54 DISTRIBUTION OF PLANTS 



distribution of plants in Britain, founded on Winch's 

 Sketch, before mentioned, and observations by the Rev. 

 J. Farquharson, of Alford, Aberdeenshire, on the heights 

 attained by different species (chiefly as cultivated plants) 

 in his vicinity. That district, however, is unfavourable 

 for ascertaining the true limits, and hence they are usually 

 given too low for the county in general, though doubtless 

 correct for the particular tract. 



IV. REMARKS ON THE DISTRIBUTION OF PLANTS 

 WITHIN BRITAIN. 



1. DISTRIBUTION IN ASCENDING REGIONS. 



If we compare the vegetation on the northern and 

 southern coasts of Britain, numerous species are seen on 

 the one which we may in vain seek on the other. If we 

 ascend the Highland mountains, before reaching their 

 summits nine tenths of the species observed at the base 

 have ceased to appear, and those which we still see are 

 dwarfed, depressed, usually flowerless, and appear as if 

 feebly struggling to maintain life; while other species, 

 never found on the plains, here flourish in their fullest 

 vigour. Bleak exposure, chilly climate, and clouded 

 atmosphere seem to be conditions chiefly operative in 

 effecting this change, gradually increasing from base to 

 summit. Hence the usual course with botanists is to 

 divide any country, the botanical aspect of which they 

 wish to delineate, into successive or ascending stages, 

 corresponding to such changes of climate and vegetation, 

 be they caused by latitude, by elevation, or by other con- 

 ditions affecting the growth of plants. But as no two 

 species have precisely the same line of cessation, all such 



