422 



LIFE MOVEMENTS IN PLANTS 



following records, represented by a down curve, and a 

 retardation by an up-curve. 



Effect of feeble stimulus: Experiment 161. — I first studied 

 the effect of feeble stimulus. This was secured by decreas- 

 ing the energy of sparks of the radiator. The response 

 was an acceleration of rate of growth as seen in figure 

 156a. The analogy of this with the accelerating effect of 

 sub-minimal intensity of light (p. 224) is very remarkable. 



Effect of strong stimulus : Experiment 162.— The maxi- 

 mum energy^' radiated by my transmitter, as stated before, 

 was only moderate. In spite of this its effect on plants w.as 

 exhibited in a very striking manner. The balance was 



Fig. 156. — Record ot responses to electric wave bj' the Balanced Crescograph 

 (a) response to feeble stimulus by acceleration of growth, (b) response to strong 

 stimulus by retardation, (c) responses to medium stimulation— retardation followed 

 by recovery. Down-curve represents acceleration, and up-curve retardation of growth: 

 (Seedling of wheat.) 



immediately upset, indicating a retardation of the rate of 

 growth. The latent period, i.e., the interval between the 



