tendril of Passiflora becomus hooked or coiled, the concave being the excited side. From what has been said, the unexcited convex side will relatively be the more excitable.
Experiment 11.—I took a specimen of hooked tendril, and excited it by an electric shock. The response was by the greater contraction of the more excitable convex side, on account of which the curved specimen tended to open out. The record of this response is seen in Fig. 11;
the apex-time was nearly two minutes, and the recovery was completed in the further course of 15 minutes.
From the responses of organs rendered anisotropic by the differential action of the environment we pass to others which show certain amount of anatomical and physiological differentiation between their upper and lower sides. I find that many petioles of leaves show movement in response to stimulus. Many pulvini, generally regarded as
