330 MINNESOTA BOTANICAL STUDIES 



TABLE V. CERTAIN PLANTS OF THE LIMESTONE AREA AT THE HEAD OF 



DOWNIE CREEK 



Arabis Lyallii S. Wats. 



Asplenium viride Huds. 



Cryptogramma Stelleri (Gmel.) Prantl. Only recorded Selkirk station; 

 Rockies, "not common," Brown and Schaffer. 



Gentiana amarella L. var. acuta (Michx.) Herder. Only recorded Selkirk 

 station ; Rockies, very abundant. 



Lappula floribunda (Lehm.) Green. Nelson; Rockies, very abundant. 



Potentilla dissecta Pursh. "Small peak ;" the var. glaucophylla occurs on Ava- 

 lanche mt., Glacier, and Copperstain mt., Prairie Hills ; Rockies, both 

 forms are apparently common. 



Saxifraga punctata L. Asulkan valley ; Rockies, local. 



Saxifraga mertensiana Bong. Prairie Hills; Avalanche Crest, Glacier; Cougar 

 valley; Rockies (?). 



Shepherdia canadensis (L.) Nutt. Howser lake ; Gold stream, both at low 

 elevations ; the only station recorded well within the Selkirk range ; very 

 abundant in the Rockies, and in the low valleys bounding the Selkirk 

 range. 



Conclusion 



In the foregoing pages it has been shown that a considerable 

 number of plants which form characteristic parts of the Rocky 

 Mountain vegetation occur in the Selkirk range, some of them at 

 many widely separated points. These plants obviously have not 

 been historically unable to reach the Selkirks. Some of them, like 

 those occurring near the head of Downie creek, have penetrated 

 more than half-way across the range. The areas where they occur 

 have the typical Selkirk climate, and there is nothing about this 

 which interferes with their growth. Where they are found thev 

 are usually flourishing and bear an abundance of seeds. Apparently 

 the only explanation of their extremely local occurrence in the Sel- 

 kirks is the explanation put forth in section 1 of this paper, that 

 they require soils containing limestone, and that they grow with 

 great difficulty, or not at all, in its absence. The great abundance 

 of limestones in the Canadian Rocky mountains renders practi- 

 cally all the mixed soils of that range calcareous, and so allows 

 these plants to occur abundantly throughout the region. On the 

 other hand the characteristic Selkirk rocks are quartzites and schists 

 rich in quartz and very poor in lime.^ Many of the plants which 



1 Granite is exceptional, occurring in those parts of the range which are personally 

 known to the author, only in the region northwest of Mt. Sandford, and in Battle creek 

 valley, a little-known region about twenty-five miles south of Glacier. 



