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Updated: June 20, 2025
It should also be observed, that the possession of leaves with sensitive petioles, and with the consequent power of clasping an object, would be of comparatively little use to a plant, unless associated with revolving internodes, by which the leaves are brought into contact with a support; although no doubt a scrambling plant would be apt, as Professor Jaeger has remarked, to rest on other plants by its leaves.
By this definition, spines, hooks and rootlets, all of which are used for climbing, are excluded. True tendrils are formed by the modification of leaves with their petioles, of flower-peduncles, branches, and perhaps stipules.
Plants 1 ft. high, bearing a cluster of flowers, are thus annually obtained at Kew. When planted out, the leaves and spine-cushions are farther apart. Stem erect, woody, branching freely, the branches bearing oval, acuminate, fleshy, wavy-edged, green leaves, with short petioles, and a pair of spines in the axil of each. Spine-cushions on old stems crowded with stout, brown spines.
Not only leaves, but petioles of many kinds, some flower-peduncles, often decayed twigs of trees, bits of paper, feathers, tufts of wool and horse- hairs are dragged into their burrows for this purpose. I have seen as many as seventeen petioles of a Clematis projecting from the mouth of one burrow, and ten from the mouth of another.
The most interesting cases are those furnished by the forms which some plants bear only while young, and which evidently connect them with allied species, in which the same features may be seen in the adult state. Some species of the genus Acacia bear bipinnate leaves, while others have no leaves at all, but bear broadened and flattened petioles instead.
The movements can be made visible by the same method as was used for the stem of the Morning-Glory. Tendrils and leaf petioles are often sensitive to the touch. If a young leaf stalk of Clematis be rubbed for a few moments, especially on the under side, it will be found in a day or two to be turned inward, and the tendrils of the Cucumber vine will coil in a few minutes after being thus irritated.
I gently rubbed with a thin twig the lower surfaces of two young petioles; and in 2 hrs. 30 m. they were slightly curved downwards; in 5 hrs., after being rubbed, the end of one was bent completely back, parallel to the basal portion; in 4 hrs. subsequently it became nearly straight again.
Some of these objects, such as the petioles just named, feathers, &c., are never gnawed by worms. The surfaces by which these leaves are articulated to the branches are shaped in as peculiar a manner as is the joint between the leg-bones of a quadruped; and if these surfaces had been in the least gnawed, the fact would have been immediately visible, but there was no trace of gnawing.
This anomaly was however readily explained as soon as the thick basal part was examined; for in 78 out of 103 petioles, this part had been gnawed by worms, just above the horse-shoe shaped articulation.
In the midst of a mass of blackish debris, a, organic and inorganic, and immersed in an amorphous and transparent gangue, we find a few recognizable fragments, such as thick-walled macrospores, b, of various sizes, bits of flattened petioles, c, pollen grains, d, debris of bark, etc.
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