ciiAr. xxiii.] ARCTIC PLANTS IN NEW ZEALAND. 
489 
Isthmus of Panama, where there is a distance of about 300 
miles occupied by rugged forest-clad hills, between the lofty 
peaks of Yeragua and the northern extremity of the Andes of 
New Grenada. Such distances are, as we have already seen, 
no barrier to the diffusion 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 below 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 
