24 THE SCHOOL BOOK OF FORESTRY 



changes very remarkably from one century to 

 another. For example, in some sections, the red 

 and black oaks are replacing the white oaks. 

 Some trees are light-lovers. They require much 

 more sunlight than others that do well under 

 heavy shade. Oak trees require plenty of light ; 

 maples or beeches thrive on little light. 



The seed of trees requiring little light may 

 be scattered in a dense forest together with that 

 of trees which need plenty of daylight in order 

 to make normal growth. The seedlings that like 

 shade will develop under such conditions while 

 those that need light will pine away and die. 

 Gradually the shade-loving trees will replace the 

 light-loving trees in such a forest stand. Even 

 the different trees of the same family often strive 

 with one another for light and moisture. Each 

 tree differs from every other one in shape and 

 size. Trees will adapt themselves to the light 

 and moisture conditions to which they are ex- 

 posed. A tree that has access to plenty of 

 moisture and sunlight grows evenly from the 

 ground to its top with a bushy, wide-spreading 

 crown. The same tree, if it grows in the shade, 

 will reach a greater height but will have a small 

 compact crown. Trees run a race in their rapid- 



