PLANT RESPONSE 



the gradual waning of pulsation, culminating in arrest at 

 the moment of death (fig. 2). Similarly, changes of heat 



and cold, and the influence of 

 various drugs (fig. 3), are all 

 discernible from the modifica- 

 tions which they induce in 

 the pulse-record. 



For the purpose of studying 

 the actions by which the plant 

 responds to the various stimuli 

 of its environment, I have been 

 able to devise apparatus, by 

 means of which records of its 

 responsive pulsations may be 

 made. In the matter of automatic pulsations, we have in 

 plants many instances which have not hitherto been recog- 

 nised ; but in one case which is well known, that of Desmodium 

 gyrans — Hedysarum gyrans, the telegraph-plant — we observe 

 pulsatory movements of its lateral leaflets, which, as I shall 



Fig. 2. Effect of Muscarin in arrest- 

 ing Pulsation of Frog's Ventricle 

 (Gushing) 



The arrow indicates the moment of 

 application of reagent in this and 

 following. 



Fig. 3. Record of Human Pulse 

 (a) before and {l>) after Inhalation of Nitrite of Amyl. (Broadbent.) 



elsewhere show, exhibit a resemblance to those of the animal 

 heart, a resemblance which is not merely superficial, but is 

 the result of causes fundamentally the same. 



This telegraph-plant grows wild on the Gangctic plain, 

 where its Indian name is Bon Cliaral or 'outcast of the 

 forests,' and where the peasant belief is that it dances to the 

 clapping of the hand. It is a papilionaceous plant with 

 trifoliate leaves, of which the terminal leaflet is large, and the 

 two lateral very small. Each of the latter is inserted on the 

 petiole by means of a motile organ known as a pulvinus. 



