484 X. GENERAL EEMARKS. 



southern hills, the more boreal would become their flora 

 at the upper stages of height. But it has been insisted 

 that this general notion requires limitation ; that it be- 

 comes less strictly true and applicable, as the latitudinal 

 distance increases ; the floras of the higher montane zones 

 becoming less identical with the floras of far boreal lati- 

 tudes, as the distance between them increases. 



Within the area of this island, however, it is found suf- 

 ficiently possible to trace out certain zones of plants under 

 the joint influence of latitude and elevation, modified 

 somewhat by other conditions. The plants absent from 

 the open country of South England, and which first ap- 

 pear about or above the bases of the hills of Wales and 

 North England, are again met with on the northern coasts 

 of Scotland, or inland in the lowest mountain valleys 

 there. Those which occur higher up on the hills of South 

 and Mid Britain, are again found on the mountains of 

 North Britain ; usually commencing there at lower levels 

 than they descended to in England or Wales. And the 

 uj)per zones of the plants on the Highland mountains, 

 though unrejjresented on the coast-level in this island, 

 have a considerable floral identity with more boreal and 

 arctic lands. As a general example, the flora of the mid- 

 arctic zone in Britain may be said to occur on the coast- 

 level in Iceland and other sub-arctic lands ; and that 

 of the superarctic zone is partially repeated at the coast- 

 level in Spitzbergen and other sub-polar lands. 



The floral identity is far from comi)lete ; considerable 

 diversity of species being also found between any levels 

 and latitudes so compared. Nor do the same species 

 cease in the same relative order or sequence in successive 

 stages of boreal latitude, as they do in successive stages 

 of height on the mountain acclivities. If we should 

 observe species a b c d e f ceasing in succession at 



