56 GERMINATION 



of " stimulus " we substitute the word " irritation," we 

 can better understand what happened. 



In Chapter II. I have stated that the efiFect of electrical 

 stimulation continues after disconnection of current and 

 this statement deserves attention for it has a direct bearing 

 upon karyokinesis and upon the possible production of 

 cancer in vegetables, as we shall see when we come to the 

 study upon the subject. 



Writing of excitations induced by light, Bose says that 

 " energy may find outward expression, even after the cessa- 

 tion of the stimulus." An example of this was seen in the 

 mechanical response of a Desmodium leaflet. " The plant 

 was at first in a sub-tonic condition, and the autonomous 

 pulsation of its lateral leaflets had come to a standstill. 

 One of these was now exposed to the continuous action of 

 light and its record taken. . . . Under this stimulus 

 of light, multiple responses were initiated, which persisted 

 for a time as an after-effect, even on the cessation of light." 

 In taking electrical records of the after-effect of stimulation 

 by light he obtained similar mutiple after-effects. 



He expresses the opinion that " a plant or an animal is 

 an accumulator which is constantly storing up energy from 

 external sources, and numerous manifestations of life — 

 often periodic in their character — are but responsive expres- 

 sions of energy which have been derived from external 

 sources and is held latent in the tissue." 



That reminds me of Dr. Keith Lucas' theory of the 

 conduction of the nervous impulse. He said : *' . . . that 

 the nervous impulse depends for its transmission ^n the 

 supply of energy by the nerve along its course. If this view 

 is correct we may be justified in supposing that by its very 

 nature the nervous impulse is dependent for its intensity 

 only on the conditions which it encounters during conduc- 

 tion and not on the intensity with which it is initiated." 



As well imagine a flow of water without any difference 

 of level, or a current, too weak to actuate the instrument 

 at the other end, setting out upon its passage through an 

 Atlantic cable, dependent upon the kindness of an earth- 

 current to help it along. 



