/ 



STIMULATION OF THE TENDRIL 93 



growth became greatly enhanced, even more than three 

 times the normal. This is clearly seen in the record (upper 

 half of the figure) taken 20 minutes after stimulation, the 

 curve being far more erect than that of the normal rate of 

 growth before stim^ulation. 



The effects of indirect and direct electric stimulation 

 of the tendril are, therefore, as follows : 



1. Indirect stimulation induces sudden enhancement 



of the rate of growth, followed by recovery to the 

 normjal rate. 



2. Direct stimulation induces a retardation of the rate 



of growth. 1 he after-effect of direct stimulation of 

 moderate intensity is a short-lived enhancement of 

 the rate of growth above the normal. 



I now proceed to show that mechanical stimulation 

 induces effects which are ver}^ similar. 



Effects of Direct and Indirect Mechanical 



Stimulation 

 Experiment 54. Effect of direct mechanical stimulation. 

 I took a growing tendril of Cucurbita, and after taking a 

 record of its normal rate of growth, subjected it to feeble 

 mechanical stimulation by rubbing its different sides. The 

 im.mediate effect was a retardation from the normal rate of 

 0-44 }x to 0-20 [X per second, the reduced rate being less 

 than half the normal. The tendril recovered its normal 

 rate of growth after the feeble stimulation ; in fact, the 

 effect after 15 minutes was even a shght acceleration above 

 the normal, the growth-rate being 0-59 [j, per second. The 

 results are given in the following table : 



Table XII. — The Immediate and After-Effect of Mechanical 

 Stimulation on Growth of Tendril (Cucurbita). 



Normal rate of growth 



Retarded rate immediately after stimulation 



Recovery and enhancement after 15 minutes 



0-44 ;« per second 



0-20 {.i ,, 



The effect of unilateral stimulation will be next considered, 



