TIME-RELATIONS OF RESPONSE 51 



rapid at the beginning and very slow towards the end. 

 The maximum rate of recovery was "09 mm. per second in 

 contrast with the maximum rate of contraction of 24 mm. 

 per second. The movement of recovery was about three 

 hundred times slower than the movement of excitatory 

 contraction. 



A stronger stimulus, generally speaking, requires a longer 

 period for recovery. 



Under the physiological depression induced by winter 

 the responsive reactions are modified. The latent period 

 is prolonged and amplitude of response reduced. The 

 period of recovery may also become protracted. 



Different plants exhibit different characteristics of 

 response. Biophytum sensitivum may be taken as a type 

 of quickly reacting plant, while Neptunia oleracea is very 

 sluggish in its reactions. In Biophytum the apex time 

 is reached in a second and the recovery accomplished in 

 3 minutes. In Neptunia the apex time is reached in 180 

 seconds, and recovery completed in 60 minutes. 



Mechanical response of Mimosa is due to differential 

 contraction of the upper and lower halves of pulvinus. 



Erectile responses of Mimosa may be obtained by local 

 stimulation of the upper half of pulvinus. 



Distinction of plants into sensitive and ordinary is 

 arbitrary. Under suitable conditions, ordinary plants, so- 

 called, may be made to exhibit motile response. 



By means of electric response it may be shown that 

 every plant, and every organ of the plant, is sensitive and 

 responds to stimulation by a definite electric change. 



The sensitiveness of Mimosa to electrical stimulus is 

 high and may even exceed that of a human subject. 



