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places the stripped areas are covered with a second growth of 
small trees but in other places they remain bare and unprotected. 
Among the deciduous trees and shrubs the aspen, mountain- 
alder, mountain-maple and willows are the most common. In 
places the aspen occurs in great numbers and attains considerable 
size and extends as high as timber-line. It, however, decreases 
in size as we ascend the canyon, and when we reach the timber- 
line it is no longer a tree but a low shrub and the leaves are so 
Fic. 41. Ruins of one of the many sawmills which have been operated in the 
canyon, 
much reduced in size that we would scarcely recognize it as the 
same plant occurring at lower altitudes. e mountainsides 
were often covered with patches of aspen trees. Although our 
visit to the canyon was early in September, the temperature 
often dropped to the freezing point toward morning and the 
leaves of the aspen had already assumed the golden and scarlet 
colors characteristic of the autumn, and these bright colors in 
