IX. ALTITUDE. 405 



coiTesponds rather closely with the lower flora of boreal 

 and arctic lands ; although it wants many of the arctic 

 species. And moreover the floral diversity above men- 

 tioned, as induced by the intermingling of other species 

 and genera, may be observed to some small extent on the 

 hills of Britain ; even on those of North Britain. The 

 mountain plants of Scotland, which botanical collectors 

 seek with so much eagerness under the designation of 

 ' alpines,' are mostly identical with species descending to 

 lower levels in more boreal lands. But several others of 

 the boreal species fail to reach the hills of Britain, though 

 found in Iceland or Faroe, and numerouslj'^ in Scan'dina- 

 via. And among those which do occur on the mountains 

 of North Britain, some very few in turn fail to reach the 

 more southerly masses of the Alps and Pyrenees ; for 

 example, Arenaiia 7'ubella, Saxifraga rivularis, Alopecurus 

 alpinus, &c. 



Moreover, among the arctic-alpines which are continued 

 southwards to the hills of Britain, other species are also 

 found which do not occur along with the proper arctics in 

 the low grounds of corresponding northern latitudes. In 

 example, Cherleria sedokles is a thoroughly alpine plant 

 in Scotland ; growing there only upon the mountains, 

 and among the truly arctic plants ; being absent from 

 Scandinavia, Russia, Siberia, North America ; but pre- 

 sent on the Alps, Pyrenees, and other European moun- 

 tains to the southward of Britain. Helianthemum canum 

 and Meconopsis camhrica in England and "Wales, and 

 Saxifraga umbrosa with its allied species in Ireland, sup- 

 ply somewhat similar illustrations from the more southei'n 

 and lower hills of the British islands. 



Probably on account of tlie decreased height and bulk 

 of the hills, as we pass southward in Britain, such illus- 

 trations are scanty in number ; so that a change in the 



VOL. IV. 3 o 



