xii PLANT kKSPONSK 



and electrical response — True excitation has a concomitant negative 

 turgidity-variation, negative mechanical response or fall, and galvano- 

 metric negativity— These are true physiological responses, and are 

 abolished at death— Abnormal positive mechanical and electrical 

 responses brought about by positive turgidity-variation— Direct and 

 indirect effects of stimulation — Discrimination of differences of excit- 

 ability by electric test — Excitability of plant-tissues in general— Re- 

 sponsive power characteristic of matter 29 



CHAPTER IV 



ON CONDITIONS FAVOURABLE TO THE CONSPICUOUS 

 EXHIBITION OF MECHANICAL RESPONSE 



Differences of degree of motile sensibility in sensitive plants so called — 

 Response of anisotropic organ brought about by differential contraction 

 — Production of response by artificial variation of turgidity — Variation 

 and counter-variation of turgescence, causing two opposite responsive 

 movements — Differences between hydrostatic and true excitatory effects 

 — Distinction of plants as ordinary and sensitive, arbitrary — Sensitive 

 plants may be excited, yet give no mechanical response — Certain con- 

 ditions necessary to exhibition of differential response — Balanced action 

 as result of diffuse stimulus on radial organ — Slight differential contraction 

 of pulvinus magnified by long petiolar index 43 



CHAPTER V 



MECHANICAL RESPONSE IN ORDINARY LEAVES 



Pulvinoid and pulvinus — Demonstration of mechanical response in ordinary 

 leaves — Response of Artocarpus similar to that of Biophytum — Response 

 to stimulus, even in old tissues, by expulsion of water — Localisation of 

 motile organ in ordinary leaves — Conducting properties of various tissues 

 —Lamina is not the perceptive organ —Response in ordinary leaves, 

 though sluggish, yet comparable in extent to that of Mimosa —Peculiar 

 phenomenon of fatigue-reversal seen in Mimosa observed also in ordinary 

 plants — Periodic reversals ......... 53 



CHAPTER VI 



LONGITUDINAL RESPONSE OF RADIAL ORGANS 



Absence of lateral response movements in radial organs due to mutually 

 antagonistic effects of equal contractions of diametrically opposite sides 

 — Lateral response in radial stem of Walnut under unilateral stimulation 

 — Also in pistil of Musa— Diffuse stimulation of radial organ causes 

 longitudinal contraction — The ' Kunchangraph ' — Longitudinal contrac- 

 tion of stamens of Cytierea not unique— Similar longitudinal responses 



