PLANT RESPONSE 49 



(fig. 27) under strong stimulation. I was able in some 

 cases to trace this process of gradual reversal, by 

 continuously increasing the intensity of stimulus. It 

 was then found that as the stimulus was increased, the 

 positive at a certain point underwent a reversal into 

 the normal negative response (fig. 28). 



The plant thus gives a reversed response under 

 abnormal conditions of staleness. I have sometimes 



FIG. 28. ABNORMAL POSITIVE PASSING INTO NORMAL NEGATIVE IN A STALE 

 SPECIMEN OF LEAF-STALK OF CAULIFLOWER 



Stimulus was gradually increased from 1 to 10, by means of spring-tapper. When 

 the stimulus intensity was 10, the response became reversed into normal 

 negative. (Parts of 8 and 9 are out of the plate.) 



found similar reversal of response when the plant is 

 subjected to the abnormal conditions of excessively 

 high or low temperature. 



Radial E.M. variation. We have seen that a current 

 of response flows in the plant from the relatively more 

 to the relatively less excited. A theoretically important 

 experiment is the following: A thick stem of plant 

 stalk was taken and a hole bored so as to make one 

 contact with the interior of the tissue, the other being 



E 



