THE TREE 13 



surface to the action of the sun and air. Unlike the roots 

 the branches have a more or less regular arrangement. 



Each species of tree has its characteristic form of crown 

 and habit of branching. In the open the kind of tree can often 

 be told from the distance by the form of crown, as elm by its 

 vase shaped crown, maple by its oval crown, spruce by its 

 conical crown. The form of crown produced by a tree in the 

 woods differs from the form of crown produced by the same 

 kind of tree grown in the open. This is due to crowding by 

 neighboring trees, which restricts lateral development. The 

 form of crown developed under forest conditions is as charac- 

 teristic of the species as the form in the open. The form of the 

 crown varies also with the age of the tree. Trees in early life 

 have a more or less conically shaped crown due to rapid height 

 growth. In old age the crown widens out and forms a flat or 

 rounded top. There is an intimate relation between the size 

 of the crown and the extent of the root system. If for any rea- 

 son the one is not allowed its full development it will have a 

 corresponding effect on the other portion. This does not mean 

 that there is a definite connection between a particular root and 

 a certain branch. It is not true that when a root is cut off a 

 branch fed by that root dies. Neither is it true that the roots 

 on one side of a tree feed only the corresponding side of the 

 crown, and that by fertilizing the ground on one side of a tree 

 the crown can be made to extend in that direction. All the 

 roots of a tree help to obtain water and salts from the soil for 

 the use of the entire tree. 



The leaves may be said to be the lungs and stomach of the 

 tree. In them are carried on respiration, transpiration, absorp- 

 tion of food from the air and the manufacture of food mate- 

 rials. The shape and size of leaves vary in different trees, 

 each kind of tree having a different form. They vary from the 

 broad, flat leaves of hardwoods to the long, needlelike leaves 

 of conifers or evergreen trees. Even on the same tree there 

 is considerable variation in the shape and size of leaves. 



