VELOCITY OF TRANSMITTED IMPULSE 151 



petiole of Biophytum, the average value of which is about 

 2 mm. per second. Fig. 89 shows a record obtained with 

 a typical specimen. Stimulus was applied at a distance 

 of 50 mm. from the responding leaflet. The record was 

 taken by means of the Oscillating Recorder, the successive 

 dots being at an interval of a second. It will be seen 

 that the response took place 24-5 seconds after the appli- 

 cation of stimulus. Making allowance for the latent 

 period, the average value of which in Biophytum is 



Fig. 89. — Record giving transmission-time in Biophytum : 

 Successive dots at intervals of a second. 



•4 second, the velocity of transmission in this particular 

 case is 2 - i mm. per second. The velocity in the petiole of 

 Averrhoa carambola varies from -5 to 1 mm. per second. 



Direction of Preferential Conduction 



In connection with the determination of velocity of 

 transmission of excitation in Biophytum, I made the discovery 

 of the curious phenomenon of preferential conductivity. 

 It was found that the state of excitation travelled through 

 the conducting petiole of Biophytum with greater facility 

 in one direction than in the opposite. The experiment 

 was carried out by employing a leaflet, situated midway 

 in the petiole, as the motile indicator. Equal stimuli were 



