Page:Life Movements in Plants.djvu/122

92 consequent diminution of amplitude of response. There is thus an increased fatigue with diminished period of rest. This is illustrated in Fig. 38, where the first two responses are at intervals of 15 min.; the resting interval was then reduced to 10 min., the response undergoing a marked diminution. Conversely, by increasing the resting interval, first to 12 and then to 15 min., the extent of fatigue was reduced and then abolished.

Experiment 31.—From the above experiment it would appear that since the incompleteness of recovery induces fatigue, hastening of recovery would remove it. With this idea I tried various methods for quickening the recovery of the excited leaf. The application of a constant electric current was found to have the desired effect. Two electrodes for introduction of current were applied, one on the stem and the other on the petiole, at some distance from the pulvinus. In order to avoid the excitatory effect of sudden application, the applied current should be in-

39.—Action of constant current in removal of fatigue by hastening recovery; N, curve of response in fatigued specimen; C, after passage of current.