CONTENTS XV11 



cold— (r) by fatigue — Variation of conductivity : (a) by cold — (/>) by 

 rise of temperature — (c) by fatigue — (d) by anaesthetics — -Variation of 

 receptive excitability by ether -Conductivity versus excitability — 

 Abolition of motile excitability without abolition of conductivity — • 

 Hydro-mechanical theory of transmission of stimulus untenable . .216 



CHAPTER XIX 



ON ELECTROTONUS 



The anode acts as a block to the transmission of stimulus — Opposite effect 

 of kathode — Experiments on Biopkytum, showing variations of con- 

 ductivity by anode and kathode respectively — Experiments on Mimosa, 

 showing increase of motile excitability at or near the kathode, and 

 diminution of motile excitability at or near the anode - Curious ' develop- 

 ment ' of response, near the kathode . . . . . . .231 



CHAPTER XX 



ON THE VELOCITY OF TRANSMISSION OF EXCITATORY WAVES 

 IN PLANTS 



Difficulties in accurate determination of velocity of transmission, due to 

 unknown variations of excitability arising from injury, and variations of 

 conductivity through fatigue — A perfect method of obtaining accurate 

 and consistent results — Relative advantages of studying conduction in 

 plants as compared with animals — Determinations of velocity of trans- 

 mission in centripetal and centrifugal directions — Preferential conductivity 

 in centrifugal direction — Diminution of conductivity and excitability by 

 fatigue — Within a certain critical interval, organ ' refractory ' to further 

 stimulus — Increased velocity of transmission with increasing stimulus — 

 Measurement of diminution of conductivity by cold — Fibro-vascular 

 elements the best conducting channels — Conductivity lengthwise greater 

 than crosswise — Electric mode of determination of velocity of trans- 

 mission — Indifferent parenchymatous tissues practically not transmitters 

 of excitation — Comparative tables showing velocity of transmission in 

 various plant and animal tissues ........ 238 



CHAPTER XXI 



ON DETECTION OF EXCITATORY PULSE DURING TRANSIT L'Y 

 ELECTROTACTILE AND ELECTROMOTIVE METHODS 



Pfeffer's experiment on expulsion of water from excited cells — Author's 

 experiment on a delicate method of detecting excitatory expulsion of cell- 

 sap — Chemical method of determining velocity of transmission of excita- 

 tion — Electrotactile detector — Demonstration of passage of excitatory 



a 



