124 RESEARCHES ON IRRITABILITY OF PLANTS 



we should find no difference of time as between the two 

 cases ; and this stimulation would be equivalent to direct 

 stimulation and be expected to give us a latent period 

 of the order of *i second. 



I give below (fig. 74) the record of this experiment, 

 which shows that under alternating shocks the excitation is 

 simultaneous, and that the value of the latent period is then 

 independent of the points of application of the electrodes, 

 provided the pulvinus be included in the tract. The upper 

 of the two records was taken when the electrodes were 

 10 mm. and the lower when they were 80 mm. apart. It 



Fig. 74. — Simultaneous excitation in interposed tract under 

 alternating shock. In upper record two electrodes were 

 1 cm. apart, in lower record, 8 cm. apart. 



is seen that the latent periods obtained from the two experi- 

 ments are the same — namely, *o8 second — which is of the 

 order of other determinations already obtained. Had the 

 stimulation not been simultaneous this value would have 

 been increased to at least 3 second or to 2*5 seconds in the 

 respective instances. The identity of results in the two 

 cases shows, moreover, that we are measuring the effect 

 of a constant factor, which is the latent period. 



For the purpose of applying alternating shocks I em- 

 ployed as usual a Ruhmkorff coil. In this the spring 

 vibrator in the primary was so adjusted as to cause 

 100 interruptions per second. This would give in the 

 secondary circuit 200 alternating shocks per second, of 



