xiv RESEARCHES ON IRRITABILITY OF PLANTS 

 CHAPTER XI 



VELOCITY OF TRANSMITTED IMPULSE IN PLANTS 



PAGE 



Detection of transmitted excitation by means of electromotive 

 variation — Specific tissue for conduction of excitation — Hydro- 

 mechanical theory of transmission of stimulus — Propagation of 

 excitatory protoplasmic change — Physiological test — Auto- 

 matic record of transmission-period — Conditions for obtaining 

 constant velocity — Determination of velocity of transmission 

 in Mimosa — Differential method of determining velocity — 

 Constancy of results — Tabular statement of different deter- 

 minations of velocity — Effect of intensity of stimulus on 

 velocity of transmission — Effects on sub-tonic tissue and on 

 tissue in optimum condition — After-effect of stimulus in 

 enhancing conductivity — Effect of optimum condition — 

 Disturbing action of leakage of exciting current — Effect of 

 fatigue — Effect of temperature — Velocity of transmission in 

 Biophytum and Averrhoa — Direction of preferential conduction 132 



CHAPTER XII 



EXCITATORY CHARACTER OF TRANSMITTED 

 IMPULSE IN PLANTS 



The hydro-mechanical theory — Inconclusive character of the 

 anaesthetic experiment of Pfeffer and scalding experiment of 

 Haberlandt — Kiihne's experiment showing transmission of 

 excitation under intense stimulation in a rigored nerve — 

 Error introduced by employment of excessive intensities of 

 stimulus — Discriminative polar effect of current in excitation 

 — Block of transmission of excitation by local application of 

 cold — Restoration of normal conductivity by tetanising shock 

 in tissue paralysed by cold — Electro tonic arrest of excitatory 

 impulse — Action of various poisons in inducing block of con- 

 duction .......... 154 



CHAPTER XIII 



THE POSITIVE RESPONSE 



Two opposite kinds of responses, negative and positive — Excitatory 

 contraction, negative turgidity variation, fall of leaf, and 

 concomitant negative electric variation — Positive electric 

 response — Positive or erectile mechanical response — Dual 

 impulses under different forms of stimuli — Exhibition of 

 positive and negative impulses by different plants — Con- 

 ditions for obtaining positive response — Characteristics of 

 positive impulse — Masking and unmasking of positive effect — 

 Laws of Direct and Indirect effects of stimulus . . . 176 



