The student of plant life must always be careful to distinguish between roots and underground stems, for there are many examples of creeping and tuberous stems which resemble certain roots in general appearance. A true root bears no buds, and, therefore, is not capable of producing new plants. If a root creeps under the ground, as does the root of the Barley Grass, it merely serves the purpose of collecting nourishment from a wider area—a matter of considerable importance when the soil is dry and deficient in suitable mineral food. A creeping stem, on the other hand, developes buds as it proceeds, each bud giving rise to a new plant; and the creeping itself is the result of the growth of a permanent terminal bud.
Again, when studying plants for the purpose of identification, it is often important to note whether the root is annual, biennial, or perennial; that is, whether the root lives for one season only, lives throughout the winter, and supports the plant for a second season, or retains its life for an indefinite number of years.
Most of the roots that live over one season are of a fleshy nature, thick and tapering, or tuberous, and contain more or less stored nourishment which assists the new growths that are called forth by the warmth and light of the early spring sun.
The Stem
The stems of plants exhibit a much greater variety of structure and habit than do the roots. Their chief functions are to support the leaves and flowers, and to arrange these parts in such a manner that they obtain the maximum of light and air; also to form a means of communication by which the sap may pass in either direction. Stems also frequently help to protect the plant, either by the development of thorns or prickles, or by producing hairs which prevent snails and slugs from reaching and devouring the leaves and flowers.
The character of the stem is often of some importance in determining the species, so we must now note the principal features that should receive our attention.
As regards surface, the stem may be smooth or hairy. In general form, as seen in transverse section, it may be round, flattened, triangular, square, or traversed longitudinally by ridges and furrows more or less distinct. Flattened stems are sometimes more or less winged with leaf-like extensions, as in the Everlasting Pea, in which case the wings perform the functions of foliage leaves. It should also be noted whether the stems are herbaceous, or woody, and whether they are hollow, or jointed.
In some plants the stem is so short that the leaves appear to start direct from the root, as in the Dandelion and Primrose. Such stems are said to be inconspicuous.
