Page:Researches on Irritability of Plants.djvu/147

124 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 .1 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

is seen that the latent periods obtained from the two experiments are the same—namely, .08 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 employed 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