174 Professor Jagadis Ch under Bose [May 2'.), 



Thus, when au animal is struck hj a blow, it does not respond at 

 once. A certain short interval elapses between the incidence of the 

 blow and the beginning of the reply. This lost time is known as 

 the latent period. In the plant is there any definite period which 

 ela])ses between the incident blow and the responsive twitch ? Does 

 this latent period undersro any variation as in the animal, with 

 external conditions ? Is it possible to make the plant itself write 

 down this excessively minute time-interval ? 



Next, is the plaiit excited by various irritants which also excite 

 the animal ? If so, at what rate does the excitatory impulse travel 

 in the ])lant r Under what favourable circumstances is this rate of 

 transmission enhanced, and under what other circumstances is it 

 retarded or arrested ? Is it possible to make the plant itself record 

 this rate and its variation ? Is there any resemblance between the 

 nervous impulse in the animal and the excitatory impulse in the 

 plant ? 



The characteristic effects of various drugs are well known in the 

 case of the animal. Is the plant similarly susceptible to their action ? 

 AVill the effect of poison change with the dose ? Is it possible to 

 counteract the effect of one poison by means of another ? 



In the animal there are certain automatically pulsating tissues 

 like the heart. Are there any such spontaneously beating tissues in 

 the plant ? If so, are the pulsations in the animal and the plant 

 affected by external conditions in a similar manner ? What is the 

 real meaning of spontaneity ? 



CJrowth furnishes us with another example of automatism. The 

 rate of growth in a plant is far below anything we can directly 

 perceive. How, then, is this growth to be magnified so as to be 

 rendered instantly measurable ? What are the variations in this 

 infinitesimal growth under external stimulus of light and shock of 

 electric current ? What changes are induced by giving or with- 

 holding food ? What are the conditions which stimulate or retard 

 growth ? 



And, lastly, when by the blow of death life itself is finally 

 extinguished, will it be possible to detect the critical moment ? 

 And does the plant then exert itself to make one overwhelming 

 reply, after which response ceases altogether ? 



Plant-Script. 



We shall first take up the question of recording response of a 

 l|lant like Mimosa. Here, at the joint of the leaf, there is a cushion- 

 like mass of tissue known as the pulvinus. This serves as the motile 

 apparatus. The swollen mass on the lower side is very conspicuous. 

 Under excitation, the parenchyma in this more effective lower half 



