STRUCTURE AND REQUIREMENTS OF TREES 109 



used by the caml^ium 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. 





t:i22^ 



.:«»*MiS3;sc<.. -^ I 



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 



