REQUIREMENTS FOR HEAT AND MOISTURE. 27 



effects. A dry country, or a dry slope, is apt to be hot as 

 well, while a cool northern slope is almost always moister 

 than one turned toward the south. Still the results 

 of the demand of trees for water can usually be distin- 



Fig. 24.— The Black Hemlock in its home. Cascade Mountains of Washington. 



guished from the results of their need of warmth, and 

 it is found that moisture has almost as great an influ- 

 ence on the distribution of trees over the earth as heat 

 itself. Indeed, within any given region it is apt to be 



