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In the nine vigorous plants observed by me, it is certain that neither the slight spontaneous movements nor the slight sensitiveness of the flower-peduncles aided the plants in climbing.
The young internodes of the Lophospermum as well as the petioles are sensitive to a touch, and by their combined movement seize an object. The flower-peduncles of the Maurandia semperflorens revolve spontaneously and are sensitive to a touch, yet are not used for climbing.
Again, the tendrils of some few plants never contract spirally unless they have first seized hold of some object; if they catch nothing they hang down, remaining straight, until they wither and drop off: this is the case with the tendrils of Bignonia, which consist of modified leaves, and with those of three genera of the Vitaceae, which are modified flower-peduncles.
When I made this prediction, I knew of only one imperfect case, namely, of the young flower-peduncles of a Maurandia which revolved slightly and irregularly, like the stems of twining plants, but without making any use of this habit.
CUCURBITACEAE. Homologous nature of the tendrils Echinocystis lobata, remarkable movements of the tendrils to avoid seizing the terminal shoot Tendrils not excited by contact with another tendril or by drops of water Undulatory movement of the extremity of the tendril Hanburya, adherent discs VITACAE Gradation between the flower-peduncles and tendrils of the vine Tendrils of the Virginian Creeper turn from the light, and, after contact, develop adhesive discs SAPINDACEAE PASSIFLORACEAE Passiflora gracilis Rapid revolving movement and sensitiveness of the tendrils Not sensitive to the contact of other tendrils or of drops of water Spiral contraction of tendrils Summary on the nature and action of tendrils.
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.
The present species is unique in one respect. This remark, and the fact of the flower-peduncles being decidedly flexuous, led me carefully to examine them. They never act as true tendrils; I repeatedly placed thin sticks in contact with young and old peduncles, and I allowed nine vigorous plants to grow through an entangled mass of branches; but in no one instance did they bend round any object.
The flower-peduncles, which stand up above the end of the shoot, are carried round and round by the revolving movement of the internodes; and when the stem is securely tied, the long and thin flower- peduncles themselves are seen to be in continued and sometimes rapid movement from side to side. They sweep a wide space, but only occasionally revolve in a regular elliptical course.
The whole tendril had five disc-bearing branches of equal thickness and apparently of equal strength; so that after having been exposed during ten years to the weather, it would probably have resisted a strain of ten pounds! SAPINDACEAE. Cardiospermum halicacabum. In this family, as in the last, the tendrils are modified flower-peduncles.
The most different organs stems, branches, flower-peduncles, petioles, mid-ribs of the leaf and leaflets, and apparently aerial roots all possess this power. The first action of a tendril is to place itself in a proper position.
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