RELATION BETWEEN STIMULUS AND RESPONSE 97 



continued progressively, until r with the stimulus-intensity of 

 eight, the time required for restoration to the original con- 

 dition was as much as 4 minutes 40 seconds, or exactly seven 

 times that necessitated by unit-stimulus. 



All these peculiarities are observable in the electrical 

 responses of plants, as will be seen from the record in fig. 48. 

 The stimulus applied was vibrational, and was increased in 

 amplitude in successive experiments, from 2*5° to 7-5° to 

 io° to 1 2-5°. It will be seen that here also as in the case 



Fig. 48. Increased Electrical Response with Increasing Vibrational Stimuli 

 (Cauliflower-stalk) 



Vertical line to right = - i volt. Stimuli applied at intervals of three minutes. 



of the response of skeletal muscle, and the longitudinal 

 response of plants, the amplitude of response increasing with 

 increasing stimulus tends to approach a limit. These curves 

 also show the increase in the period required for complete 

 recovery, but in a manner different from that of fig. 46. In 

 fig. 46 the time-intervals were suitably increased, to allow of 

 complete recovery. In the case of the electrical responses, 

 however, stimuli were applied at equal intervals of time 

 throughout. This was enough to bring about complete 



II 



