I was led to this subject by an interesting, but too short, paper by Professor Asa Gray on the movements of the tendrils of some Cucurbitaceous plants. My observations were more than half completed before I became aware that the surprising phenomenon of the spontaneous revolutions of the stems and tendrils of climbing plants had been long ago observed by Palm and by Hugo von Mohl, and had subsequently been the subject of two memoirs by Dutrochet. Nevertheless I believe that my observations, founded on the close examination of above a hundred widely distinct living plants, contain sufficient novelty to justify me in laying them before the Society.

Climbing plants may be conveniently divided into those which spirally twine round a support, those which ascend by the movement of the foot-stalks or tips of their leaves, and those which ascend by true tendrils,–these tendrils being either modified leaves or flower-peduncles, or perhaps branches. But these subdivisions, as we shall see, nearly all graduate into each other. There are two other distinct classes of climbing-plants, namely those furnished with hooks and those with rootlets; but, as such plants exhibit no special movements, we are but little concerned with them; and generally, when I speak of climbing plants, I refer exclusively to the first great class.

Part I.–SPIRALLY TWINING PLANTS.

This is the largest subdivision, and is apparently the primordial and simplest condition of the class.