94 chap. x. effect of mechanical stimulation 



Effect of Direct Unilateral Mechanical 



Stimulation 



The previous experiment gives the effect of diffuse 

 mechanical stimulation of the tendril. I now describe 

 the effect of direct unilateral stimulation applied at the 

 growing region. 



Experiment 55. — The tendril of Cucurbita was mounted 

 on the Balanced Crescograph, and the record obtained with 

 a single recording lever. The first part of the curve shows 



Fig. 47. Positive curvature of tendril of Cucurbita 

 under stimulus of unilateral contact at x. 



the horizontal record of balanced growth. Unilateral 

 contact-stimulation w^as effected between two successive 

 dots (which were at intervals of 3 seconds) with the object 

 of not disturbing the record. Positive curvature was 

 induced in the course of about 10 seconds and attained its 

 climax in about 2 minutes, after which the tendril slowly 

 recovered, as shown in the horizontal curve in the upper 

 part of the record (fig. 47). Feeble stimulation is attended 

 by a recovery within a short time. Under strong stimula- 

 tion the curvature becomes more persistent. 



