PLANT RESPONSE 



4 1 



photographic record of fatigue in the leaf-stalk of 

 cauliflower. 



It is evident that residual strain, other things being- 

 equal, will be greater if the stimuli have 

 been excessive. This is well seen in 

 fig. 23, where the set of first three 

 curves A is for stimulus intensity of 45 

 vibration, and the second set B, with an 

 augmented response, for stimulus in- 

 tensity of 90 vibration. On reverting 

 in c to stimulus intensity of 45, the 

 responses are seen to have under- 

 gone a great diminution as compared 

 with the first set A. Here is seen 

 marked fatigue, the result of overstrain from excessive 

 stimulation. 



If this fatigue be really due to residual strain effect, 

 then, as strain disappears with time, we may expect the 



Fm. 22. FATIGUE 

 IN LEAF-STALK OF 

 CAULIFLOWER 



Stimulus : 30 vibration 

 at intervals of one 

 minute. 



4-5 



4-5 



ABC 

 FIG. 23. EFFECT OF OVERSTRAIN IN PRODUCING FATIGUE 



Successive stimuli applied at intervals of one minute. The intensity of 

 stimulus in C is the same as that of A, but response is feebler owing to 

 previous over-stimulation. Fatigue is to a great extent removed after 

 fifteen minutes' rest, and the responses in D are stronger than those in C. 

 The vertical line between arrows represents '05 volt. (Turnip leaf-stalk.) 



responses to regain their former height after a period 

 of rest. In order to verify this, therefore, I renewed the 

 stimulation (at intensity 45) after fifteen minutes. It 



