110 STUDIES OF TREES 



angular crystals of different hues, which at certain times 

 of the year become more conspicuous than at others, a 

 phenomenon which explains the variation in the colors 

 of the leaves during the different seasons. 



It is evident that a tree is greatly dependent upon its 

 leaves for the manufacture of food and one can, therefore, 

 readily see why it is important to prevent destruction of 

 the leaves by insects or through over-trimming. 



The root: The root develops in much the same manner 

 as the crown. Its depth and spread will vary with the 

 species but will also depend somewhat upon the condition 

 of the soil around it. A deep or a dry soil will tend to 

 develop a deep root, while a shallow or moist soil will 

 produce a shallow root, Fig. 88. 



The numerous fine hairs which cover the roots serve 

 the purpose of taking up food and water from the soil, 

 while the heavy roots help to support the tree. The root- 

 hairs are extremely tender, are easily dried out when 

 exposed to the sun and wind, and are apt to become over- 

 heated when permitted to remain tightly packed for any 

 length of time. These considerations are of practical im- 

 portance in the planting of trees and in the application 

 of fertilizers. It is these fine rootlets far away from the 

 trunk of the tree that have to be fed, and all fertilizers 

 must, therefore, be applied at points some distance from 

 the trunk and not close to it, where merely the large, 

 supporting roots are located. In the cultivation of trees 

 the same principle holds true. 



Requirements of trees: Trees are dependent upon 

 certain soil and atmospheric conditions which influence 

 their growth and development. 



(1) Influence of moisture: The form of the tree and 

 its growth and structure depend greatly upon the supply 



