36 RESPONSE IN THE LIVING AND NON-LIVING 



is thrown into a state of complete tetanus, in which it 

 appears to be held rigid. If the rapidity be not suffi- 

 cient for this, we have the jagged curve of incomplete 

 tetanus. If there is not much fatigue, the upper part 



FIG. 16. UNIFORM RESPONSES (RADISH) 



of the tetanic curve is approximately horizontal, but 

 in cases where fatigue sets in quickly, the fact is shown 

 by the rapid decline of the curve. With regard to all 

 these points we find strict parallels in plant response. 



In cases where there is 

 no fatigue, the successive 

 responses are identical (fig. 

 16). With superposition 

 of stimuli we have fusion 



FIG. 17. FUSION or EFFECT OF f effects, analogous tO the 



RAPIDLY SUCCEEDING STIMULI P i /P ~i*\ 



,,. tetanus of muscle (fig. 17). 



(a) m muscle ; (6) m carrot. v to 



And lastly, the influence 



of fatigue in plants is to produce a modification of 

 response-curve exactly similar to that of muscle (see 

 below). One effect of superposition of stimuli may be 

 mentioned here. 



