FOREST DISTRIBUTION' AND COMPOSITION. 



205 



by bare plains. Along the creeks there grow a variety of hardwoods. 

 It was never a continuous forest as was the Eastern Forest. The open- 

 ness of this forest on the Eockies and on the eastern slopes of the 

 Sierra Nevadas is in marked contrast to the western slopes of the 

 Sierras, where there are to be seen the densest and most remarkable 

 woods of the world, Fig. 51. This is due to the peculiar distribution 

 of the rainfall of the region. The precipitation of the moisture upon 

 the northwest coast where the trees are dripping with fog a large 



Fig", so. Open Western Forest, Bull Pine. Flag-staff, A rizona. 

 U. S. Forest Service, ,' 



part of the time, is unequaled by that of any other locality on the 

 continent. But the interior of this region, which is shut off by the 

 high Sierra Nevadas from the western winds, has a very light and 

 irregular rainfall. Where the rainfall is heavy, the forests are dense; 

 and where the rainfall is light, the trees are sparse. 



Along the Eockies the characteristic trees are Engelmann's spruce, 

 bull ]iine, Douglas fir, and lodgepole pine. As one goes west, the 

 variety of trees increases and becomes, so far as conifers are concerned, 

 far greater than in the east. Of 109 conifers in the United States, 



