﻿4H 



BOTANICAL GAZETTE 



designate three formations in the Selkirks: forest, alpine grassland, 

 and alpine desert. The first two interlock, the latter two grade im- 

 perceptibly into each other. Within the forest are streams with their 

 distinct plant life, and occasional areas of swamp and bog, as well 

 as cliffs and gravel slides which exhibit desert conditions and to some 

 extent the same species as the alpine deserts. Above the forest 

 there is every gradation, from alpine rivulet to barren cliff. To 

 attempt to reduce all this to a classified and logically complete 

 system of subformations, societies, etc., is a task in which the writer 

 can see neither profit nor hope. The interesting facts and relations 

 which may be observed will be brought out simply as facts. 



The forest formation. — The forest covers the entire area 

 up to the timber line at about 1900 m. The most striking feature 

 in its general physiognomy is the increase in luxuriance westward. 

 In the Rockies and southeastern portion of the Selkirks the trees are 

 usually not more than 30-50 cm. in diameter, and 15-25 m. high. 

 In the Columbia Valley from Quartz Creek and the Beaver north- 

 ward, however, and on all the western slopes of the Selkirks, the 

 forests attain a magnificent development. The trees of various 

 species are commonly 100-150 cm. in diameter and 30-60 m. high, 

 suggesting, though by no means equaling, the marvelous forests of 

 the Puget Sound region. It is scarcely to be doubted that this 

 greater development is bound up with a greater precipitation over 

 the area named. Related facts in regard to the peculiar distribu- 

 tion of certain species will be brought out later. 



The forest is further diversified by the effects of fire. Fires 

 have occurred apparently from remote periods, and all phases 

 of succession can be found, culminating in the climax type. The 

 chief cause of the fires seems to be lightning. A tree with a mass 

 of dead resinous branches is a highly inflammable object, and, as a 

 matter of experience, an outlook from a vantage point after a 

 sharp thunderstorm usually reveals one or more slender columns 

 of smoke rising from the forest. Fortunately such fires often die 

 out before much damage is done. 



With respect to altitude, the forest is rather plainly composed 

 of two zones, which, in accordance with a usage now happily 

 becoming somewhat uniform, we may designate as the montane 



