STRUCTURE AND REQUIREMENTS OF TREES 107 



the tree. It is for this reason that a tree may be hollow, 

 without heart and sap-wood, and still produce foliage 

 and fruit. 



The crown: The crown varies in form in different 

 species pnd is developed by the growth of new shoots from 



bark 



cambium 



sap-wood 



hrart-wocd 



pith 



Fig. 86. — The Cross-Section of a Tree. 



buds. The bud grows out to a certain length and forms 

 the branch. Afterwards it thickens only and does not 

 increase in length. New branches will then form from 

 other buds on the same branch. This explains in part the 

 characteristic branching of trees, Fig. 87. 



The leaves are the stomach and lungs of the tree. 



