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BOTANICAL GAZETTE 



competition with the hemlock, and is confined therefore to areas 

 where the latter cannot flourish on account of dryness. Possibly, 

 also, the lodgepole pine has not been able as yet to cross the central 

 mass of the Selkirks, nor to make its way from burn to burn around 

 the bend. It certainly would have little chance to invade the 

 climax forest. 



Populus iremuloides is another prominent member of the burn 

 vegetation, universally distributed, growing in company either with 

 the lodgepole or the hemlock, as the case may be. 



Abies lasiocarpa occurs sparingly in the montane forest. It 

 is rarely to be seen near the river, but is one of the 3 or 4 species 

 forming the tree clusters on exposed ridges. 



The birches, maples, buckthorns, and hazels are found only 

 along the river and the lower waters of its tributaries, and are 

 usually not abundant. 



In the moist river-level forests, especially along the western 

 arm of the river, and in such moist pockets as that found at the foot 

 of Mount Cheops at Rogers Pass, certain shrubs grow in remark- 

 able luxuriance. Among these the most conspicuous are: in the 

 river-level forests, Echinopanax horridum, Taxus brevifolia, Corylus 

 rostrata; in the moist pockets, Vaccinium ovalifolium, Rhododendron 

 albiflorum, alders, and willows. In the moist, well shaded river- 

 level forests, especially along the Columbia between Bigmouth 

 and the great angle made by the Columbia, vegetation reaches 

 a marvelous degree of luxuriance. Here careful measurement 

 indicated that the following spermatophytes and pteridophytes 

 reached a height of 2.50-3 m.: Veratrum viride, Echinopanax 

 horridum, Vagnera amplexijolia, Pteridium aquilinum, Aspidium 

 spinulosum dilatatum. Here also the mosses Hylocomium pro- 

 liferum and species of Thuidium covered the rocks and fallen tree 

 trunks with thick cushions of exquisite foliage. 



The alpine meadow formation.— As previously stated, the 

 alpine meadow and the forest formations interlock, the former fre- 

 quently extending far down below the timber belt in the depres- 

 sions, while the latter reaches upward on the exposed mountain 

 flanks and ridges. The bulk of the alpine meadow vegetation lies 

 between 1800 and 2500 m. The plant associations vary greatly, 



