Читать книгу Field and Woodland Plants - William S. Furneaux - Страница 7

Table of Contents

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.

Running Underground Stem of Solomon's Seal

a, Terminal bud from which the next year's stem is developed; b, Stem of the present year; c, and d, Scars of the stems of previous years.

The longer and conspicuous stems are either simple or branched, and they may be erect, prostrate, trailing, climbing, or running. In the case of climbing stems it should be noted whether the necessary support is obtained by means of tendrils, rootlets, or suckers, or by the twining of the stem itself.

Running stems are those which run along the surface of the ground by the continued growth of a terminal bud, and produce new plants at intervals, as in the case of the Wild Strawberry. Many stems, however, creep under the ground, and these should always be distinguished from running roots, from which they may be known by the production of buds that develop into new plants, as in the Iris and Solomon's Seal.