THE EARTH'S BOUNTY 



liberates and holds in solution the several min- 

 eral compounds of the soil which constitute 

 plant food. The fibrous residue of stems and 

 veins accumulates, gradually disintegrates, and 

 eventually becomes rich loam. 



After ground cover, general tree growth and 

 the idiosyncracies of different species should 

 be understood. The majority of trees can be 

 divided into two classes: tolerant and intoler- 

 ant; which means that some species can en- 

 dure heavy shade until past sapling age, 

 whilst others must have full light from sap- 

 ling age. (Seedlings of both classes are bene- 

 fited by partial shade.) According to the 

 classification made by the Forest Service, 

 young trees are seedlings until three feet 

 high; small saplings until ten feet high; from 

 then until they reach four inches in diameter 

 at about four feet from the ground, large 

 saplings. 



It is generally safe to class the trees which 

 make dense top-growth under the heading of 

 tolerant, and those with light top-growth, 



303 



