CHAP. XXIII ARCTIC PLANTS IN NEW ZEALAND 521 



a distance of about 300 miles occupied by rugged forest- 

 clad hills, between the lofty peaks of Veragua and the 

 northern extremity of the Andes of New Grenada. Such 

 distances are, as we have already seen, no barrier to the 

 diffusion of j^lants ; and we should accordingly expect that 

 this- great continuous mountain-chain has formed the most 

 effective agent in aiding the southward migration of the 

 Arctic and north temperate vegetation. We do find, in 

 fact, not only that a large number of northern genera and 

 many species are scattered all along this line of route, but 

 that at the end of the long journey, in Southern Chile and 

 Fuegia, they have established themselves in such numbers 

 as to form an important part of the flora of those countries. 

 From the lists given in the works already referred to, it 

 appears that there are between sixty and seventy northern 

 genera in Fuegia and Southern Chile, while about forty of 

 the species are absolutely identical with those of Europe 

 and the Arctic regions. Considering how comparatively 

 little the mountains of South Temperate America are yet 

 known, this is a very remarkable result, and it proves 

 that the transmission of species must have gone on up to 

 comparatively recent times. Yet, as only a few of these 

 species are now found along the line of migration, we see 

 that they only occupied such stations temporarily ; and Ave 

 may connect their disappearance with the passing away of 

 the last glacial period which, by raising the snow-line, 

 reduced the area on which alone they could exist, and 

 exposed them to the competition of indigenous plants from 

 the belt of country immediately below them. 



Now, j list as these numerous species and genera have 

 undoubtedly passed along the gTeat American range of 

 mountains, although only now found at its two extremes, 

 so others have doubtless passed on further; and have 

 found more suitable stations or less severe competition in 

 the Antarctic continent and islands, in New Zealand, in 

 Tasmania, and even in Australia itself. The route by 

 which they may have reached these countries is easily 

 marked out. Immediately south of Cape Horn, at a 

 distance of only 500 miles, are the South Shetland Islands 

 and Graham's Land, whence the Antarctic continent or a 



