Page:Life Movements in Plants.djvu/64

34 (Fig. 10). Stronger shocks induce greater contraction

with prolongation of the period of recovery. The specimen was afterwards killed by application of poisonous solution of potassium cyanide; this brought about a permanent abolition of response. The experiment just described may be taken as typical of response of radial organs.

In a radial organ contraction takes place equally in all directions; it therefore shortens in length, there being no movement in a lateral plane. But, if any agency renders one side less excitable than its opposite, diffuse stimulation will then induce greater contraction on the more excitable side which will therefore become concave.

Excessive stimulation is found to reduce the excitability of an organ. Under unilateral mechanical stimulation a