384 



ELEMENTARY BIOLOGY 



increasing the actual amount of growth, it is plain that the value of the 

 growth can be increased if the trees do not have curved or twisted 

 trunks or branches. By selecting straight-growing varieties and by 

 concentrating the growth in the best trees (by thinning out the least 

 desirable ones) it is possible to increase the yield of a forest area. 





Fig. 20I. United States forest reserves 



The economy of national control of forests, as well as the protection of public interests 

 thereby, has been strikingly demonstrated since our entrj' upon the Great War 



424. Avoiding wood waste. In the national forests the lum- 

 bermen are given a practical demonstration of the value of 

 scientific cutting, seeding, reforesting, etc., and also of the 

 economical handling of growth. Damage to trees often results 

 from careless lumbering. The tree that is being cut down is 

 sometimes damaged, and it is sometimes allowed to injure trees 

 that are left standing. When wood was cheap, a great deal 

 from each tree was left to rot on the ground. Now everything 

 that can possibly be used is saved, and the remaining brush- 

 wood is carefully burned, instead of being left under the trees 

 as a constant fire risk. 



