Abstract
THIS forms the fourth part of A. F. W. Schimper's “Botanische Mittheilungen aus den Tropen,” and is devoted to the description and illustration of the various adaptations for climbing exhibited by native Brazilian plants observed on the spit. Following Darwin, the author distinguishes four different classes of climbing plants, according to the manner in which they climb; but his four classes are not quite the same. Darwin divided them into those having stems which twine spirally round a support; those which climb by means of irritable organs; those which climb by means of hooks; and those which climb by means of roots. Darwin's investigations, it will be remembered, were chiefly directed to the elucidation of the phenomena exhibited by twiners, and such plants as climb by means of tendrils. Schenck treats in a general way of all four classes of climbers; and his work is more in the nature of a text-book than an account of experimental research. He divides climbing plants into Spreizklimmer, Wurzelkletterer, Windepflanzen, and Rankenpflanzen, corresponding nearly to the hook, root, twining, and tendril climbers of Darwin and others. But the Spreizklimmer include all climbing plants that neither twine nor possess either irritable climbing organs or clinging roots, whether armed or unarmed. Thus the least organised of climbing plants are those having weak, slender, rampant stems and branches which grow up among other plants and rest upon them without any other means of support; whilst the most perfectly developed climbing plants are those provided with highly sensitive nutating tendrils, such as the Cucurbitaceæ and the Passifloraceæ. it is difficult to find an exact English equivalent for “Spreizklimmer,” but “incumbent climbers” might be employed to designate this class. Twiners revolve with the sun, as the hop (Humulus Lupulus), or against the sun, as the scarlet-runner bean (Phaseolus vulgaris) but Schenck agrees with Darwin and other observers that they are not sensible to contact. It is only the plants classed as tendril-climbers that exhibit this property; and this irritability is developed both in caulomes and in phyllomes—that is in branches and in leaves, more or less modified for the purpose. In England there are only three woody climbers, namely: the ivy, a root-climber; the honeysuckle, a twiner; and Clematis vitalba, a leaf-stalk climber; but in Brazil, and in other tropical countries, they are exceedingly numerous, and present a great variety of adaptations to this end. Dr. Schenck, however, does not confine himself to Brazilian forms. He briefly reviews all the types that have come under his observation. Plants climbing by means of tendrils (irritable organs), conceived in the widest sense, are classified according to the organs, or parts of the organs, by means of which they climb. First he takes the leaf-climbers, which climb by means of sensitive revolving leaflets (Fumaria), by the petioles (Clematis and Tropæolum), by the tips of the leaves (Tillandsia and Flagellaria). Then come the leaf-ten- dril climbers proper, such as Pisum sativurn and Cobæa scandens. But the almost peculiarly tropical branch- climbers, plants climbing by means of modified caulomes (branches or inflorescences), present the most singular forms. Dr. Schenck divides them into branch-climbers proper, which have elongated naked or leafy revolving branches clasping the branches of other plants; hook- climbers, which develop hook or claw-like supports; “watch-spring” climbers and thread-climbers. The grape-vine and passion-flower are classed under the last. The climbing organs of the “watch-spring” type are very curious. They are naked, attenuated branches, which roll up in one plane, forming a loose elastic spiral, between the coils of which the support is caught. The spirals usually thicken only at the point of contact, thereby effecting a firm hold of the support. Dr. Schenck does not enter deeply into the anatomy of climbing organs, though he states that differentiation of the tissues of sensitive organs only takes place after contact. The plates are all devoted to the illustration of the external morphology of climbing organs. A systematic list of genera containing climbing species is given, and there is also a chapter on the geographical distribution of climbing plants.
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HEMSLEY, W. Climbing Plants1. Nature 47, 514–515 (1893). https://doi.org/10.1038/047514a0
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DOI: https://doi.org/10.1038/047514a0