Researches on Growth and Movement in Plants. 385 



stronger stimulation. Unilateral application of stimulus will bring about a 

 contraction of the proximal side due to the direct effect of stimulation, and 

 an expansion on the distal side due to indirect effect. 



Expt. 8. Effect of Diffuse Mechanical Stimulation on the Growth of Tendril. 

 — I took a growing tendril of Cucurbita, and, after obtaining record of its 

 normal rate of growth, subjected it to feeble mechanical stimulation by 

 rubbing its different sides. The immediate effect was a retardation from the 

 normal rate of 0'44 /m per second to 0-20 /x per second. The tendril recovered 

 its normal rate of growth after the feeble stimulation ; in fact, the effect, 

 after 15 minutes, was even a slight acceleration above the normal, the growth 

 rate being 0"59 /x, per second. The contraction of the directly excited side 

 and the expansion due to indirect stimulation of the distal side will give an 

 explanation of Fitting's observation* that in a unilaterally stimulated 

 tendril there is (1) an acceleration of growth on the convex side, and (2) a 

 contraction on the concave side. Fitting noticed that the tendril became 

 straightened by the active renewal of growth on the excited side. 



Fig. 10. — Positive curvature of tendril of Cacvrhita under unilateral stimulas of contact 



at X . 



I give here a record obtained with a single recording lever (magnification 

 50 times), showing the response to short unilateral contact in a tendril of 

 Cucurbita. Positive curvature was induced in about 15 seconds and 

 attained its climax in 2^ minutes, after which the tendril slowly commenced 

 its recovery, which was completed in 12 minutes (fig. 10). Feeble stimula- 

 tion is attended by a recovery within a moderate period of time. Under 

 strong stimulation the curvature becomes more persistent. 



12. Galvanotrofism and Electrotropism. 



I have demonstrated the retarding effect of the cathode and the accele- 

 rating effect of the anode on growth. Unilateral application of anode 



* Pfeffer, ilnd., vol. 3, p. .57. 



