CHAPTER XXVIII 



STEMS 



Functions. The main divisions of a plant are the 

 root, stem, and leaves. The materials from which the 

 plant makes its own food are taken in through the 

 roots and through the leaves. Since the leaves are the 

 factories in which the food is manufactured, the raw 

 materials, water and solutes, which are taken in 

 through the roots, must be transferred to them. In 

 return, some of the food, after it has been made, must 

 be carried to the roots. This necessitates a transfer 

 of materials both to and from the leaves. To make 

 starch, we already know, the leaf must have light. 

 Clearly, it would be a decided disadvantage to plants 

 if all of their leaves were attached directly to the roots. 

 In most plants an intermediate part, the stem, is present. 

 This connects the roots with the leaves and thus forms 

 a passageway for the movement of food and raw 

 materials. The chief function of stems, however, is to 

 bring the leaves up into the sunlight where they can 

 work to best advantage. 



Kinds. Stems determine to a great extent the gen- 

 eral form of plants. They often branch, and in that 

 way increase their power for displaying the leaves to 



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