386 PLANT RESPONSE 



suction, until the whole plant is killed. And from the 

 Shoshungraphic records we find that the final arrest occurs 

 after an appropriately long period. 



In this connection, I shall describe some very interesting 

 results of rapid arrest of suction, which I have often obtained 

 by the action of poison. I was already familiar with a fact 

 which I had come across while studying the effects of various 

 chemical reagents on the longitudinal response of radial 

 organs namely, that death was attended in such cases either 

 by an abnormal contraction or by an abnormal relaxation. 

 These two effects were liable, again, to be modified by the 



Fig. 165. Effect of Copper Sulphate Solution 



The first part of the record shows the normal rate 01 suction. The asterisk 

 denotes the time of application of the poisonous reagent. 



tonic condition of the tissue. In now studying the effect 

 of solution of copper sulphate on the suctional activity of 

 Croton, I noticed certain peculiarities in the record, which 

 appeared to be related to the results just described. These 

 peculiarities, it should be mentioned, were specially notice- 

 able in those specimens which were experimented on during 

 the month of April, that is to say, at the end of the Indian 

 spring. 



In a particular experiment the normal suctional rate 

 had been fifteen cubic mm. per minute. On the application 

 of copper sulphate, the suctional movement was quickly 



