CONTENTS XXI 



CHAPTER XXVI 



THE EXCITATORY CHARACTER OF SUCTIONAL RESPONSE 



PAGE 



Propagation of excitatory wave in plant attended by progressive movement of 

 water Hydraulic response to stimulus The Shoshungraph Direct and 

 photographic methods of record Responsive variations of suction under 

 physiological modifications induced by various agents Effects of lower- 

 ing and raising of temperature Explanation of maintenance of suction, 

 when root killed Effect of poison influenced by tonic condition Effect 

 of anaesthetics on suctional response Excitatory versus osmotic action 

 Stimulation by alternating induction -shocks Terminal and sub-ter- 

 minal modes of application Three modes of obtaining response-records, 

 namely (i) the unbalanced, (2) the balanced, (3) the over-balanced 

 Renewal of suction previously at standstill, by action of stimulus- -Re- 

 ponsive enhancement of suction by stimulus After-effect of stimulus 

 Diminution of latent period as after-effect of stimulus Response under 

 over-balance Response under sub-terminal stimulation Variation of 

 response under seasonal changes 365 



CHAPTER XXVII 



RESPONSE TO STIMULUS OF LIGHT 



Heliotropic plant movements reducible to fundamental reaction of contrac- 

 tion or expansion Various mechanical effects of light in pulvinated and 

 growing organs Electrical response induced by light not specific, but 

 concomitant to excitatory effects Electrical response of plant to light 

 not determined by presence or absence of chloroplasts Effect of 

 unilateral application of stimulus on transversely distal point Positive 

 response due to indirect effect and negative to transmission of true 

 excitation Mechanical response of leaf of Mimosa to light applied on 

 upper half of pulvinus Mechanical response consists of erection or 

 positive movement, followed by fall or negative movement Electrical 

 response of leaf of Mimosa to light applied on upper half of pulvinus ; 

 induction in lower half of pulvinus of positivity followed by negativity 

 Longitudinal transmission of excitatory effect, with concomitant galvano- 

 metric negativity --Direct effect of light and positive after effect 

 Circumstances which are effective in reversing normal response Plants 

 In slightly sub-tonic condition give positive followed by negative response 

 Exemplified by (a) electrical and (b) growth response Examples of 

 positive response to light Periodic variation of excitability Multiple 

 mechanical response under light Direct and after-effect Multiple 

 electrical response under light, with phasic alterations of ( + + ) or 

 ( + + ) After-effects ; unmasking of antagonistic elements, either 

 phis or minus Three types of after-effects 392 



