PAKT I 



THE COXDITIO^^S OF YEGETATIOX IX 

 THE BRITISH ISLES 



CHAPTER I 



THE PHYSICAL CHABACTERS AXD CLIMATE OF THE 

 BRITISH ISLANDS 



The Britisli Islands stand on the "continental shelf" 

 of nortli-T.vestern Europe. The depth of the seas (English 

 Channel and Xorth Seaj separating them from the neigh- 

 bouring countries of the Continent nowhere reaches 200 

 metres and very rarely exceeds 100 metres. On the west 

 of Scotland and Ireland the floor of the Atlantic Ocean 

 slopes rapidly down to a depth of 2000 metres and in the 

 course of a few hundred miles depths of over 4000 metres 

 are reached. 



Thus the British Isles are physiographically simply 



^. ■, -^ ^ a slightly detached part of north-western 

 Similarity of a j r . 



flora and Europe, and their separation took place m 



vegetation to very recent geological times. This fact is 

 that of the reflected ia the flora, which is for the most 

 part identical with that of the adjacent parts 

 of the continent from which it is derived. 



FloristicaUy the British Isles are comparatively poor, 

 for many continental species fail to reach them, and they 



