ae Cincinnati Society of Natural History. 
when S. langsdorffit lived there.* Innumerable herbaceous species, 
too, found suitable homes in the forests and plains of the north at that 
time ; and as the same species of plants live to a greater or less ex- 
tent all around the’ Arctic circle at the present day, there is no reason 
to suppose it was otherwise then. 
With all this luxuriant vegetation at the North Pole, let us suppose 
the cold period to begin. Such species as were capable of so doing, 
gradually worked their way further and further from the land of their 
birth, driven by the increasing cold of each successive year. If we 
suppose a distance of 600 miles to separate two groups of one species 
at 80° of latitude, and suppose they migrated in a direct line south, 
we find that when latitude 50° was reached, no less than 2,700 
miles would separate species and descendants of individuals which ~ 
had been before living near together. Or if a species had lived at the 
Pole, and some individuals had gone one way, and some the opposite, 
when their descendants reached temperate regions, we would find them 
on opposite sides of the globe, without, perhaps, being found in inter- 
mediate localities. 
The remarkable fact that some species of plants of the Arctic 
regions and of Europe, are identical with some found on the Chilian 
Andes, the Antarctic Islands, in Australia and New Zealand, can be 
explained on the same theory. The Rocky Mountains and the Andes 
form a highway which would facilitate the passage of various species. 
And when the Arctic forms were forced south by the cold of the 
glacial epoch, the mountains of the Andes would take them to or 
beyond the equatorial regions, and furnish them homes until the cold 
commenced in the Southern hemisphere. Then they would descend 
to the plains, mingle with the forms from the Antarctic regions, and 
finally take up their abode at the extreme southern end of the conti- 
nent. 
There is, doubtless, a considerable area of land around the South 
Pole, and if the theory of glacial and interglacial (warm) periods be 
a correct one : and if the Antarctic seas and continents were at times 
free from ice and snow, and enjoyed a climate similar to that which 
temperate regions now have, the similarity which has been notedf be- 
tween the Alpine floras of the South American Andes and New Zea- 
land, will be explained. ‘The lower end of the American continent is 
not so very far away from New Zealand if we take the distance in a 
* Croll, Climate and Time, p. 310. 
+ Hooker Intro. Essay to Flora of New Zealand, p. xxiy. 
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