Rewm'ches on Growth and Movement in Plants. 383 



the current by means of a rheostat. The experimental subject was a flower- 

 bud of growing Crinum. It was held by a clamp, a little below the region of 

 growth. Stimulus was applied below the clamp so that the transmitted 

 effect had to pass through the securely held tissue. A feeble stimulus was 

 applied on one side, at the indifferent point about 3 cm. below the region of 

 growth. The indirect stimulus reached the region of growth on the same 

 side, bringing about an acceleration of growth with expansion and convexity, 

 the resulting movement being negative or away from the stimulus. The 

 latent period was 10 seconds, and maximum negative movement was com- 

 pleted in the further course of 10 seconds, after which there was a recovery 

 in the course of 75 seconds. A stronger stimulus gave a larger response ; but 

 when the intensity was raised still higher, the hydro-positive was overtaken 

 by the excitatory negative impulse within 15 seconds of the commencement 

 of the positive response ; the convex was then succeeded by the concave 

 curvature (fig. 9). I have obtained similar negative and positive curvatures 



Fig. 9. — Effect of indirect stimulation on growth curvature, a, diagrammatic repre- 

 sentation : continuous arrow represents indirect stimulation; curved"arrow the 

 induced negative curvature ; dotted arrow indicates direct application of stimulus ; 

 and dotted curve the positive curvature, h, indirect stimulation of moderate 

 intensity : S, S' induced negative tropic effect (movement away from stimulated 

 side) ; stronger stimulus S" gave rise to negative followed by positive. {Crinum.) 



with other plant-organs under various forms of stimuli. Thus the indirect 

 effect of continuous application of light of feeble intensity was to increase 

 negative curvature in a stem of Dregea volubilis. Direct application of light 

 on the region of growth gave, on the other hand, a positive curvature. 



Thus, while the direct effect of unilateral stimulation is to induce a positive 



