CONDITIONS ON WHICH DISTRIBUTION DEPEND. 57 
to 55. France is therefore unquestionably richer in species 
than Lapland. 
‘But the matter stands in a somewhat different light 
when we consider these plants in relation to the total 
vegetation of the two countries; and since it is by this 
means we come to comprehend the characteristic of the 
region of vegetation, we can only allow this mode of consid- 
eration tu be valid. Now France possesses altogether about 
4,500 planerogamous plants, and the sedges constitute only 
1-27th of these; the phanerogamia of Lapland are confined 
to some 500 species, and 1-9th of these are sedges. The 
sedges are therefore a much more essential part of the 
Lapponic flora than of the French, the former baving a 
relatively larger number of species than the latter. And 
this it is alone that is understood by the increase ‘of 
species in a given direction.’ 
