The Origin of our British Flora 
Rocky Mountains and the Andes (Luzula spicata, 
Cerastium alpinum). 
The clearest idea that one can obtain therefore from 
recent researches is that of a huge Northern Drift over- 
shadowing the northern hemisphere, and dividing off 
groups of separate mountain chains, so producing an 
infinity of subtropical, temperate, and cold climates, all 
separated from each other, and in each of which the 
formation of new species was proceeding rapidly. 
The Spanish peninsula seems to have been specially 
isolated, and in consequence we find its flora to-day 
very rich in peculiar or endemic species, For the 
British islands the problems are not nearly so complex 
as for Europe generally. There are some four or five 
American-Irish plants and, chiefly in the extreme south 
of England, the Cornish heath, and a few others which 
are allied to the Portuguese-Spanish flora. But the 
British flora, as a whole, is the north temperate 
European flora. 
When the Ice Age began to vanish away, when 
glaciers shrunk, and when the accumulated snowfields 
of centuries dissipated themselves in those awful floods 
which have filled some valleys with hundreds of feet of 
shingle and of sand, the process of re-occupation must 
have been very slow and tedious. 
It is quite possible that in Southern England the 
vegetation had never been entirely destroyed, but in 
Scotland and Northern England it was only upon some 
black “ nunatak” or projecting rocky mountain of high 
altitude that a few miserable alpines might have survived. 
One has only to trace the course of the boulder-clay 
in order to see how utterly all vegetation worth the name 
must have been swept away. It was a new bare country 
which the first post-glacial plants set about occupying 
and developing. 
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