THE PLANT. 67 



Stems. 



Plants are either annual, biennial or perennial. 



Annual and biennial plants usually have herbaceous stems, 

 while perennial plants generally have woody stems. 



We have herbaceous and woody stems, that grow upright 

 as trees and grasses, and we have vines that twine or climb, and 

 we have plants that trail upon the ground. The purpose of the 

 stem in its different forms is always to bring its foliage into the 

 best position to receive air and sunlight. 



As to growth we distinguish two distinct classes; as for .ex- 

 amples the corn plant and the oak. The corn-stalk has an inside 

 growth and the oak has its growth from the outside. So we call 

 the outside growing stem exogenous ; and the inside growing 

 stem endogenous. 



The stem is the ascending axis as the root is the descending 

 axis. The ascending axis bears buds and leaves. If buds appear 

 on the roots they are adventitious or as the term indicates they 

 appear by chance. 



Stems grow according to the nature of the plant, either 

 erect as the maple trunk, or prostrate as in certain bushes and 

 vines. 



All stems do not grow above ground. Botanists have there- 

 fore described various forms of underground stems, as the tuber 

 (potato), the bulb (onion), the corm (indian turnip), the rhizoma 

 (calamus). 



Stems are subject to various modifications, and they serve 

 various purposes. The study of stems is of interest to the ag- 

 riculturist because of their products. They may bear flowers and 

 fruit; they may be used for food; they may furnish timber for 

 building purposes. We find them used in the material of many 

 manufactured products. 



The uses of stems may be briefly stated as follows : 



1. To serve as a framework and support for limbs, leaves, buds, 

 flowers, and fruit. 



2. To bring the various organs above ground into the best position 

 to receive light and air. 



