Butters: plant distribution in the Selkirk mountains 331 



flourish on the somewhat sour soils formed by these rocks seem to 

 be largely inhibited by the presence of lime, and hence in the Rocky 

 mountains they are uncommon or absent, just as they are absent 

 from the limited limestone areas just discussed.^ The differences 

 then in the characteristic vegetation of the two ranges seem to be due 

 not only to the historical differences which undoubtedly occur,- and 

 to the climatic differences which also have considerable effect, but 

 also, and to a very large extent, to the great differences in the con- 

 stituent rocks of the two ranges, and in the soils which have been 

 derived from them. 



Similar instances have been noted many times in Europe, and 

 recently similar peculiarities in the distribution of the alpine plants 

 of eastern North America have been noted by Fernald.^ It is inter- 

 esting to note how regularly the distribution of plants as noted by 

 Fernald for New England and the region about the Gulf of St. 

 Lawrence agrees with the observations which have been made by 

 the author in the mountains of British Columbia, a portion of which 

 have been set forth in the present paper. Of 34 plants mentioned 

 both in the present paper, and by Fernald, 20 appear to have exactly 

 the same type of soil distribution in the two regions, the others 

 appear to be less particular in their soil requirements in one or the 

 other region. In no case is there a reversal of soil requirement as 

 between the two regions, and the same proportion holds good in the 

 case of the numerous other plants mentioned by Fernald and occur- 

 ring in the Rocky and Selkirk ranges, though not in the districts 

 covered by this paper. 



1 A number of them occur locally in the Rockies. The soils in which they are found 

 have not been tested, but their distribution suggests that they are found on the scattered 

 quartzite areas of that range, and that they therefore represent the converse of the peculiar 

 distributions discussed above. 



2 An interesting case of this is the total absence from the Selkirk range, so far as is 

 known, of the numerous species of Astragalus, Oxytropis, and Hedysarmn which' are 

 abundant in the Rockies. These plants would luidoubtedly grow well upon the calcareous 

 areas noted above, but with their poor means of migration they have been unable to reach 

 these small and isolated areas. 



3 M. L. Fernald, The Soil Preferences of Certain Alpine and Subalpine Plants: 

 Rhodora, 9:149, 1907. 



