INTRODUCTORY CHAPTER. 



descend, and tliey together constitute the vegetable axis. In its early stage this 

 axis is simple, but by successive growths it -Qsually gives off branches, which form 

 secoiulnnj axes; each branch may. thus be regarded as an independent axis. 



The point of junction of the stem and root is the neclc {collum, c). It is from 

 this point, which may be thickened, shortened, or obscure, that the ascending 

 fibres of the stem and the descending fibres of the root diverge. 



The stem, which alone possesses the power of emitting lateral expansions, 

 develops from its sides more or less flattened bodies, the leaves (p). The point 

 at which the leaves issue from the stem is generally thickened, and is termed a 

 node (nodus) ; the intervals between the nodes ai'e termed internodes (internodium, 

 merithallus). When the nodes develop leaves only, the stem remains perfectly 

 simple or unhranched ; but at each node a hud {gemran, b, b) may spring from the axil 

 of the leaf; and this bud, which appears at first as a small protuberance, afterwards 

 becomes a hranch [ramus), which lengthens, develops leaves, and ramifies in its turn. 

 The buds springing from the axils of the leaves on the primitive axis thus give 

 origin to as many fresh axes, whence it results that the mother- plant is repeated 

 by every bud which it produces. Hence it is more logical to say that a plant 

 multiplies, than that it divides by branching ; and a vegetable may thus be looked 

 upon, not as an individual, but as a collective being, or an aggregation of individuals 

 nourished in common, like the zoophytes of a coral. 



The node does not always produce a leaf and bud; the bud may be absent or 

 scarcely visible, or the leaf may be imperfectly developed : but the latter is rarely 

 entirely suppressed; and when the bud is undeveloped, it is owing to the rigour 

 of the climate or the short duration of the plant. 



Leaves are not developed promiscuously on the stem ; they may be given off 

 singly, when they are alternate (alterna, fig. 2) ; or two may be placed opposite to 

 each other (opposita, fig. 3) ; or they may be whorled around the stem [verticilJata, 



2. Toad-flax, Alternate leaves. 



3. St. .Tohn-s Wort. 

 Oppoblte loaves. 



4, Madder. Whorled leayes. 



fig. 4). Stem-leaves are rarely whorled, but floral leaves are arranged in several 

 superimposed whorls {verticilli)- 



Alteniate leaves, though apparently scattered without order on the axis, are 

 really arranged in a spiral (fig. 6) ; so that, in starting from any one leaf (1), 

 we arrive, after one or more turns of the spiral, at another leaf (6), placed 



