of the great Silurian period, as exhibited in the rocks, from the base to nearly the top of the system. And should we add to the rocky tract, rich in fucoids, a submarine meadow of pale shell sand, covered by a deep green swathe of zostera, with its jointed saccharine roots and slim flowers, unfurnished with petals, we would render it perhaps more adequately representative still.

We cross the beach, and enter on a bare brown moor, comparatively fertile, however, in the club mosses. One of the largest and finest of the species, Lycopodium clavatum, with its long scaly stems and upright spikes of lighter green, altogether a graceful though flowerless plant, which the herd-boy learns to select from among its fellows, and to bind round his cap,goes trailing on the drier spots for many feet over the soil; while at the edge of trickling runnel or

marshy hollow, a smaller and less hardy species, Lycopodium inundatum, takes its place. The marshes themselves bristle thick with the deep green horse tail, Equisetum

fluviatile, with its fluted stem and verticillate series of linear branches. Two other species of the same genus, Equisetum sylvaticum and Equisetum arvense, flourish on the drier parts of the moor, blent with two species of minute ferns, the moonwort and the adder's tongue, ferns that, like the magnificent royal fern (Osmunda regalis), though on a much humbler scale, bear their seed cases on independent stems, and were much sought after of old for imaginary virtues, which the modern schools of medicine refuse to recognize. Higher up the moor, ferns of ampler size occur, and what seems to be rushes, which bear atop conglobate panicles on their smooth leafless stems; but at its lower edge little else appears than the higher Acrogens, - ferns and their allies. There occurs, however, just beyond the first group of club mosses, a remarkable exception in a solitary pine, the advance guard of one of the ancient

forests of the country, which may be seen far in the background, clothing with its shaggy covering of deep green the lower hill-slopes. And as we found in the Thallogens of

that littoral zone over which we have just passed, representatives of the marine flora of the Silurian System, from the first appearance of organisms in its nether beds, to its bonebed of the Upper Ludlow rocks, in which the Lycopodites first appear, so in the Acrogens of that moor, with its solitary coniferous tree, we may recognize an equally striking representative of the terrestrial flora which existed during the deposition of these Ludlow rocks, and of the various formations of the Old Red Sandstone, Lower, Middle, and Upper.

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 carbona

ceous 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 dele

terious; 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 non-edible character, that up to the present time we know not that a single herbivorous animal