

CONTENTS XXV 



l'AGE 



tropic curvature induced by stimulation of the tips of root and shoot — 

 Intermediate phases between positive and negative heliotropic response : 

 (a) neutralisation by transverse transmission ; (b) neutralisation by 

 transverse transmission, with multiple response — Localised sensitiveness 

 to light and transmission of excitatory effect — Negative heliotropism of 

 a radial organ — Gradual transition from positive to negative, through 

 intermediate phase of neutrality — Apparent heliotropic insensitiveness of 

 certain tendrils — Negative heliotropism of tendril of Vitis . . . 597 



CHAPTER XLIV 



EFFECT OF INVISIBLE RADIATION AND EMANATIONS 



Effect of temperature and its variations — Demonstration of fundamental 

 effect of thermal radiation on growth — Response to successive uniform 

 stimuli of thermal radiation — Effect of continuous unilateral stimulation 

 — Effect of electrical waves on growth — Response of Mimosa to electric 

 radiation — Action of high frequency Tesla current .... 614 



CHAPTER XLV 



ON PHOTONASTIC PHENOMENA AND ON DIURNAL SLEEP 



Photonasty and para-heliotropism — Response of Tropceolum majus — Re- 

 sponses of plagiotropic stems : {a) Mimosa — (b) Ipomosa — (c) Cucurbita — 

 Daily periodic movements of plagiotropic stems — Responsive movements 

 of pulvinated organs — Pulvinated organs showing positive heliotropic 

 movement : (a) Response of terminal leaflet of Desm odium — (b) Response 

 of leaflet of Robinia ~{c) Responsive movements of leaflets of Erythrina 

 indica and Cliloria tematea — The negative heliotropic type of response : 

 (a) Response of pulvinus of Mimosa — (b) Diurnal sleep of Oxalis — (c) 

 Diurnal sleep of Biophytum — Directive versus non -directive action of 

 light — General view of responsive curvatures induced in different organs 

 by unilateral application of light . . . . . . . .621 



CHAPTER XLVI 



ON DIA-HELIOTROPISM AND DIA-GEOTROPISM 



Difficulty of distinguishing between effect of light and other reactions — 

 Theories of Frank and De Vries — Subsidiary factors: (1) Epinasty and 

 hyponasty ; (2) Effect of gravity ; (3) Effect of suctional activity and 

 of turgescence ; (4) Modification of effect by characteristic limits of 

 flexibility — Discrimination of the part played by heliotropism in the 

 movement of the leaf— Proof of absence of any specific dia-heliotropic 

 tendency in leaves — The lamina not the perceptive organ — Principal 

 types of the response of leaves to stimulus of light — Positive type of 

 response : mango leaf — Negative type of response : leaf of Artocarpus . 640 



