CHAPTER III. 



THE STEM. 



1. Besides the distinction of stems based on their duration 

 — as annual, biennial and perennial — they may also be desig- 

 nated as herbaceous and woody. Illustrations of woody 

 stems are seen in all shrubs and trees. Herbaceous stems 

 are composed of soft or succulent tissue. They are usually 

 green and contain no wood except in the slender and often in- 

 distinctly distinguishable woody strands. A few stems and 

 branches have special names, as culm, which is the jointed, 

 often hollow stem of the Grass and Sedge families ; stolons 

 and runners, which are slender, trailing, rooting branches; 

 tendrils, which are slender, elongated, twining branches; 

 spines and thorns, which are the hardened, pointed, some- 

 times merely stunted branches. 



Collect illustrative specimens of the various kinds of stems for examina- 

 tion in the class-room. Draw outline figures of each kind. In case of the 

 woody stems, the leaf-scars should receive attention. Make an outline figure 

 giving the exact shape, which will be uniform for each species of plant. 

 Note the dots regularly distributed in the scar. These are the ends of the 

 severed woody strands that passed from stem to leaf. Note the numerous but 

 somewhat indistinct scars, very close together, situated at a considerable dis- 

 tance from the end of the twig. The portion beyond this point is the growth 

 of the last season. The scars indicate the position of the bud-scales of the 

 terminal bud of that season. 



2. Underground stems sometimes resemble roots, but they 

 are distinguished by having nodes (joints) and scales. The 

 latter represent leaves, above which, or in whose axils, buds 

 may be detected. They are also terminated by a bud. Rhi- 

 zome is the name applied to the elongated slender form, and 

 tuber to the short and much thickened stem. The under- 



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