III. FLORA OF BEITAIN. S87 



At the present time, within the limits of our own island, 

 plants appear to be extending northwardly, and con- 

 tracting their extension towards the south ; though chiefly 

 so, perhaps, through the instrumentality of mankind. 

 Whether any of them originally migrated into Britain in 

 the opposite direction, spreading from north to south, is 

 a questionable conjecture, not devoid of probability, but 

 supported by no botanical evidence, excepting the one 

 fact of identity between certain British and arctic or sub- 

 arctic species. The number of species common to Britain 

 and to countries more southward, is greater than the 

 number of species common to Britain and to countries 

 more northward. The floral resemblance, however, is 

 greater with the northern countries ; because these latter 

 commingle with them a less number of non- British 

 species. On this subject, the valuable writings of C. 

 Martins are well deserving of careful study. 



Regarding the British Isles collectively, the most dis- 

 tinctive peculiarities in their flora are found on the western 

 side. Thus, the Eriocaulon septangulare, a plant of Ire- 

 land and some of the westerly isles of Scotland, is con- 

 stantly cited as a remarkable exception to the prevailing 

 identity of the British flora with that of western Europe ; 

 since it belongs to a genus and order not otherwise repre- 

 sented in the European flora ; and the plant becomes a 

 constituent item in that flora only by its existence in the 

 British Isles. The Neottia gemmipara of Smith, an ex- 

 tremely local and scarce orchid of South Ireland, hitherto 

 has not been found in any other country ; as is now again 

 believed, although, some short time ago, it was supposed 

 to have been identified with the American Spiranthes cer- 

 niM. This orchid is the only plant allowed by Bentham's 

 Handbook, as an example of a species really restricted to 

 the British Isles, according to existing knowledge. [The 



