CHAPTER XL 

 STEMS 



General Characters. Stems normally grow into the light 

 away from the soil and assume an erect position; they 

 are divided into nodes and internodes. From the nodes 

 grow leaves and in the axil of the leaves stems or modified 

 stems. 



Functions. The stem by its growth elevates the plant 

 above the ground; it produces leaves which, because of the 

 presence of chlorophyll, manufacture food from carbon 

 dioxide and water; it conducts water upward to the leaves; 

 it bears flowers which after fertilization develop into fruit 

 and seed. The seed under normal conditions produces a new 

 plant. 



Origin. Stems are formed by the growth of the plumule 

 of the seed. The continued growth of stems is brought about 

 by cell divisions of apical or lateral buds. 



Units of Structure. All stems are divisible into nodes and 

 internodes. From the nodes leaves, stems and flowers 

 develop, Under certain conditions the internodes will give 

 rise to leaves and branches. 



Nature. Stems are simple or branched. By far the greater 

 number of plants, however, have branched stems. If the 

 stem is branched, the branches may be alternate, one at a 

 node, opposite, two at a node, or whorled, more than two at a 

 node. 



