CHAPTER X. 

 THE STEM. 



103. Definition. — The shoot is almost always segmented 

 into members of two kinds, the stem and leaves. The stem 

 is the central axis of any shoot, and the leaves are lateral 

 outgrowths, or branches, of it. These two members cannot 

 be accurately defined, but are in most cases readily recog- 

 nized. Leaves commonly differ from the stem in their 

 flattened form, limited growth," and position, subtending the 

 lateral shoots. (See further p. 96.) 



104. Nodes and internodes. — Upon examining the surface 

 of the stem, it is almost always readily distinguishable into 

 distinct regions, the nodes and internodes. The nodes are 

 the narrow zones, often somewhat swollen (whence the 

 name), at which one or more leaves arise. The internodes 

 are the zones between the nodes. Upon watching the de- 

 velopment of the stem from the terminal bud, it will be 

 seen that new nodes and internodes are constantly emerging 

 from its base, and that the leaves formed at the nodes are 

 successively expanding. This emergence of the internodes 

 is due to their growth. The amount of growth, however, 

 varies greatly in different plants, and even in different parts 

 of the same plant. In many cases the internodes are con- 

 siderably and uniformly elongated; the leaves are then dis- 

 tributed along the stem at considerable and regular intervals. 

 In other cases the internodes remain very short, and the 

 leaves are, therefore, crowded. They may be so crowded as 



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