16 Physical Characters of the British Isles 



have few, if any, endemic species\ Their isolation has 

 not been sufficiently prolonged nor are their climatic 

 conditions sufficiently distinct for the evolution of a dis- 

 tinctive flora. The most interesting floristio groups are 

 certain species confined to the east and south-east, which 

 are mid-European forms not found in northern Europe ; the 

 " arctic-alpine " species of the Scottish mountains, of which 

 a few occur also on the mountains of northern England, 

 North Wales and Ireland ; the species confined to Ireland 

 and south-west England, some of which are found in 

 western France, while others (notably Arbutus Unedo) are 

 Iberian or Mediterranean plants ; and finally a small group 

 of American species found in Ireland. It will be seen 

 that all these groups are simply extensions (occasionally 

 discontinuous extensions) of continental floras to the 

 nearest parts of the British Isles. Into the question of 

 their mode of migration we cannot enter here. 



With regard to vegetation too, it is doubtful if we 

 have any plant-formations unrepresented on the Continent, 

 though it is impossible to be certain till a more systematic 

 comparison has been made. 



In spite of their comparatively small size the British 

 Isles show a considerable variety of physio- 

 eo ogy and graphical features corresponding with the 

 orography. , • • j- i • i ,. 



very extensive series of geological formations 



represented. 



Considering the island of G-reat Britain (Scotland, 

 England and Wales) alone it may be said that the older 

 and harder (Palasozoic and metamorphio) rocks, forming 



1 i.e. species in the aggregate sense ; in the last (10th) edition (1908) 

 of The London Catalogue of British Plants there are however about 

 30 species and 100 varieties of flowering-plants and ferns, exclusive of 

 the genera Rubus and Hieracium, described by modern British sys- 

 tematists and not recorded from other countries. Besides these there 

 are about 30 "endemic" Mubi and 70 "endemic" (mainly arotic-alpiue) 

 Hieracia. 



