OUR FORESTS 



109 



becomes like a sponge, holding water through long periods of 

 drought. The roots of the trees, too, help hold the soil in place. 

 The gradual evaporation of water through the stomata of the leaves 

 cools the atmosphere, and this tends to precipitate the moisture 

 in the air. Eventually the dead bodies of the trees themselves are 

 added to the organic covering, and new trees take their place. 



Other Uses of the Forest. In some localities forests are used 

 as windbreaks and to protect mountain towns against avalanches. 



FOREST REGIONS \ /S^ ml Forest regions 



I Heaviest forests 



The forest regions of the United States. 



In winter they moderate the cold, ard in summer reduce the heat 

 and lessen the danger from storms. Birds nesting in the woods 

 protect many valuable plants which otherwise might be destroyed 

 by insects. 



Forests have great commercial importance. Pyrogallic and 

 other acids are obtained from trees, as are tar, creosote, resin, tur 

 pentine, and many useful oils. The making of maple sirup and 

 sugar forms a profitable industry in several states. 



The Forest Regions of the United States. The combined area 

 of all the forests in the United States, exclusive of Alaska, is about 

 500,000,000 acres. This seemingly immense area is rapidly de- 



