TWINING OF TENDRILS 



291 



Effect of Indirect Stimulus : Experiment 106. — The 



growth of the tendril was exactly 



balanced, and the record became 



horizontal. Indirect stimulus was 



next applied below the clamp ; this 



is seen to upset the balance, with 



the resulting up-curve which 



indicates a sudden acceleration of 



growth above the normal. This 



acceleration took place within ten 



seconds of the application of 



Fig. 103.— Record by Method Stimulus, and persisted for three 



of Balance, showing acceiera- minutes ; after this the normal rate 



tion of growth of tendril (up- ^^^ ^^^^,^^ became restored, as seen 



curve ■) induced by indirect sti- 



muiation. {Cucurbita.) by the balanced record once more 



becoming horizontal (Fig. 103). 



Effect of Direct Stimulus : Experiment 107. — The in- 

 cipient contraction induced by direct stimulation is so 

 great that the record obtained by the delicate method of 

 balance cannot be kept within the plate. I, therefore, 

 took the ordinary growth-curve on a moving plate. The 

 first part of the curve represents normal growth ; stimulus 

 of feeble electric shock was applied at the highest point of 

 the curve. This is seen (Fig. 104) to induce an immediate 

 contraction and reversal of the curve which persisted for 

 two and half minutes, after which growth was slowly 

 renewed. Tht^ most interesting fact regarding the after- 

 effect of stimulus is that the rate of growth became actually 

 enhanced to three times the normal. This is clearly seen 

 in the record (upper half of the figure) taken 20 minutes 



