CHAPTER IX 



STEMS 

 Characteristic Features and Types of Stems 



The stem, usually consisting of trunk and branches, is the fun- 

 damental part of the shoot. Upon the stem the other structures 

 of the shoot, such as leaves, flowers, and fruit, depend for their 

 support in the air and sunlight the position most favorable for 

 leaf-activity, pollination, and scattering of seed and fruit. 



Roots, stems, and leaves are intimately related in their activi- 

 ties, and the efficiency of one affects the efficiency of the others. 

 The productivity of most of the cultivated plants depends not 

 only upon a good root system, but also upon a good stem system. 

 In some plants, such as Beets, Turnips, Radishes, Lettuce, and a 

 few others which have very short stems during much of their life, 

 not so much importance is attached to the stem, but even these 

 plants, in order to complete their life cycle, must eventually 

 develop stems upon which to bear flowers and seeds. Among 

 such plants as the trees and grains, the stem is very important. 

 The value of a tree for shade, lumber, or fruit depends largely 

 upon the character of the stem. Likewise, a Corn or Wheat plant 

 with a well developed stem is able to produce larger ears or a 

 better head than a plant with a stem poorly developed. 



In comparing stems with roots the following things may be 

 stated. First, stems bear leaves and flowers, while roots do not. 

 Second, stems are divided into nodes and internodes but roots are 

 not. Third, stems branch at the nodes, while in roots branches 

 arise anywhere. Fourth, in stems pith is nearly always present, 

 while in roots it is usually absent. 



The nodes are the narrow zones, often more or less swollen, at 

 which the leaves and buds as well as the branches arise. The 

 internodes are the zones between the nodes. The division of the 

 stem into nodes and internodes is quite noticeable in the stems of 

 Corn and other Grasses, where the nodes divide the stem into 

 distinct segments. By the elongation of the internodes, the 



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