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