Plants, it has been vaguely asserted, differ from animals by not having the power of movement. Rather should it be stated that plants acquire and display this power when it is to their advantage. This will be found to be of comparatively rare occurrence, as they are affixed to the ground, and food is brought to them by the air and rain. Evidence of the very high position a plant may attain in the scale of organization may be seen when we look at one of the more perfect tendril-bearers. As a polypus adjusts its tentacula for action, so a plant places its tendrils. If the tendril be displaced, it sets to work to right itself. Acted on by the light, it bends towards or from it, or disregards it altogether, whichever course may be the most advantageous. For several days the tendrils or internodes of the plant, or both, spontaneously or otherwise revolve with a steady motion. But should they strike some object, they curl quickly around it, grasp it with wonderful firmness, and in the course of a few hours contract into spirals, dragging up the stems, and forming most excellent springs. All external movements now cease, and by growth the tissues soon become surprisingly strong and durable. Such a movement, as has just been considered, is a widely prevalent one in plants, and is essentially of the same nature as that of the stem of a climbing plant, which successively bends to all points of the compass, so that the tip is made to revolve. This movement has been called _revolving nutation_ by some writers, and _circumnutation_ by others. In the case of the circumnutating movement of the tip of the radicle of some plants, there can be no doubt that it is it that affords the radicle some slight assistance in penetrating the ground. But whether or not a radicle, when surrounded by softened earth, is aided in making a passage for itself by circumnutating, one thing is certain, that is, that this movement, by guiding the radicle along a line of least resistance, can hardly fail to be of high importance. Should, however, a radicle in its downward growth break obliquely into any crevice, or an opening left by a decayed root, or one made by the larva of an insect, and more especially by worms, the circumnutating movement of the tip will materially aid it in following such open passages. Not only our own observation, but also those of such eminent authorities as Darwin and Hensen, conclusively show that roots commonly run down the old burrows of worms.