192 LIFE AND WORK OF SIR JAGADIS C. ROSE 



stimulus acts indirectly in the root. Bose had shown that 

 the effects of direct and indirect stimulus on growth are 

 antithetic ; it therefore follows that the responses 'of shoot 

 and root to the direct and indirect stimulus must be of 

 opposite signs. 



Bose went further and carried out direct experiments 

 on the characteristic responses of the root. He applied 

 various forms of stimuli, first directly on the responding 

 growing region of the root, and found that the induced 

 curvature was "towards the stimulus; he next applied the 

 same stimuli on one side of the root-tip, and the response 

 was by movement away from the stimulus. His generalisation 

 that direct stimulus and indirect stimulus induce opposite 

 responsive movements became verified even in the case 

 of roots. 



Objections had been raised about Darwin's experiment 

 on the decapitation of roots abolishing geotropic response ; 

 it was urged that the shock of operation might of itself 

 abolish all sensibility. In order to meet this objection 

 Bose carried out his electric experiments on the reaction 

 of different zones of intact root under the stimulus of 

 gravity. When he made his electric contact at one side 

 of the root-tip, displacement of the root from vertical to 

 horizontal position at once gave the negative electric response, 

 showing that the root-tip had become directly stimulated. 

 Restoration of the root to the vertical position was followed 

 by disappearance of all signs of irritation. He next applied 

 his electric contact at the responding growing region of the 

 root, which on displacement from a vertical to a horizontal 

 position gave rise to positive electric response, which is the 

 indication of indirect effect of stimulus. By this crucial 

 experiment carried out on an intact plant Bose was able 

 to establish an underlying unity even in responses which 

 appeared to be so diametrically opposite. 



