172 RESEARCHES ON IRRITABILITY OF PLANTS 



successive dots being 'i second. The total time was there- 

 fore 2 7 seconds. Subtracting from this the latent period 

 •15 second, we obtain 2*5 seconds as the actual time for 

 transmission through 30 mm. The time of transmission 

 through 10 mm. is therefore '83 second. 



Record 2 of the series shows the effect of application 

 of copper sulphate solution for 20 minutes on a por- 

 tion of petiole 10 mm. in breadth. It is noticed that the 

 transmission-time has been prolonged by ten spaces, i.e. 

 by 1 second. Assuming that the effect of poison was 



Fig. 94. — Effect of copper sulphate solution in the retardation and 

 final arrest of conduction : (1) Normal record ; (2) Retardation 

 caused by 20 minutes' application ; (3) Arrest caused by application 

 for 40 minutes ; (4) Record of direct stimulation. 



localised, it is seen that it had during 20 minutes' application 

 delayed transmission through 10 mm. from -83 second to 

 1-83 second. By the absorption of a small quantity of 

 poison the conductivity has thus been reduced by more 

 than 50 per cent. 



Record 3 of the series was taken after a further period 

 of 20 minutes. The transmitted effect is seen to be com- 

 pletely blocked by the application of copper sulphate for 

 40 minutes. In order to show that the absence of response 

 was due not to the abolition of motile excitability of 



