94 THE STEM. 



140. The root gives birth to no other organs, but itself directly 

 performs those functions which pertain to the relations of the veg- 

 etable with the soil ; its branches bind the plant to the earth ; its 

 newly formed extremities, or fresh rootlets, with the capillary fibrils 

 they bear, imbibe nourishment from it. But the aerial functions 

 of vegetation are chiefly carried on, not so much by the stem it- 

 self as by a distinct set of organs which it bears, namely, the 

 leaves. Hence, the production of leaves is one of the characteris- 

 tics of the stem. These are produced only at certain definite 

 and symmetrically arranged points, called 



141. Nodes, literally knots, so named because the tissues are here 

 condensed, interlaced, or interrupted, more or less, as is conspicu- 

 ously seen in the Bamboo, in a stalk of Indian Corn, or of any 

 other Grass. Here each node forms a complete indurated ring, 

 because the leaf arises from the whole circumference of the stem 

 at that place. When the base of the leaf or leaf-stalk occupies 

 only a part of the circumference, the nodes are not so distinctly 

 marked, except by the leaves they bear, or by the scars left by 

 their fall (Fig. 127, 130). When distinct they are often called 

 joints, and sometimes, indeed, the stem is actually jointed, or artic- 

 ulated, at these points ; but commonly there is no tendency to 

 separate there. Each node bears either a single leaf, or two 

 placed on opposite sides of the stem (Fig. 104), or three or more, 

 placed in a ring (in botanical language, a whorl or verticil) around 

 the stem. The naked portions or spaces that intervene between 

 the nodes are termed 



142. Illternodes, The undeveloped stem is, in fact, made up of 

 a certain number of these leaf-bearing points, separated by short 

 intervals ; and its growth consists, primarily, in the elongation of 

 these internodes (much after the mode in which the joints of a 

 pocket-telescope are drawn out one after the other), so as to sep- 

 arate the nodes to a greater or less distance from each other, and 

 allow the leaves to expand. 



143. This brings to view the leading peculiarity of the stem, 

 namely, that it is formed of a succession of similar parts, developed 

 one upon the summit of another, each with its own independent 

 growth : each developing internode, moreover, lengthens through- 

 out its whole body, unlike the root, which elongates continuously 

 from its extremity alone. The nodes or the leaves they bear are 

 first formed, in close contiguity with the preceding ; then the 



