522 



PLANT RESPONSE 



in case (a). These different phases of the effect induced by 

 long-continued application of strong stimulus at A — namely 

 the relative negativity of A, followed by neutralisation, 

 followed by reversal or relative negativity of B — are well 

 seen in the record given in fig. 218. Translated into terms 

 of the resulting mechanical response, this would mean : (1) a 

 movement of the organ towards the stimulus ; (2) neutralisa- 

 tion of this movement ; and (3) a pronounced movement 

 away. I give here a tabular statement which shows at a 

 glance the various electrical effects and the corresponding 

 mechanical responses which are theoretically to be inferred 

 from them, the experimental verification of these inferences 

 being given in the next chapter. 



Tabular Statement of Electrical Effects and Inferred 

 Mechanical Responses 



Stimulation 



Electrical and turgidity effects 

 in the responding region 



Mechanical response 

 theoretically inferred 



I. Unilateral, of tip, on Positive electrical and j Convexity of A, and 

 side A : positive turgidity vari- j movement of tip away 



(a) Moderate stimulus. ation of same side A. from stimulus. 



(b) Stronger stimulus. 



[c) Very strong and long- 

 continued stimulus. 



Positive and subsequent 

 negative effects neu- 

 tralise each other. 



No resultant effect. 



Positive twitch, followed 

 by strong negative elec- 

 trical and turgidity 

 variations, of same 

 side, A. 



2. Direct action of 

 stimulus on respond- 

 ing region : 



(a) Moderate stimulus. 



(/>) Stronger stimulus. 



(c) Very strong and long- 

 continued stimulus. 



Negative variation of side 

 acted upon, and posi- 

 tive variation of dia- 

 metrically opposite 

 side. 



Transient twitch away 

 from, followed by 

 strong movement to- 

 wards, stimulus. 



Concavity of the excited, 



with convexity of the 



opposite side. 

 Responsive movement of 



organ towards source 



of stimulus. 



Positive and subsequent 

 negative effects neu- 

 tralise each other. 



Positive twitch, followed 

 by strong negative 

 electrical and turgidity 

 variations of the op- 

 posite side, B. 



No resultant effect. 



Resultant mechanical 

 response opposite to 

 that in 2 (a) ; i.e. 

 movement away from j 

 the stimulus. 



