AGRICULTURAL BOTANY 



137 



drought, to live for a long time on the buds and bark of 

 trees. 



When the cambium layer of an actively growing stem 

 is held in contact with the same layer in another growing 

 stem of the same kind or of a closely similar kind, the 

 two may grow together at the point of contact. It is 

 this fact that makes grafting possible. (See page 159.) 

 The stems of endogens, or inside growers, have prom- 

 inent nodes and are hollow, as in the grasses and the 

 bamboo ; or the center of the stem is filled with pith, as 

 in the corn stalk. The pith is traversed with fibers 

 which are bundles of tubes with other vessels and fibers. 



Leaves. --The leaves of any given species of plant 

 grow from the nodes of the stem in a well-defined ar- 

 rangement which rarely varies in that species. They 



Alternate Opposite Whorled 



FIG. 62. Arrangement of Leaves. 



may have an opposite arrangement, that is, with two 

 leaves, one on each side of the node, or they may have an 

 alternate arrangement, that is, one leaf at a node. 

 Occasionally there are more than two leaves at a node 

 with the space around the stem divided equally among 

 them. This is known as the whorled arrangement. 



