STRUCTURE AND REQUIREMENTS OF TREES 109 



used, by the cambium layer in building up the body of 

 the tree. A green pigment, chlorophyll, in the leaf is the 

 medium by which, with the aid of sunlight, the sugars 

 are manufactured. 



FIG. 88. Roots of a Hemlock Tree in their Search for Water. 



The chlorophyll gives the leaf its green color, and this 

 explains why a tree pales when it is in a dying condition 

 or when its life processes are interfered with. The other 

 colors of the leaf the reds, browns and yellows of the 

 fall or spring are due to other pigments. These are 



