216 WILLIAM S. COOPER 



Menziesia ferruginea, Cassiope Mertensiana (Bong.) Don, Mon- 

 eses uniflora, Pyrola chlorantha Sw., P. uliginosa, Phyllodoce 

 glanduliflora (Hook.) Coville, P. intermedia (Hook.) Rydb., 

 P. empetrijormis (Smith) D. Don, Cornus canadensis L. Mosses 

 are very abundant, the Uving plants and dead remains forming 

 deep accumulations. 



The difference between the forests of the two zones, partic- 

 ularly in regard to the larger woody species, consists rather in 

 the elimination in the upper of certain species important in the 

 lower, than in complete substitution of species. The absence 

 of Tsuga, Pseudotsnga, Thuja, and Fatsia profoundly changes 

 the aspect and character of the forest. This difference is an 

 essential one too, since Tsuga, Thuja, and Fatsia are distinc- 

 tively Pacific Coast species, while Picea Engelmanni and Ahies 

 lasiocarpa, dominating the Subalpine Zone, belong almost as 

 distinctively to the Rocky Mountain region. In the lower 

 growth conspicuous differences exist. The heaths, of little 

 importance in the Montane Zone, are greatly predominant in 

 the Subalpine; the mosses too are much more abundant in the 

 latter. 



For the study of succession, the Subalpine Zone is far more 

 favorable than the Montane. In the former many of the glaciers 

 reach their lower limits. None extend into the Montane. Since 

 they are now in retreat, we find freshly exposed rock surfaces and 

 moraines, and an abundance of talus slopes and shingle flats 

 as well. In the vicinity of Robson Pass conditions were un- 

 favorable for the study of the Rock Surface Succession, but 

 there were easily available samples of the other three, .in all 

 stages of development. Most of the successional studies were 

 made in the vicinity of Robson Pass and at Lake Kinney. 



C. THE SUCCESSIONS 



1. The Rock Surface Succession 



Rock surfaces, mainly steep cliffs, are naturally common in the 

 Mt. Robson region. Most of them are more or less unstable 

 because of steepness and creviced condition, and are weathering 



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