96 CHAP. X. EFFECT OF MECHANICAL STIMULATION 



was made with the proximal side to the right (the proximal 

 side being the side to be directly stimulated), the second 

 connection being made with a distant indifferent point. 

 Similar connections were also made for the second series, 

 the two electric contacts being respectively made with a 



distal point diametrically opposite to 

 the proximal, and with an indifferent 

 point at a distance. A sensitive gal- 

 vanometer was included in the electric 

 circuit for record of the responses at 

 the proximal and distal points. 



Mechanical stimulation was effected 

 by friction applied very near the 

 proximal point. The record first taken 

 was that of the effect on the distal side 

 of this indirect stimiulation. The 

 down-record, followed by recovery, 

 indicates a positive electric variation, 

 indicative of increase of turgor, ex- 

 pansion and enhancement of growth 

 at the distal point. Record was next 

 taken of the effect of the direct stimu- 

 lation on the proximal side. The 

 larger up-response indicates strong 

 galvanometric negativity, indicative of 

 diminution of turgor, contraction and 

 retardation of growth (fig. 49). 

 These phenomena of responsive reaction in the tendri] 

 will be shown to be by no means unique, but similar to 

 those of other organs under all forms of stimulation. The 

 only speciahty in the tendril is that, owing to its structure, 

 the perceptive power of the organ for mechanical stimula- 

 tion is highly developed. 



The following is a brief summary of the facts estabhshed 

 in regard to the responsive characteristics of the tendril, 

 and the tropic curvature induced in it by unilateral 

 stimulation : 



Fig. 49. Electric re- 

 sponse at the distal 

 and proximal sides of 

 a tendril under uni- 

 lateral mechanical 

 stimulation. 



Galvanometric positiv- 

 ity is induced at distal 

 side (down-curve), 

 while galvanometric 

 negativity (up-curve) 

 is exhibited at the 

 proximal side (Vitis 

 quadrangularis). 



