294 PLANT RESPONSE 



energy has fallen below par, be reduced to the condition of 

 an ordinarily responding plant, giving single response to 

 single moderate stimulus, and multiple response to strong 

 stimulus. 



Summary 



On application of a strong stimulus, of whatever nature, 

 to a vegetable tissue, a multiple series of electromotive re- 

 sponses is produced. These multiple responses may also be 

 observed by the electrotactile method. 



These multiple excitations, in consequence of a single 

 strong stimulus, may be observed in Biophytum as multiple 

 mechanical responses. 



These multiple responses may be uniform in character, or 

 may exhibit cyclic variations, similar to those observed in the 

 rhythmic pulsations of animal tissues. 



As, in the case of a plant-tissue, a strong stimulus causes 

 multiple excitations, so, in the retina, strong stimulus of 

 light causes multiple visual excitations, seen in recurrent after- 

 images, which have the same characteristics as the multiple 

 after-effects of stimulation in Biophytum. 



There is no strict line of demarcation between the 

 phenomena of multiple and of automatic response. Under 

 very favourable circumstances — that is to say, when it has 

 absorbed an excess of energy from without — an ordinarily 

 responding plant like Biophytum will become converted into 

 an apparently automatically responding plant, like Desmodium. 



Conversely, under unfavourable circumstances — that is 

 to say, when the sum total of its energy is below par — an 

 automatically responding plant like Desmodium, will become 

 converted into an ordinarily responding plant like Biophytum. 

 Its leaflets then come to a state of standstill. 



Desmodium leaflets in a state of standstill respond to 

 stimulus in exactly the same way as do those of Biophytum. 

 To moderate stimulus, both give single response ; the polar 

 effects of currents in both are the same ; and strong stimula- 

 tion causes a multiple series of responses in both. 



