;8 4 



PLANT RESPONSE 



normal suctional rate will be somewhat reduced. This is 

 seen in the accompanying record (fig. 163), which I obtained 

 with a cut branch of Croton. The normal rate of suction 

 was in this case twenty-six cubic mm. per minute. After the 

 application of potassium nitrate solution this was found 

 to be reduced to seventeen cubic mm. per minute. But if, 

 instead of this, we apply strong solution of sodium chloride, 

 two antagonistic effects will be produced. One, due to 



FlG. 163. Effect of Strong 

 KNO, Solution 



The first record shows the nor- 

 mal and the second the de- 

 pressed rate of suction caused 

 by the reagent. 



FlG. 164. Effect of Strong NaCl 

 Solution 



The first record shows the nor- 

 mal and the second the ex- 

 alted rate of suction caused 

 by the reagent. 



osmotic action, will oppose suction ; and the other, due 

 to the excitatory nature of the reagent, will accelerate 

 suction. The resultant effect will, then, be modified by the 

 excitability of the experimental plant itself. In some cases 

 we should expect to find the excitatory reaction predomi- 

 nant, and in others the osmotic. In repeating the experi- 

 ment, on different specimens of Croton, I have found these 

 theoretical inferences to be fully verified. As the more 

 interesting of the two cases, I give a record (fig. 164) in 



