xxvi PLANT RESPONSE 



CHAPTER XLVII 



TORSIONAL RESPONSE TO HELIOTROPIC AND GEOTROPIC STI- 

 MULUS : AUTONOMOUS TORSION AND ITS VARIATIONS 



I'AGK 



Torsional effect — Method of recording torsional response — Torsional re- 

 sponse under the lateral action of light — Torsional response to other 

 forms of lateral stimulation — Torsional response of compound strip of 

 ebonite and stretched india-rubber — Modification of torsional response 

 by artificial variation of the relative excitabilities of the two halves — ■ 

 Laws of torsional response — Demonstration of differential geotropic ex- 

 citation in a dorsi-ventral organ — Torsional response to lateral geotropic 

 stimulation — Modification of torsional geotropic response by artificial 

 variation of differential excitability — Autonomous torsion : Effect of 

 temperature — Effect of light — Effect of electrical current — Effect of 

 gravity — The twining of stems ........ 656 



CHAPTER XLVIII 



NYCTITROPIC MOVEMENTS 



Comparison between nyctitropic and autonomous pulsations — Diurnal move- 

 ment of plagiotropic stem — Supposed distinction between nyctitropic 

 and other movements of response to stimulus of light Diurnal response 

 of leaf of Biophyttim — Diurnal response of primary petiole of Mimosa — 

 Periodic impulses acting on the leaf — Periodic impulses contributed by 

 the plant as a whole — Other modes of exhibition of diurnal periodicity 

 of hydrostatic tension — Forced vibration and its periodic after-effects — 

 Physical analogue — Impressed periodic vibrations in organ originally 

 radial ............ 676 



CHAPTER XLIX 



ON PULSATORY RESPONSE AND SWIMMING MOVEMENTS AS 

 INITIATED AND MODIFIED BY LIGHT AND OTHER FORMS 

 OF STIMULUS 



Investigations on the influence of light on the lateral leaflet of Desmodium 

 gyrans : (a) in sub-tonic condition ; (/>) in normal tonic condition — 

 Changes induced in existing anisotropy of Desiiiodiiim leaflets — Reversal 

 under intense stimulation seen in all forms of response — The swimming 

 movements of ciliated organisms —Fundamental resemblance between 

 the swimming responses and the ordinary heliotropic responses in radial 

 organs — Phototactic movements : (a) Two natural types of responsive 

 movements ; (6) Responsive movement positive, negative, or inter- 

 mediate, according to intensity of stimulation —Directive action of light 

 — Thermotaxis — Galvanotaxis — Chcmotaxis ..... 689 



