330 THE CANADIAN NATURALIST. [June 



more Scandinavian species would return to Arctic America and 

 Asia than survived in Greenland ; some would be changed in form, 

 because only the favoured varieties could have survived the struggle ; 

 some of the species of Alpine Siberia and of the Rocky Mountains 

 would accompany the Scandinavian in their return to the arctic 

 zone ; while many arctic species would ascend those mountains, 

 accompanying the alpine species in their reascent. 



Again, as the same species may have been destroyed in many 

 longitudes, or at most elevations, but not at all, we should expect 

 to find some of those Arctic Scandinavian plants of Greenland 

 which have not returned to Arctic America still lurking in remote 

 corners of that great continent; and we may account for Drdba 

 aurea being confined to Greenland and the Rocky Mountains, 

 Potentilla tridentatato Greenland and some scattered localities from 

 the Alleghanies northward, and Arenarta Grmdandlca to 

 Greenland, Labrador and the Mountains of New England, by sup- 

 posing that these were originally Scandinavian plants, which were 

 driven south by the cold of the glacial epoch, but which on the return 

 of warmth, being exterminated on the plains of the American con- 

 tinent, found a refuge among its mountains, where they now exist. 



It appears, therefore, to be no slight confirmation of the general 

 truth of Mr. Darwin's hypothesis, that, besides harmonizing with 

 the distribution of arctic plants within and beyond the polar zone, 

 it can also be made, without straining, to account for that distribu- 

 tion and for many anomalies of the Greenland flora, viz., i. — its 

 identity with the Lapponian ; ii. — its paucity of species; iii. — the 

 fewness of temperate plants in temperate Greenland, and the still 

 fewer plants that area adds to the entire flora of Greenland ; 

 iv. — the rarity of both Asiatic and American species or types in 

 Greenland ; and v. — the presence of a few of the rarest Greenland 

 and Scandinavian species in remote and often alpine localities of 

 West America and the United States. 



I. — ON THE LOCAL DISTRIBUTION OF PLANTS WITHIN 

 THE ARCTIC CIRCLE. 



The greatest number of plants occurring in any given arctic 

 district is found in the European, where 616 flowering plants 

 have been collected from the verge of the circle to Spitzbergen. 

 From this region vegetation rapidly diminishes in proceeding east- 

 wards and westwards, especially the latter. Thus, in Arctic Asia 

 only 233 flowering plants have been collected ; in Arctic Green- 



