In the upper beds of the Upper Silurian, as has been already remarked, Lycopodites are the only terrestrial plants yet found. In the Lower Old Red Sandstone we find added to these, with Thallogens that bear at least the same _general_ character as in the system beneath, minute ferns, and a greatly larger plant, allied to the horse tails. The Old Red flora seems to have been prevailingly an acrogenic flora; and yet with almost its first beginnings,--contemporary with at least the earlier fossils of the system in Scotland, we find a true polycotyledonous tree, not lower in the scale than the araucarites of the Coal Measures,--which in structure it greatly resembles,--or than the pines or cedars of our own times (see Fig. 3). In the Middle Old Red Sandstone there occurs, with plants representative apparently of the ferns and their allies, a somewhat equivocal and doubtful organism, which may have been the panicle or compound fruit of some aquatic rush; while in the Upper Old Red, just ere the gorgeous flora of the Coal Measures began to be, there existed in considerable abundance a stately fern, the _Cyclopteris Hibernicus_ (see Fig. 2), of mayhap not smaller proportions than our monarch of the British ferns, _Osmunda regalis_, associated with a peculiar lepidodendron, and what seems to be a lepidostrobus,--possibly the fructiferous spike or cone of the latter, mingled with carbonaceous stems, which, in the simplicity of their texture, and their abundance, give evidence of a low but not scanty vegetation. Ere passing to the luxuriant carboniferous flora, I shall make but one other remark. The existing plants whence we derive our analogies in dealing with the vegetation of this early period, contribute but little, if at all, to the support of animal life. The ferns and their allies remain untouched by the grazing animals. Our native club mosses, though once used in medicine, are positively deleterious; the horse tails, though harmless, so abound in silex, which wraps them round with a cuticle of stone, that they are rarely cropped by cattle; while the thickets of fern which cover our hill-sides, and seem so temptingly rich and green in their season, scarce support the existence of a single creature, and remain untouched in stem and leaf, from their first appearance in spring, until they droop and wither under the frosts of early winter. Even the insects that infest the herbaria of the botanist almost never injure his ferns. Nor are our resin-producing conifers, though they nourish a few beetles, favorites with the herbivorous tribes in a much greater degree. Judging from all we yet know, the earliest terrestrial flora may have covered the dry land with its mantle of cheerful green, and served its general purposes, chemical and others, in the well-balanced economy of nature; but the herb-eating animals would have fared but ill even where it throve most luxuriantly; and it seems to harmonize with the fact of its