CHAPTER III 



i 



STEMS 



21. Relation to other organs. The stem is connected 

 with the roots and bears the leaves. So constant a feature 

 of the stem is leaf-bearing that the presence of leaves is one 

 method of distinguishing underground stems from roots. 

 Not merely do stems bear leaves, but they usually bear 

 them in such a way as to expose them well to the air and 

 the sunlight. Often stems branch, and in this way in- 

 crease their power of producing and displaying leaves. It 

 is evident that the stem, more than anything else, is the 

 leaf -bearing organ; and in bearing leaves it must be also 

 the channel of communication between them and the roots. 



So closely associated are stems and leaves that they are 

 spoken of together as the shoot; and thus the whole body of 

 the plant of ordinary experience is said to consist of shoot 

 and root, the former usually exposed to the air (aerial), 

 the latter usually exposed to the soil (subterranean). As 

 any branch is merely a repetition of the stem from which it 

 arises, so any branch with its leaves is a shoot, just as the 

 whole stem system with its leaves is a shoot. 



22. External structure. The ordinary stem is a jointed 

 structure. While this is very evident in such stems as the 

 corn-stalk and the cane (seen in fishing-rods), it is often 

 made apparent only by the leaves, which appear at the 

 joints or nodes ( 8). The portions of the stem between the 

 nodes portions which do not bear leaves are the internodes; 

 hence a stem is a series of alternating nodes and internodes. 



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