CHAP, xxiii.] ARCTIC PLANTS IN NEW ZEALAND. 



48D 



Isthmus of Panama, where there is 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 diftusion of plants ; 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. Con- 

 sidering 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 we 

 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 belov/ them. 



Now, just as these numerous species and genera have un- 

 doubtedly passed along the great 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 Aus- 

 tralia 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 



