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Show 332 DARWINIAN A. of a memoir communicated to the Linm:ean Society in 1865, and published in the ninth volume of its Journal. There was an extra impression, but, beyond. the circle of naturalists, it can hardly have been m\lch known at first-hand. Even now, when it is made a part of the general Darwinian literature; it is unlikely to be as widely read . as the companion volume which we have been reviewing; although it is really a more readable book, and well worthy of far more extended notice at our hands than it can now receive. The reason is obvious. It seems as natural that plants should climb as it does unnatural that any should take animal food. · Most people, knowing that some plants" twine with the sun," and others "against the sun," have an idea that the sun in some way causes the twining; indeed, the notion is still fixed in the popular mind that the same species twines in opposite directions north and south of the equator. Readers of this fascinating treatise will learn, first of all that the sun has no infl..uence over such move-ments' directly, and that its indirect infl..uen.ce is com-monly adverse or disturbing, except the heat, which quickens vegetable as it does animal life. Also, that climbing is accomplished by powers and actions as unlike those generally predicated of the vegetable kingdom as any which have been brought to view in the preceding volume. Climbing plants" feel" as well as "grow and live;" and they also manifest an automatism which is perhaps more wonderful than a response by visible movement to an external i:ritatio~. . Nor do plants grow up their supports, as IS unthmkmgly supposed; for, although only growing or newly-grown INSECTIVOROUS AND CLIMBING PLANTS. 333 parts act in climbing, the climbing and the growth are entirely distinct. To this there is one exception-an instructive one, as showing how one action passes into another, and how the same result may be brought about in different ways-that of stems which climb by rootlets, such as of ivy and trumpet-creeper. I-Im·e the stem ascends by growth alone, taking upward direction, and is fixed by rootlets as it grows. There is no better way of climbing walls, precipices, and large tree-trunks. But small stems and similar supports are best ascended by twining; and this calls out powers of another and higher order. The twining stem does not grow around its support, but winds around it, and it does this by a movement the nature of which is best observed in stems which have not yet reached their support, or have overtopped it and stretched out beyond it. Then it may be seen that the extending summit, reaching farther and farther as it grows, is making free circular sweeps, by night as well as by day, and irrespective of external circumstances, except that warmth accelerates the movement, and that the general tendency of young stems to bend toward the light may, . in case of lateral illumination, accelerate one-half the circuit while it equally retards the other. The arrest of the revolution where the supporting body is struck, while the portion beyond continues its movement, brings about the twining. As to the proximate cause of this sweeping motion, a few simple experiments prove that it results from the bowing or bending of the free summit of the stem into a more or less horizontal position (this bending being successively to every point 15 |