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However this may be, the fact is certain that a tendril which has caught a round stick with its extreme point, can work itself onwards until it has passed twice or even thrice round the stick, and has permanently grasped it. Hanburya Mexicana.
A nice case of co-adaptation here comes into play: in all the other tendrils observed by me, the several branches become sensitive at the same period: had this been the case with the Hanburya, the inwardly directed, spur-like branch, from being pressed, during the revolving movement, against the projecting end of the shoot, would infallibly have seized it in a useless or injurious manner.
We have seen that such discs are formed by two species of Bignonia, by Ampelopsis, and, according to Naudin, by the Cucurbitaceous genus Peponopsis adhaerens. In Anguria the lower surface of the tendril, after it has wound round a stick, forms a coarsely cellular layer, which closely fits the wood, but is not adherent; whilst in Hanburya a similar layer is adherent.
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.
Whether the internodes likewise revolve I did not observe. In Anguria Warscewiczii, the internodes, though thick and stiff, revolve: in this plant the lower surface of the tendril, some time after clasping a stick, produces a coarsely cellular layer or cushion, which adapts itself closely to the wood, like that formed by the tendril of the Hanburya; but it is not in the least adhesive.
This layer is analogous to the adhesive discs formed by the extremities of the tendrils of some species of Bignonia and of Ampelopsis; but in the Hanburya the layer is developed along the terminal inner surface, sometimes for a length of 1.75 inches, and not at the extreme tip.
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