298 Canadian Record of Science. 



well-watered slopes, though not abundant in this part 

 of the Columbia-Kootanie Valley, is the western "cedar" 

 or arbor-vitse (Thuya gig anted). Its absence in the eastern 

 valleys is probably due to the want of a sufficiently moist 

 atmosphere rather than to the somewhat more rigorous 

 climate. Lyall's larch (Larix Lyallii) forms an open fringe 

 along the upper limit of forest growth in these moun- 

 tains, or at about Y000 feet, above which arboreal vege- 

 tation is scarcely observed. When the leaves of this 

 little larch become yellow, in September, its zone of growth 

 may often be traced, from a distance, with the regularity of 

 a contour-line. 



Leaving out of consideration the arbor-vitae, which, as 

 before stated, affects a peculiar station, together with other 

 trees of rarer occurrence, the common conifers may be 

 arranged in a regular series from those tolerant of the 

 most alpine conditions to those which require a high degree 

 of summer heat combined with a dry atmosphere, as 

 follows : — 



Larix Lyallii. Strictly alpine. 



Abies subalpina. Alpine and sub-alpine and extending to 

 high and cool valleys on both slopes. 



Picea Engelmanii. Sub-alpine and extending downward 

 wherever the soil is sufficiently moist, on both slopes. 



Pseudotsuga Louglasii. Lower valleys on both slopes. 



Larix occidentalis. Base of Mountains on west slope only. 



Pinus ponder osa. Base of mountains on west slope only. 



Prof. Macoun has made extensive collections of plants in 

 the mountains adjacent to the railway line, and it may be 

 of interest from a botanical point of view to note his 

 observation that a number of mountain plants obtained by 

 myself in the southern part of the region, appear to reach 

 their northern limit there, and do not recur even in the 

 high mountains in the vicinity of the Bow and Kicking 

 Horse valleys. This circumstance is doubtless in connection 

 with the partial break in the continuity of the higher 

 ranges about the head-waters of the Old Man Eiver, and 

 the species wanting are probably those which require 

 relatively dry as well as alpine conditions. 



