338 RESEARCHES ON IRRITABILITY OF PLANTS 



blown away and fresh air substituted in the chamber. But 

 the arrest persisted for half an hour. After this interval 

 there was a revival, and the pulsation attained for a time 

 an amplitude even greater than the normal. 



Effect of Carbon Disulphide 



The vapour of this reagent also arrests the pulsating 

 activity of the leaflet. The record (fig. 184) shows the 

 quick arrest after a single pulsation. Substitution of fresh 

 air is seen again to revive the pulsation. 



Effect of Copper Sulphate Solution 



As an example of toxic agents we may take solutions of 

 substances like copper sulphate. When a strong solution of 



Fig. 185. — Effect of internal application of CuS0 4 solution 

 in inducing arrest of pulsation. 



this substance is applied directly on the pulvinule, an arrest 

 takes place within a short time. The effect is delayed when 

 the solution is applied at the cut end of the petiole. A record 

 of the effect of internal application of copper sulphate 

 solution is given in fig. 185. 



Effect of Potassium Cyanide Solution 



We saw in Chapter XII. that the toxic effect of potassium 

 cyanide in abolishing the conductivity of the tissue was far 



