INQUIRY INTO CAUSES OF AUTONOMOUS MOVEMENTS 303 



of autonomic pulsations may be obtained in Biophytum under 

 the continuous stimulation of light. The recovery not being 

 complete after each pulse, the result is a progressive folding 

 downwards of the leaflets, and this makes it impossible after 

 a time to observe further responses. I shall presently describe, 

 however, another method of supplying the plant with energy, 

 by thermal means, in which case 

 the autonomous pulsation in Bio- 

 phytum is prolonged indefinitely. 



{c) On Desmodiuni leaflet at 

 standstill. — Turning now to the 

 leaflet of Desmodiuni in a state of 

 standstill, I find that application 

 of sunlight initiates rhythmic move- 

 ments. In a particular experiment, 

 h"ght was continuously applied for 

 half an hour, and there were pro- 

 duced in that time seven vibrations. 

 The responses were found to under- 

 go 'staircase' increase by increas- 

 ing absorption of energy, and the 

 resultant increase of molecular 

 mobility produced in the tissue. On the stoppage of light 

 the rhythmic pulsations persisted for some time, the ampli- 

 tude, however, undergoing diminution owing to the run-down 

 of absorbed energy. 



4. Thermal : (a) Induction of autonomous response 

 in Biophytum. — I shall now describe an experiment of very 

 great theoretical importance, by which I have able to convert 

 a specimen of Biophytum from an ordinarily into an auto- 

 matically responding plant. Guided by the theoretical in- 

 ference which I have already stated, that it is an excess of 

 energy that brings about the condition of automatism, I 

 subjected a specimen of Biophytum to the constant stimulus 

 of a moderately high temperature. I first placed the speci- 

 men in a chamber whose temperature was 37° C, and it was 

 astonishing to see the younger (and therefore more excitable) 



Fig. 123. Multiple Response 

 of Biophytum under the 

 Continuous Action of Light 



