288 RESEARCHES ON IRRITABILITY OF PLANTS 



plant may become so excessive as to manifest itself by 

 outward response, apparently automatic. 



Thus I have obtained from Biophytum seemingly auto- 

 matic pulsation by subjecting a vigorous plant to the 

 favourable conditions of light and warmth. In a particular 

 case the favourable temperature was found to be 35 C. 

 When this was lowered to 29 C. the pulsations came to 

 a stop. 



It is thus clearly seen that there is no strict line of demar- 

 cation between multiple and automatic responses so called. 

 An ordinarily responding plant like Biophytum, which gives a 

 single response to a single moderate stimulus, and multiple 

 responses to a strong stimulus, will in very favourable circum- 

 stances, that is to say, when it has absorbed an excess of 

 energy from without, become automatically responding. 



Conversely, an automatically responding plant in un- 

 favourable circumstances is found to be converted to the 

 condition of an ordinarily responding plant. The leaflet 

 of Desmodium gyrans under favourable conditions is found 

 to execute pulsatory movements which appear to be spon- 

 taneous. But when this plant is subjected to unfavourable 

 conditions, then its spontaneous rhythmic activity comes 

 to a stop. In this condition of standstill, the reaction of the 

 leaflet is like that of Biophytum. It then gives rise to a 

 single response to a single moderate stimulus, and multiple 

 responses to a strong stimulus. 



There is thus seen a continuity in the multiple and auto- 

 matic responses. Biophytum is equivalent to Desmodium 

 when brought to a state of standstill by depletion of storage 

 of energy. Pulsating leaflets of Desmodium may, on the 

 other hand, be regarded as equivalent to Biophytum with 

 an overflow of energy. 



Summary 



In plant a single moderate stimulus is found to give rise 

 to a single electric response. A strong stimulus, on the 



