of the Distribiaion of Arctic Plants, 337 



ment and diversity thereby. Considering the present frigid climate 

 of Greenland, the isotherm of 32° just impinging upon its south- 

 ern point, its moderate summer and low autumnal temperature, 

 we should rather have supposed the complete extermination of 

 the Greenland ante-glacial flora ; and have referred the Scandi- 

 navian character of the existing flora (all but eleven of the 207 

 arctic species, and almost all those of temperate Greenland, being 

 European plants,) directly to subsequent immigration from the 

 eastern continent. Several geographical considerations, and the 

 course of the currents, which Dr. Hooker brings to view on p. 

 270, would go far towards explaining why Greenland should have 

 been re-peopled from the Old rather than from the New World. 

 While the list (on p. 272, 273) of upwards of 230 Arctic Euro- 

 pean species which are all likewise American plants, but are re- 

 markable for their absence from Greenland, would indicate no 

 small difficulty in the westward migration, and render it most 

 probable that thedifi'usion of species from the Old World to thp 

 New was eastward through Asia, for the arctic no less than (as 

 has elsewhere been shown) for the temperate plants. Was it that 

 Greenland and the adjacent part of the American continent remain- 

 ed glacial longer than the rest of the zone ? And if our northern 

 regions were thus colonized by an ancient Scandinavian flora, this 

 seems to have been in return for a still earlier donation of Ame- 

 rican plants to Europe, to which a very few existing but nume- 

 rous fossil remains bear testimony. Speculative inquiries of this 

 sort are enticing, and the time is approaching in which they ma^ 

 be fruitful.' 



* Indeed, the characteristic features and the immediate interest 

 and importance of the present memoir, as of others of the same 

 general scope and interest, are found in this : 1. That the actual 

 geographical distribution of species is something to be accounted 

 for; 2. That our existing species, or their originals, are far more 

 ancient than was formerly thought, mainly if not wholly antedat- 

 ing the glacial period; and, 3. That they have therefore been sub- 

 ject to grave climatic vicissitudes and changes. There may be many 

 naturalists who still hesitate to accept these propositions, as there 

 as one or two who deny them; but these or similar conclusions 

 have evidently been reached by those botanists, paleontoloo-jsts 

 and geologists in general who have most turned their thouo-hta 

 to such enquiries, and who march foremost in the advancino- move- 

 ment of these sciences. In this position, the author of the 

 Can. Nat. 22 Vol. Yll 



