CONTENTS xxiii 



CHAPTER XXXVII 



THE RESPONSIVE PECULIARITIES OF THE TIPS OF 

 GROWING ORGANS 



PAGE 



Difference between shoot and root in their response to stimulus of gravity 

 — Difference in character of response between tip and growing region of 

 root — Scope of the investigation — Electrical investigation — Responsive 

 results of: I. Longitudinal transmission of effect of stimulus from tip ; 

 (a) Moderate unilateral stimulation ; (/>) effect of stronger unilateral 

 stimulation — 2. Direct unilateral stimulation of growing region — 

 Moderately strong stimulus — 3. Transverse transmission of effect of 

 stimulus ; (a) moderate stimulation ; (b) stronger stimulation — 

 Mechanical response inferred from observed electrical response — 

 Tabular statement . . . . . . . . . .512 



CHAPTER XXXVIII 



INQUIRY INTO THE LAWS OF RESPONSIVE GROWTH- 

 CURVATURES 



Scope of the investigation : 1. Mechanical response to unilateral stimula- 

 tion of the tips of shoot and root : (a) Moderate stimulus — (/>) Stronger 

 stimulation — 2. Effect of unilateral stimulus, applied at the responding 

 growing region: (a) Moderate stimulus— (6) Strong or long-continued 

 stimulus — Experiments on the direct and indirect effects of stimulus on 

 Mimosa : (a) Direct stimulation — (/?) Indirect stimulation, longitudinal 

 transmission — (1) Indirect stimulation, transverse transmission — The 

 curious response of Ariscema— Table showing responsive effects common 

 to pulvini, pulvinoids, and growing organs — Laws of responsive growth- 

 curvature ............ 524 



CHAPTER XXXIX 



INQUIRY INTO POSITIVE GEOTROPISM 



No specific difference as regards their responses, between shoot and root — 

 Darwinian curvature — Localisation of geotropic sensibility at the root- 

 tip — Experiments as to whether amputation of root-tip abolishes 

 excitability — The tip of the root the organ of gravi- perception — The 

 perceptive versus the responding organ — True perceptive region . . 536 



CHAPTER XL 



ON CHEMO-TROPISM AND GALVANO-TROPISM 



General difficulties of the investigation — How to overcome these difficulties — 

 Three distinct methods of testing results : ( I ) by variation of longitudinal 



