46 



A PRIMER OF FORESTRY. 



water enough for all the trees, and often more than 

 enough, as for example in the Adirondack forest. The 

 struggle for space and light is thus more important 

 than the struggle for water, and as it takes place above 

 ground it is also much more easily observed and stud- 

 ied. (See fig. 42 and PI. XXY.) 



Light and space are of such importance because, as 



we have seen, the leaves 

 can not assimilate or di- 

 gest food except in the 

 presence of light and air. 

 The rate at which a tree 

 can grow and make new 

 wood is decided chiefly by 

 its ability to assimilate 

 and digest plant food. 

 This power depends upon 

 the number, size, and 

 health of the leaves, and 

 these in turn upon the 

 amount of space and light 

 which the tree can secure. 



THE LIFE OF A FOREST 

 CROP. 



FIG. 42. On the edge of a very dense 

 forest. The leaning trees are dead, 

 killed by the crowding and shade of 

 their stronger neighbors. Spruce in 

 the White Mountains, New Hamp- 

 shire. 



The story of the life of 



a forest crop is then largely an account of the com- 

 petition of the trees for light and room, and, although 

 the very strength which enables them to carry on 

 the fight is a result of their association, still the 

 deadly struggle, in which the victims are many times 

 more in number than those which survive, is apt 

 alone to absorb the attention. Yet the mutual help 

 of the trees to each other is always going quietly on. 



