HABIT. 11 



zone. Other trees in this zone are Tamarack, Engelmann Spruce, 

 Lodgepole Pine, and Cedar. Throughout the range of the Western 

 Hemlock broadleaf trees are so few that they are of no consequence as 

 factors in the mixture. Where the climate is too dry to be generally 

 favorable, Hemlock takes refuge on north slopes and in shaded valleys, 

 where it can hold its own against Fir mainly because, since fire is 

 infrequent, the latter finds an unsuitable seed bed and insufficient light 

 in such localities. 



A list of the trees of Oregon and Washington contains a few which 

 seldom or never occur in mixture with Hemlock, but it is given for 

 reference on page 54. 



UNDERGROWTH. 



Since Hemlock rarely forms a pure stand it has no characteristic 

 undergrowth of its own. Vine Maple is common and Oregon Grape, 

 ferns, and mosses constitute the smaller growth. In low, wet situa- 

 tions Devil's Club and Salmonberry are often abundant. No shrub is 

 more characteristic of the pure fir forest than Salal, which prefers a 

 dry soil and is therefore not much in evidence in the moist localities 

 where Hemlock is at its best. Where it occurs forest reproduction is 

 poor, for Salal covers the ground with a dense thicket 2 or 3 feet high. 

 The leaves are thick and oily and encourage rather than prevent fire. 

 A list of some of the more important shrubs which occur in the forests 

 of Washington and Oregon, will be found on page 55. 



HABIT. 



The Western Hemlock has been found with a diameter of S and a 

 height of 250 feet, and these dimensions may occasionally be surpassed. 

 As a rule mature trees are from 3 to 5 feet in diameter at breastheight. 

 The trunk is exceedingly cylindrical, although often with a sudden, 

 irregular buttressing near the base, due to the germination of the 

 seed on a log or stump. The branches are small and pendulous, form- 

 ing a narrow spire-shaped crown which otters little resistance to the 

 wind and serves somewhat to offset the insecurity of a shallow root 

 system. Near the top of the tree and where exposed to the light the 

 foliage is exceedingly dense and tufted, appearing almost fascicled, a 

 provision which secures a very large leaf surface. Overtopped trees 

 are able to form spreading crowns, and thus to accomplish the same 

 result. The Hemlock clears itself of branches somewhat slowly. 



TOLERANCE. 



Western Hemlock will germinate and grow under dense shade. 

 This characteristic, called tolerance, is one of the most important 

 factors in determining the composition of the forest. Red Fir requires 

 abundant light in youth, and hence seedlings of this species do not 



