178. The vine is cither herbaceous or woody. It is a stem too slender and weak to stand erect, but trails along the ground or any convenient support. Sometimes, by means of special organs for this purpose, called tendrils, it ascends trees and other objects to a great height, as the grape, gourd, and other climbing vines.
Vines. 49, Passion-flower (Passiflora lutea) climbing by tendrils. 49, Morning-glory, twining from right to left. 50, Hop, twining from left to right.
179. The twining vine, having also a length greatly disproportioned to its diameter, supports itself on other plants or objects by entwining itself around them, being destitute of tendrils. Thus the hop ascends into the air by foreign aid, and it is a curious fact that the direction of its winding is always the same, viz., with the sun, from left to right; nor can any artificial training induce it to reverse its course. This is a general law among twining stems. Every individual plant of the same species revolves in the same direction, although opposite directions may characterize different species. Thus the morning glory revolves always against the sun
180. The forms of scale-stems are singular, often distorted in consequence of their underground growth and the unequal development of the internodes. They commonly belong to perennial herbs, and the principal forms are described as follows; but intermediate connecting forms are very numerous and often perplexing.
181. The creeper is either subaerial or subterranean. In the former case it is prostrate, running and rooting at every joint, and hardly distinguishable otherwise from leaf-stems, as the twin-flower (Linnaea), the partridge-berry (Mitchella). In the latter case it is more commonly clothed with scales, often branching extensively, rooting at the nodes, axceedingly tenacious of life, extending horizontally in all directions beneath the soil, annually sending up from its terminal buds erect stems into the air. The witch-grass (Triticum repens) is an example. Such plants are a sore evil to the garden. They can have no better cultivation than to be torn and cut to pieces by the spade of the angry gardener, since they are thus multiplied as many times as there are fragments.
Fig. 51. Creeper of "Nimble Will,"or witch-grass; a, Bud; lb, Bases of culms.
182. Utility. Repent stems of this kind are not, however, without their use. They frequently abound in loose, sandy soil, which they serve to bind and secure against the inroads of the water and even the sea itself. Holland is said to owe its very existence to the repent stems of such plants as the mat-grass (Arundo arenaria), Carex arenarius and Elymus arenarius, which overrun the artificial- dykes upon its shores, and by their innumerable roots and creepers apparently bind the loose sand into a firm barrier against the washing of the waves. So the turf, chiefly composed of repent grass-stems, forms the only security of our own sandy or clayey hills against the washing rains.
183. The rhizome or root-stock differs from the creeper only in being shorter and thicker, having its internodes but partially developed. It is a prostrate, fleshy, rooting stem, either wholly or partially subterranean, often scaly with the bases of undeveloped leaves, or marked with the scars of former leaves, and yearly producing new shoot3 and roots. Such is the fleshy, horizontal portion of the blood-root, sweet-flag, water-lily, bramble (the latter hardly different from the creeper).
184. The growth of the rhizome is instructive, marking its peculiar character. Each joint marks the growth of a year. In spring the terminal bud unfolds into leaves and flowers to perish in autumn - a new bud to open the following spring - and a new internode with its roots to abide several years. The number of joints indicates, not the age of the plant, but the destined age of each internode. Thus if there are three joints, wo infer that they are triennial, perishing after the third season, while the plant still grows on.
Fig. 52. Rhizoma of Solomon's-seal (Polygonatum multiflora) a, Fragment of the first year's growth; b, the second year's growth; c, growth of the third year; d, growth of the present (fourth) year, bearing the stem which, on decaying, will leave a scar (seal) like the rest. 53. Pre. morse stem of Trillium.
185. The premorse root-stock, formerly described as a root, is a short, erect rhizome, ending abruptly below as if bitten square off (prasmorsus). This is owing to the death of the earlier and lower in-; ternodes in succession, as in the horizontal rhizome. Scabious, Viola pedata, benjamin-root (Trillium) are examples.
186. Crown of the root designates a short stem with condensed internodes, remaining upon some perennial roots, at or beneath the surface soil after the leaves and annual stems have perished.
187. The tuber is an annual thickened portion of a subterranean stem or branch, provided with latent buds called eyes, from which new plants ensue the succeeding year. 'It is the fact of its origin with the ascending axis, and the production of buds that places the tuber among stems instead of roots. The potato and artichoke are examples.
Tubers as they grow. 54, The common potato (Solatium). 55, Artichoke (Helianthus) 56, Sweet potato (Convolvulus).
188. How toe potato grows. The stem of the potato plant sends out roots from its base, and branches above like other plants; but wo observe that its branches have two distinct modes of development. Those branches which arise into the air, whether issuing from the above-ground or the under-ground portion of the stern, expand regularly into leaves, etc, while those lower branches which continue to grope in the dark, damp ground, cease at length to elongate, swell up at the ends into tubers with developed buds and abundance of nutritious matter in reserve for renewed growth the following year.
189. The corm is an under-ground, solid, fleshy stem, with condensed internodes, never extending, but remaining of a rounded form covered with thin scales. It is distinguished from roots by its leaf-bud which is either borne at the summit, as in the crocus, or at the side, as in the colchicum and putty-root (Aplectrum).
190. How the corm grows. The corm usually accomplishes its part in vegetation in one or two seasons, and then gradually yields up its substance and life for the nourishment of the new progeny formed from the axils of its upper scales in case of the Crocus and Gladiolus, or the single new corm from the axil of a lateral scale, as in Colchicum.
57, Corms of putty-root (A plectrum); a. of last year, b, of the present year. 58, Scale bulb of white lily. 59, Scale bulb of Oxalis violacea.
191. The Bulb partakes largely of the nature of the bud. It consists of a short, dilated axis, bearing an oval mass of thick, fleshy scales closely packed above, a circle of adventitious roots around its base, and a flowering stem from the terminal, or a lateral bud.
192. How multiplied. Bulbs are renewed or multiplied annually at the approach of winter by the development of bulbs from the axils of the scales, which increase at the expense of the old, and ultimately become detached. Bulbs which flower from the terminal bud are necessarily either annual or biennial: those flowering from an axillary bud may be perennial, as the terminal bud may in this case continue to develop new scales indefinitely.
193. Bulbs are said to be tunicated when they consist of concentric layers, each entire and enclosing all within it, as in the onion. But the more common variety is the scaly bulb - consisting of fleshy, concave scales arranged spirally upon the axis, as in the lily.
60. Bulb of Lilium superbum, with habit of a rhizome; a, full-grown bulb sending up a terminal stem c, and two offsets bb, for the bulbs of next year.
61, Corm of Crocus, with new ones forming above; 62, Vertical section of the same; 63, Section of bulb of Hyacinth with terminal seape and axillary bulblet; 64, Section of bulb of Oxalis violacea, with axillary scapes.
194. The tuber, corm and bulb are analogous forms approaching by degrees to the character of the bud, which consists of a little axis bearing a covering of scales. In the tuber the axis is excessively developed while the scales are reduced to mere linear points. In the corm the analogy is far more evident, for the axis is less excessive and the scales more manifest, and lastly in the bulb the analogy is complete, or overdone, the scales often becoming excessive.