Affınities: Marine Flora; Liverworts, 313 
No fewer than 184 of the 379 arctic east American species (fully half) are 
absent in west Greenland, whilst only 105 (much less than one-third) are absent 
in Europe. Of the 379 arctic east American species only 56 are not found 
in temperate east America, of which two are absolutely confined to this area; 
two others, Parrya arenicola and Festuca Richardsoni, to arctic east and west 
America; 25 are found in temperate west America, and about 20 are Rocky 
Mountain species, and not found elsewhere in temperate America. 
Algae. The strong endemism of the purely arctic marine flora points 
to it as no immigrant flora, but one that possesses its center of development 
in the Arctic Sea. Other circumstances lead cogently to the same conclusion, 
indicating at the same time that the present purely glacial marine flora must 
have been formerly more widely spread towards the south than it is now. 
This results from a comparison of the flora of the Arctic Sea with that of 
the northern Atlantic and the northern Pacific. The Arctic Sea possesses 
184 species in common with the North Atlantic and only ıı of these species 
are exclusively American, for by far the greater number occur on the Atlantic 
coasts of Europe according to KJELLMAN'). The present flora in the northern 
part of the Pacific differs so essentially in composition from that of the 
northern Atlantic, that is to say, it contains many species that are so sharply 
distinguished from those of the Atlantic, even belonging to quite different 
types, that in order to account in any way for this fact, one is necessarily 
obliged to assume that these two divisions of the ocean appertain to different 
areas of development within which different forms have continued to be evolved 
during a very long time. (Confer Phyllospadix: Fig. ıı, p. 314.) However, 
on the other hand, it is a well known fact that the northern Atlantic has no 
inconsiderable number of species in common with the northern Pacific. 
Comparison of North Temperate and Arctic Liverworts. In the north tem- 
perate and arctic zones, according to UNDERWOOD*) (1892), there are known 
about 575 species of liverworts, Musci hepaticae. Of these 375 belong to the 
flora of Europe, 300 to that of America, and perhaps ı50 to that of Asia. 
Of these, we may take, as representing the boreal and sub-boreal portions, 
173 species for northern Europe, 163 for northern America, and 98 species 
for northern Asia. Of the 214 boreal and sub-boreal species, eighty per cent 
are European, seventy-six per cent are American, and forty-six per cent are 
Asiatic. While the larger part of the species of Europe and America have 
been brought to light, it is quite likely that the smaller number known from 
the more extensive Asiatic continent is due to the limited exploration of that 
region. Of the 163 American species, 129 or seventy-eight per cent are of 
the European flora; 69 are also Asiatic, while 32, or twenty per cent, are 
endemic. 
1) KjELLman, F.R.: The Algae of the Arctic Sea. 50. 1883. 
2) UnDerwoop, Lucien M.: A preliminary Comparison of the hepatic Flora of boreal and 
sub-boreal Regions, Botanical Gazette XVII: 305. October 1892. 
