PAGE 



Il6 



xvi CONTENTS 



thermal stimulation — Effect of direct and indirect stimulation 

 on growing organ — Effect of indirect and direct radio -thermal 

 and electric stimulation — Electric response to direct and indirect 

 stimulation — Laws of Effect of Direct and of Indirect Stimula- 

 tion ..••••••••• 



CHAPTER XIII 



DIA-PHOTOTROPISM AND NEGATIVE PHOTOTROPISM 



Neutrahsation caused by conduction of excitation across the organ- 

 Complete neutrahsation in thin organs — Fatigue-relaxation of 

 directly stimulated proximal side — Negative phototropic curva- 

 ture under prolonged unilateral action of strong light— Supposed 

 phototropic ineffectiveness of sunhght — So-called negative 

 phototropism of roots — The Root-Recorder — Effect of unilateral 

 stimulation of root-tip — Effect of indirect unilateral stimulation 

 of shoot — Effect of simultaneous stimulation of the tip and of the 

 growing region of root — Phototropic curvature of root of Sinapis 

 — Preliminary positive curvature transformed into negative by 

 transverse conduction of excitation . . . . -133 



CHAPTER XIV 



THE PHOTOTROPIC CURVE AND ITS CHARACTERISTICS 



Susceptibility for excitation not constant but variable at different 

 parts of phototropic curve — The simple phototropic curve- 

 Effect of stimulation on subtonic organ — Complete phototropic 

 curve of a pulvinated organ — Four distinct stages in the complete 

 curve of a growing organ , . . . . . . .148 



CHAPTER XV 



THE PHOTONASTIC PHENOMENA 



Phototropic and photonastic effects — Fall of leaflet of Averrhoa 

 when acted on by light from above or below — Exhibition of 

 opposite effect by leaflet of Mimosa — Photic Stimulator— Effect 

 of moderate photic stimulation of upper surface of pulvinus of 

 Mimosa — Effect of stronger light — Velocity of transmission 

 through upper half of organ — Effect of light on lower half of 

 pulvinus — Characteristic effects of appHcation of strong light 

 on upper and lower halves of the organ— Physiological detection 

 of gradation of excitability in lower half of pulvinus — Erectile 

 twitch of hydraulic impulse — Effect of radio-thermal stimulation 

 of upper half of pulvinus — Effect of strong photic stimulation of 

 lower half of pulvinus — Response of leaflet of Averrhoa to 

 strong hght from above — Effect of strong light applied below 

 — Effect of strong light on leaflet of Mimosa applied above and 

 be'ow^Universal laws of responsive movements of plant-organs 

 — Mechanical and electric responses of pulvinated and growing 



