OF THE PE11UYIA:N- ANDES. 23 



to impress itself upon my memory when originally presented to 

 it, and I further find that the same view has since been defended 

 by Mr, Wallace in his remarkable work on ' Island Life/ and 

 still more recently by Professor Eugler. If I have rightly ap- 

 prehended the brief statement of his views given by Mr. Wallace 

 in pages 489 and 490 of tlie work aboA^e cited, they do not com- 

 pletely accord with the conception that seems to me best to 

 account for ascertained facts ; and I may here specify the j)oints 

 of diiFerence. Mr. Wallace regards the peopling of the Antarctic 

 lands with their characteristic generic types as a comparatively 

 recent event. He supposes that those already existing types 

 were carried southward from South America, or other circum- 

 polar countries, to a preglacial Antarctic continental region, and 

 having there spread widely, were thence conveyed northward to 

 the widely scattered islands where they still survive. To me it 

 seems much more probable that the origin of the special generic 

 types of the Antarctic flora should be referred to the Antarctic 

 region itself. They belong, without exception, to the great 

 groups or natural orders which are now almost universally 

 diffused throughout the world j and the ancestral types from 

 which they originated were probably carried to that region at a 

 remote period when the physical conditions of the earth's surface 

 were widely different from those now prevailing. Their present 

 distribution points rather to migration from a higher latitude to 

 their present homes, than to transport in an opposite direction. 

 On large continents where no barriers, such as wide deserts or 

 high mountain-chains, intervene, the diffusion of plants occurs 

 most easily in directions between east and west, because the 

 climatal conditions are more nearly uniform. But the reverse 

 obtains where the transport takes place across wide spaces of 

 ocean. The two chief agents are ocean-currents, with or without 

 floating ice, and migratory birds ; and, speaking generally, the 

 predominant direction in which these travel approaches to the 



meridians of longitude. 



I may here venture to express the belief that the efficacy of 

 winds as agents for the dispersal of plants over wide ocean spaces 

 has been considerably overrated. We know that the spores of 

 cryptogams may be conveyed for indefinite distances by aerial 

 currents ; but the seeds of flowering plants are immeasurably 

 heavier; and I am not aware of a single fact that authorizes us 

 to infer that mode of transport over wide intervals of ocean as 



