they have been conveyed as seeds through the air; for besides the un- portant fact that they are all members of families having seeds not well adapted for such diffusion, and that the species of Compositæ and other plants with winged seeds associated with them in Spain are not present with them in Ireland, it would be very extraordinary if the winds which had conveyed them so far, had never, through, probably a long series of centuries, conveyed them still further, and diffused them in a country where there are abundance of situations well adapted for their habitation. The hypothesis, then, which I offer to account for this remarkable flora is this—that at an ancient period, an epoch anterior to that of any of the floras we have already considered, there was a geological union or close approximation of the west of Ireland with the north of Spain; that the flora of the intermediate land was a continuation of the flora of the Peninsula; that the northernmost bound of that flora was probably in the line of the western region of Ireland; that the destruction of the intermediate land had taken place before the Glacial period; and that, during the last-named period, climatal changes destroyed the mass of this southern flora remaining in Ireland, the survivors being such species as were most hardy, saxifrages, heaths, such plants as Arabis ciliata and Pinguicula grandiflora, which are now the only relics of the most ancient of our island floras.
This, I admit, is a startiing proposition, and demands great geological operations to bring about the required phenomena. With such a gulf as now intervenes between Ireland and Asturias it may seem fanciful and daring to suppose their union within the epoch of the existence of the plants now living in both countries. What then are the geological probabilities of the question?
During the epoch of the deposition of the miocene tertiaries there was sea—probably shallow—inhabited by an assemblage, almost uniform, of marine animals throughout the Mediterranean region (tertiaries of Cerigo, Candia, Malta, Corsica, Malaga, Algiers), across the south of France (Montpellier, Bordeaux), along the west of the Peninsula (Lisbon, &c.), and in the Azores (St. Mary's). I speak to the uniform zoological character of this sea from personal examination of its fossils. During the miocene epoch, then, we can suppose no union of Asturias and Ireland. But at the close of the miocene epoch great geological operations took place: witness the miocene marine beds discovered by Lieut. Spratt and myself at elevations from 2 to 6,000 feet in the Lycian Taurus. The whole of the bed of this great miocene sea appears to have been in the central Mediterranean and west of Europe pretty uniformly elevated. This then could—with every probability—have been the epoch of the connexion or approximation of Ireland and Spain. My own belief is, that a great miocene land, bearing the peculiar flora and fauna
