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The rate of revolution varies from one to five hours in different species, and consequently is in some cases more rapid than with any twining plant, and is never so slow as with those many twiners which take more than five hours for each revolution. The direction is variable even in the same individual plant. In Passiflora, the internodes of only one species have the power of revolving.
It is stated by that observer, "that a thread weighing no more than the thirty-second of a grain, if placed on the tendril of the Passiflora gracilis, will cause it to bend; and merely to touch the tendril with a twig causes it to bend; but if the twig is at once removed, the tendril soon straightens itself.
In a letter to me, in 1839, Mr. Herbert told me that he had then tried the experiment during five years, and he continued to try it during several subsequent years, and always with the same result. This result has, also, been confirmed by other observers in the case of Hippeastrum with its sub-genera, and in the case of some other genera, as Lobelia, Passiflora and Verbascum.
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.
When a tendril has caught a yielding object, this is sometimes enveloped and still further secured by the spiral folds, as I have seen with Passiflora quadrangularis; but this action is of little importance. A far more important service rendered by the spiral contraction of the tendrils is that they are thus made highly elastic.
Sometimes we climbed up a solid road, blasted out of the face of the black cliffs, or crept along the shore of the tranquil lagoon, frightening the land-crabs into their holes as they felt the shake of the approaching carriage. Palms and passiflora abounded, the latter being specially magnificent.
It makes no difference what sort of object a tendril touches, with the remarkable exception of other tendrils and drops of water, as was observed with the extremely sensitive-tendrils of Passiflora gracilis and of the Echinocystis. I have, however, seen tendrils of the Bryony which had temporarily caught other tendrils, and often in the case of the vine.
My son found one very young tendril surmounted by traces of floral organs, exactly like those on the summit of the true flower-peduncle at the same early age. Passiflora gracilis. This well-named, elegant, annual species differs from the other members of the group observed by me, in the young internodes having the power of revolving.
H. M. July 7, 1st circle was made in 6 18 8, 2nd 6 53 9, 3rd 6 30 As long as a plant remains under the same conditions, the rate is often remarkably uniform, as with the Hop, Mikania, Phaseolus, &c. The Scyphanthus made one revolution in 1 hr. 17 m., and this is the quickest rate observed by me; but we shall hereafter see a tendril-bearing Passiflora revolving more rapidly.
I repeated the experiment made on the Echinocystis, and placed several plants of this Passiflora so close together, that their tendrils were repeatedly dragged over each other; but no curvature ensued. I likewise repeatedly flirted small drops of water from a brush on many tendrils, and syringed others so violently that the whole tendril was dashed about, but they never became curved.
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