MULTIPLE RESPONSE 283 



Mimosa, that when a second stimulus succeeds a first, after 

 an interval of less than one minute, it produces no responsive 

 effect. If, then, a second wave of excitation arrives within 

 the refractory period of the first, we must expect that it will 

 remain mechanically ineffective. In the multiple electro- 

 tactile responses seen in fig. 114, these successive excitations 

 are seen to have occurred at intervals of one minute, com- 

 plete recovery being accomplished in that time. In the 



Fig. 116. Multiple Mechanical Response of Biophytum, due to a Single 

 Thermal Stimulus 



stem, then, the period of recovery is very much shorter than 

 in the pulvinus, and the same waves of excitation which 

 at intervals of one minute produce response in the one 

 case, prove ineffective in the other. Had these periodic 

 waves of multiple excitation been three or four times as 

 slow as they are, we might have been able to observe 

 multiple mechanical responses of the leaf of Mimosa. In 

 connection with this, I may state that I once observed 

 a second mechanical response to a single strong stimulus 



