of 



enriches the very land it is using. Trash on a 

 forest floor absorbs nitrogenous matter from 

 the air ; every fallen leaf is a flake of a fertilizer ; 

 roots pry rocks apart, and this sets up chemical 

 action. Acids given off by tree-roots dissolve 

 even the rocks, and turn these to soil. A tree, 

 unlike most plants, creates more soil than it con- 

 sumes. In a forest the soil is steadily growing 

 richer and deeper. 



Birds are one of the resources of the country. 

 They are the protectors, the winged watchmen, 

 of the products which man needs. Birds are 

 hearty eaters, and the food which they devour 

 consists mostly of noxious weed-seed and inju- 

 rious insects. Several species of birds feed freely 

 upon caterpillars, moths, wood-lice, wood-bor- 

 ers, and other deadly tree-enemies. Most spe- 

 cies of birds need the forest for shelter, a 

 home, and a breeding-place; and, having the 

 forest, they multiply and fly out into the fields 

 and orchards, and wage a more persistent war- 

 fare even than the farmer upon the insistent 

 and innumerable crop-injuring weeds, and also 

 the swarms of insatiable crop-devouring insects. 



132 



