CHAPTER XXIII 



ON MULTIPLE RESPONSE 



Multiple electromotive responses due to a single strong stimulus — Multiple 

 electrotactile responses — Multiple mechanical responses in Biophytum— 

 Cyclic variations in multiple responses — Multiple retinal excitations— Inter- 

 mittent pulse in man and plant — Semi-automatism— Continuity of multiple 

 and automatic response— Conversion of Biophytum into automatically 

 responding plant : conversion of Desmodium into ordinarily responding 

 plant — Similar polar effects of current in Biophytum and in Desmodium 

 leaflet, at standstill —Moderate stimulus in Biophytum and in Desmodium at 

 standstill produces single response ; and strong stimulus, multiple response. 



I HAVE already explained in Chapter III. that the excitatory 

 wave initiated by a stimulus has a concomitant electro- 

 motive wave. If the plant experimented on is provided with 

 motile leaves or leaflets, the excitation is evidenced by the 

 simultaneous mechanical response of the motile organ, and 

 the electrical response of galvanometric negativity. 



Multiple electromotive responses due to single strong 

 stimulus. — In my investigations on electrical response in 

 plants, I was surprised to find that whereas a single mode- 

 rate stimulus gave rise to a single electrical response, a very 

 strong stimulus very often initiated a multiple series of 

 responses. I have obtained such multiple responses to a 

 single stimulus with all kinds of plants, ordinary and ' sensi- 

 tive,' and under the action of various forms of stimulus — 

 chemical, thermal, and mechanical. 



To obtain these multiple electrical responses in an unmis- 

 takable manner it is necessary that the excitation should 

 reach one electrical contact and not the other, for in the latter 

 case there would be complications arising from diphasic 

 variation. The necessary condition may be fulfilled by 



