TWINING OF TENDRILS 293 



(2) Direct stimulatiou induces a retardation of the rate 

 of growth which may culminate into an actual 

 contraction. The after-effect of direct stimulus of 

 moderate intensity is an enhancement of the rate 



ofijrowth. 



The experiments describ.Ml above demonstrate the effects 

 ot tlireet and indirect electrical stimulus. I shall now 

 proceed to show that mechanical stimulus induces effects 

 which are similar to those of electric stimulus. 



EFFECTS OF DIRECT AND INDIRECT MECHANICAL 

 STIMULUS. 



Kff'ect of Direct meclianical. stimulus : Experiment 108. — 

 In this case I took a tendril of Gucurhita, and attached 

 it to the ordinary High Magnification Crescograph, the 

 record of which gives the absolute rate of its normal 

 growth, and the induced variation of that rate. The tendril 

 was stimulated mechanically by simultaneous friction of its 

 different sides. The immediate effect was a retardation of 

 growth, the reduced rate being less than half the normal. 

 There was a recovery on the cessation of the stimulus ; the 

 rate of growth was even slightly enhanced after an interval 



TABLE XXVI. — SHOWING THE IMMEDIATE AND AFTER-EFFECT OK MECHA- 

 NICAL STIMULATION ON TENDRIL {CuCurbitu), 



Normal rate of growth ... ... ... 0'44 H- per sec. 



Retarded rate iniinediutely after stimulation ... 0'20 M- „ „ 



Hecoverv and enhancement after 15 minutes ... 0'50 /a ,, ,, 



of 15 minutes. Table XXYI shows the immediate and 

 after-effects of mechanical stimulation on growth. 



