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 

 wdiich 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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