lxxiv BOTANY OF SOCOTRA. 



the small colony of plant-life on the Haghier Peaks, which probably were then 

 the only Socotran surface exposed. With the rising again of the land, and a 

 renewed connection with Africa and also with Asia, the union was of much 

 less extent, but of sufficient duration to allow of the inroad of a crowd of 

 north-east African and south-west Asian forms. 



We have, finally, to consider American affinities. The occurrence in Indian 

 Ocean islands of restricted new-world types, or of forms related to these, is a 

 remarkable and well-known fact of distribution. We have, for example, the 

 sapotaceous Labourdonnaisia represented in Natal, Mascarene Islands, and 

 Cuba ; the laurineous Ocotea with representatives in Canary Islands, South 

 Africa, and Madagascar, its main distribution being American ; and the Rodri- 

 guesian Mathurina, one of the TurneraceEe, with its nearest ally the central 

 American Erblichia. And now in Socotra we have similar relationships mani- 

 fested. I need only mention Thamnosma, Dirach?na, and Ccelocarpus. That 

 the identity of form means identity of stock is, I think, in many of these cases 

 an irresistible conclusion, but how the present distribution came about, whether 

 by migration from the south and west or from the north and east, is one of 

 those problems for which we have not yet the material for a solution. 



Such is the account of the characters and of the origin of the flora of 

 Socotra which I have the honour to submit to the Fellows of the Society. 



On page xxiii I have quoted the words of Professor Bonney, in which he 

 gives bis conclusions regarding the mutations of Socotra, based upon the geo- 

 logical evidence, and it will be seen that the botanical evidence entirely corro- 

 borates them. The zoological evidence is too imperfect to allow of historical 

 deductions being drawn from it, but in its several parts, as stated by the 

 zoologists whom I have quoted, it does not run counter to the evidence of the 

 plants. 



Dealing with the whole facts that are at command, I may give this brief 

 outline sketch of the geological and biological history of the island. During 

 the carboniferous epoch there was in the region of Socotra a shallow sea in 

 which was deposited on the top of the fundamental gneisses of this spot, which 

 had ere then been certainly much seamed and fractured by volcanic outbursts, 

 the sandstone of which we have such a large development in Nubia. This sea 

 subsequently deepened, allowing the formation of the shales, which now con- 

 stitute the argillite of the island. During the permian, Socotra may have been 

 a land-surface, forming part of the great mass of land which probably existed in 

 the region at that epoch, and gave the wide area for westward migration of life 

 which presently took place, and by which the eastern affinities in Socotra may be 

 explained. In early and middle tertiary times, when the Indian Peninsula was 

 an island, and the sea which stretched into Europe washed the base of the 

 Himalayan hills, Socotra was in great part submerged, and the great mass of its 



