Vietnam or Thailand ? Vote for the TOP Country of the Week !
Updated: June 20, 2025
By this means they ascend to a considerably greater height, with the same length of stem, than would otherwise have been possible; and they do this with safety, as they secure themselves at intervals by their clasping petioles or tendrils. We have seen that tendrils consist of various organs in a modified state, namely, leaves, flower-peduncles, branches, and perhaps stipules.
Besides the plants already described, Bignonia unguis and its close allies, though aided by tendrils, have clasping petioles. We now come to a small section of plants which climb by means of the produced midribs or tips of their leaves. LILIACEAE. Gloriosa Plantii.
It may be said that the trunks of the ferns, which, like the monocotyledons, are enlarged by the remains of the petioles, decay from the circumference to the centre; and that, deprived of the cortical organs through which the elaborated juices descend to the roots, they are burnt more easily by the action of the oxygen of the atmosphere.
Whilst the plant is young, each leaf consists of three divided leaflets, which barely have distinct petioles, and these are not sensitive; but when the plant is well grown, the petioles of the two lateral and terminal leaflets are of considerable length, and become sensitive so as to be capable of clasping an object in any direction.
We thus see that the sensitiveness of tendrils is a special and localized capacity. It is quite independent of the power of spontaneously revolving; for the curling of the terminal portion from touch does not in the least interrupt the former movement. In Bignonia unguis and its close allies, the petioles of the leaves, as well as the tendrils, are sensitive to a touch.
As all the softer parts had long ago rotted off, we may feel sure, especially in the latter case, that none had been drawn in as food. At this season, therefore, worms drag these petioles into their burrows indifferently by either end, a slight preference being given to the base.
Under some ash-trees growing in a grass- field, 229 petioles were pulled out of worm burrows early in January, and of these 51.5 per cent. had been drawn in by the base, and 48.5 per cent. by the apex.
With leaf- climbers, as we shall soon see, analogous cases frequently occur; but these present no difficulty, as the stem is secured by the clasping petioles. In the many other revolving and twining plants observed by me, I never but twice saw the movement reversed; once, and only for a short space, in Ipomoea jucunda; but frequently with Hibbertia dentata.
The course during 12 hrs., when traced on a bell-glass, apparently represented about four ellipses. The leaves themselves likewise move spontaneously, the main petioles curving themselves in accordance with the movements of the internodes; so that when the latter moved to one side, the petioles moved to the same side, then, becoming straight, reversed their curvature.
The internodes of a variety named "dwarf crimson Nasturtium" did not revolve, but moved in a rather irregular course during the day to the light, and from the light at night. The petioles, when well rubbed, showed no power of curving; nor could I see that they ever clasped any neighbouring object.
Word Of The Day
Others Looking