THE GTMNOSPERM TREES 267 



five feet in height, it may reach twice that in the favorable en- 

 vironment of our southeastern mountains. Hemlock is almost 

 always found in association with other tree species, only rarely 

 as pure stands. Young trees are frequently found making up the 

 "understory" of a forest growth, due to the ability of hemlock to 

 grow in suppression, beneath existing forests of other species, for 

 long periods of time. 



Western hemlock is by far the most important, and the 

 largest, of the four hemlocks found in North America. It is com- 

 monly over a hundred and fifty feet in height (maximum 

 recorded height two hundred fifty nine feet, diameter nine feet), 

 and grows in that region where most trees are giants, namely, the 

 Pacific Northwest, where it has recently become one of the four 

 principal timber trees. Five per cent of this country's sawtimber 

 stand is composed by this species which is just now "coming into 

 its own" as a tree of first rank importance in the northwest. Much 

 of the existing western hemlock is contained in dense pure stands, 

 though it occurs as an occasional constituent in mixture with 

 hardwoods and other conifers. Like its associates, the Douglas fir 

 and Sitka spruce, western hemlock makes its best growth on 

 moist, deep soils, accompanied by a high atmospheric moisture 

 content. 



The True Firs 



The true firs {Abies) have leaves much like those of the pre- 

 ceding three genera, but differ in several important respects 

 (fig. 188). They are rounded at the apex, flattened, possess no 

 stalks, and are not borne on projections of the stem. The thin 

 scaled cones stand erect on the branches, where the scales fall 

 off leaving the slender, conical, central shafts standing upright, 

 often over the winter. 



This genus is represented in North America by ten species, 

 two of which are found in the east and the remaining eight 

 scattered through the western forests. Members of this group have 

 largely succeeded spruce as the nation's Christmas tree, since 

 they do not shed their leaves when taken indoors. Their fra- 

 grance, especially true of balsam fir, further enhances their 

 desirability. 



