Page:Life Movements in Plants.djvu/114

84 LIFE MOVEMENTS IN PLANTS relation between a definite testing stimulus and the resulting response with its time-relations, which is secured by my Resonant Recorder with the standardised electrical stimulator. In carrying out this investigation I first took the record of normal response of an intact leaf on a fast moving plate. A second record, with the same stimulus, was taken after the removal of the upper half of the pulvinus, having taken the necessary precautions that have been described. Comparison of the two records (Fig. 32) shows that the only FIG. 32.-Effect of amputation of upper half of pulvinus. Upper record gives normal response before amputation, and the lower, response after amputation (Successive dots at intervals of 0-1 sec.). Apex-time 11 sec., in both. difference between them is in the exhibition of slight diminution of excitability due to operation. But, as regards the latent period and the quickness of attaining maximum fall, there is no difference between the two records before and after the amputation of the upper half. The upper part of the pulvinus is thus seen practically to have little influence in hastening the fall. EFFECT OF REMOVAL OF THE LOWER HALF. Earperiment 25.--The shock-effect caused by the amputation of the lower half was found io be very great, and it required a long period of rest before the upper half regained its excitability. The excitatory reaction of the upper half