The Movements and Habits of Climbing PlantsDarwin, Charles
Science
The Movements and Habits of Climbing Plants
Darwin, Charles
Climbing plants; Geotropism; Plants; Plants -- Irritability and movements
In the allied Eccremocarpus the internodes, petioles, and much-branched
tendrils all spontaneously revolve together. The tendrils do not as a
whole turn from the light; but their bluntly-hooked extremities arrange
themselves neatly on any surface with which they come into contact,
apparently so as to avoid the light. They act best when each branch
seizes a few thin stems, like the culms of a grass, which they afterwards
draw together into a solid bundle by the spiral contraction of all the
branches. In Cobæa the finely-branched tendrils alone revolve; the
branches terminate in sharp, hard, double, little hooks, with both points
directed to the same side; and these turn by well-adapted movements to
any object with which they come into contact. The tips of the branches
also crawl into dark crevices or holes. The tendrils and internodes of
Ampelopsis have little or no power of revolving; the tendrils are but
little sensitive to contact; their hooked extremities cannot seize thin
objects; they will not even clasp a stick, unless in extreme need of a
support; but they turn from the light to the dark, and, spreading out
their branches in contact with any nearly flat surface, develop discs.
These adhere by the secretion of some cement to a wall, or even to a
polished surface; and this is more than the discs of the _Bignonia
capreolata_ can effect.
The rapid development of these adherent discs is one of the most
remarkable peculiarities possessed by any tendrils. We have seen that
such discs are formed by two species of Bignonia, by Ampelopsis, and,
according to Naudin, {179} by the Cucurbitaceous genus _Peponopsis
adhærens_. 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. The growth of these cellular out-growths depends, (except in
the case of the _Haplolophium_ and of one species of Ampelopsis,) on the
stimulus from contact. It is a singular fact that three families, so
widely distinct as the Bignoniaceæ, Vitaceæ, and Cucurbitaceæ, should
possess species with tendrils having this remarkable power.
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