140 RESEARCHES ON IRRITABILITY OF PLANTS 



another set of records from a different specimen (fig. 84) 

 from which the velocity of transmission is to be determined 

 by the Differential Method. In this case a new recorder 

 was taken, with a vibration-frequency of 20 times per 

 second. Hence the distance between any two successive 

 dots represents a time-interval of one-twentieth of a second. 

 The stimulus intensity was again 3. The lowest record 

 gives us the result obtained when the point of application 

 of stimulus was 30 mm. away from the responding pulvinus. 

 The total time T is here seen to be 2*9 seconds. The 

 next record gives us the result when the point of stimulation 

 was at a distance of 20 mm., and the total time Ti is i'985 



Fig. 84. — Determination of velocity by differential method. Uniform 

 stimuli applied at distances of 30 mm., 20 mm., and directly. Recorder 

 20D.V. 



second. The third and highest gives the record of direct 

 stimulation, the latent period being shown as '085 second. 

 Thus 



Vi = ^ ^ — =107 mm. per second 



2'9 — -085 ^ ^ 



V2 = — Fi TT- = 10' 53 mm. per second 



1.985 - -085 ^^ ^ 



V3 = ^r— = lO'Q mm. per second 



2*9 - 1-985 



It is thus seen that, taking the precautions described, 

 successive determinations of the velocity of transmission 



