POKEST ZONES AND FORMATIONS 



97 



Table 20. Ranges in Altitude. 



The wide range in altitude of the species here indicated and 

 the fact that at all elevations between 4000 and 6000 feet, within 

 their range and habitat they are likely to be intermingled makes 

 difficult the distinction between the Canadian and Hudsonian 

 zones, or the montane and sub-alpine, if indeed there is any in 

 this region. The term sub-alpine, when used herein, is intended 

 to designate the forests immediately below the higher crests. 

 The trees of this belt, however, have few species which do not 

 descend to the foothills. The alpine fir, Abies lasiocarpa, is the 

 most conspicuous tree at high elevations, but is commonly found 

 in the canyons about IMissoula at about 4000 feet and descends 

 at least to 2000 feet along the Kootenai in Montana. The same 

 may be said for the Engelmann spruce. The white bark pine, 

 (P albicaidis) also a common timber line tree, is abundant down 

 to 5000 feet in Glacier Park, and scattering individuals may be 

 found occasionally in the valley of the Clark's Pork and its trib- 

 utaries at 3500 feet or less. The only tree of this region which 

 is confined to the highest elevations is Lyall's larch (L. Lyallii) 

 but this species is found only in a part of the Bitter Root Range 

 and along the highest summits of the main divide. The black 



