374 COMPARATIVE ELECTRO-PHYSIOLOGY 



absorbed, by some process of accommodation. I have shown 

 elsewhere 1 that the effect of poison on the response of 

 growth is modified to a remarkable extent by the different 

 tonic conditions of the tissue. The experiments in question 

 were carried out on similar specimens of Crinum lily, in 

 which the only difference induced depended on the fact that 

 one set had been kept at a temperature of 30 C, and were 

 thus in moderate tonic condition, while the others had been 

 maintained at 34 C., bringing about, as I have shown, an 

 optimum tonic condition. The application of a 5 per cent, 

 solution of copper sulphate to one of the first of these was 

 found to induce the rapid decline and final arrest of growth, 

 while a similar application, on a specimen in the optimum 

 condition of the second set, induced a preliminary exaltation 

 followed by a slow depression and ultimate arrest of growth, 

 the last-named, however, being reached only after the lapse 

 of a considerable time. 



The difference of effect under different tonic conditions 

 was still more strikingly exhibited by the application of a 

 smaller dose namely, of a I per cent, solution. This was 

 found to induce a depression of growth, which was ultimately 

 fatal to the plant, in the case of specimens kept at 30 C. 

 But when the same dose was applied to a plant which had 

 been kept at 34 C., the effect was seen in a marked 

 exaltation of the rate, for a fairly long time, after which it 

 shook off the effect of poison altogether, resuming its normal 

 rate of growth. 



Thus the effect of poison on the various activities of the 

 plant is seen to depend not only on the amount of the 

 agent, and the duration of application, but also on the 

 tonic condition of the tissue. Strong and prolonged applica- 

 tions will abolish all active processes, by inducing the death 

 of the plant. In accordance with this, I find that in certain 

 plants under the action of copper sulphate the arrest of 

 suction is more rapid than in others. All alike, however, 

 exhibit permanent arrest sooner or later. 



1 Bose, Plant Response, pp. 487-488. 



