with many others; and deep forests, in the latitude of London (in which the intertropical forms must now be protected, as in the Crystal Palace, with coverings of glass, and warmed by artificial heat), abounded in graceful palms. Mr. Bowerbank found in the London clay of the island of Sheppey alone the fruits of no fewer than thirteen different species of this picturesque family, which lends so peculiar a feature to the landscapes in which it occurs; and ascertained that the undergrowth beneath was composed, in large proportion, of creeping plants of the gourd and melon order. From the middle or Miocene flora of the Tertiary division—of which we seem to possess in Britain only the small but interesting fragment detected by his Grace the Duke of Argyll among the trap-beds of Mull—most of the more exotic forms seem to have been excluded. The palms, however, still survive in no fewer than thirty-one different species, and we find in great abundance, in the place of the other exotics, remains of the plane and buckthorn families—part of a group of plants that in their general aspect, as shown in the Tertiary deposits of the Continent, not a little resembled the vegetation of the United States at the present day. The nearer we approach to existing times, the more familiar in form and outline do the herbs and trees become. We detect, as has been shown, at least one existing order in the ferns of the Coal Measures; we detect at least existing genera among the Coniferæ, Equisetaceæ, and Cycadaceæ of the Oolite; the acacias, gourds, and laurels of the Eocene flora, and the planes, willows, and buckthorns of the Miocene, though we fail to identify their species with aught that now lives, still more strongly remind us of the recent productions of our forests or conservatories; and, on entering, in our downward course, the Pleistocene period, we at length find ourselves among familiar species. On old terrestrial surfaces, that date before the times of the glacial period, and underlie the boulder clay, the remains of forests of oak, birch, hazel, and fir have been detected—all of the familiar species indigenous to the country, and which still flourish in our native woods. And it was held by the late Professor Edward Forbes, that the most ancient of his five existing British floras—that which occurs in the south-west of Ireland, and corresponds with the flora of the northwest of Spain and the Pyrenees—had been introduced into the country as early, perhaps, as the times of the Miocene. Be this, however, as it may, there can rest no doubt on the great antiquity of the prevailing trees of our indigenous forests.
The oak, the birch, the hazel, the Scotch fir, all lived, I repeat, in what is now Britain, ere the last great depression of the land. The gigantic northern elephant and rhinoceros, extinct for untold ages, forced their way through their tangled branches; and the British tiger and hyæna harbored in their thickets. Cuvier framed an argument for the fixity of species on the fact that the birds and beasts embalmed in the catacombs were identical in every respect with the animals of the same kinds that live now. But what, it has been asked, was a brief period of three thousand years, compared with the geologic ages? or how could any such argument be founded on a basis so little extended? It is, however, to no such narrow basis we can refer in the case of these woods. All human history is comprised in the nearer corner of the immense period which they measure out; and yet, from their first appearance in creation till now they have not altered a single fibre. And such, on this point, is the invariable testimony of Palæontologic science—testimony so invariable, that no great Palæontologist was ever yet an asserter of the development hypothesis. With the existing trees of our indigenous woods it is probable that in even these early times a considerable portion of the herbs of our recent flora would have been associated, though their remains, less fitted for preservation, have failed to leave distinct trace behind them. We at least know generally, that with each succeeding period there appeared a more extensively useful and various vegetation than that which had gone before. I have already referred to the sombre, unproductive character of the earliest terrestrial flora with which we are acquainted. It was a flora unfitted, apparently, for the support of either graminivorous bird or herbivorous quadruped. The singularly profuse vegetation of the Coal Measures was, with all its wild luxuriance, of a resembling cast. So far as appears, neither flock nor herd could have lived on its greenest and richest plains; nor does even the flora of the Oolite seem to have been in the least suited for the purposes of the shepherd or herdsman. Not until we enter on the Tertiary periods do we
