Page:Researches on Irritability of Plants.djvu/44

Rh obtaining response of Mimosa is shown in the accompanying illustration (fig. 4).

Having thus given an account, in some detail, of the practical working of the Resonant Recorder, it will now be well to show a pair of curves which demonstrate, in a marked manner, the advantage of intermittent over continuous contact in the making of these records (fig. 5). These represent two successive experiments on the same leaf, under identical stimulation of an electrical shock. The recording-plate was here moving at a moderately high speed. The lower record was taken with continuous contact, and the upper with the same recorder but in a state of vibration, giving intermittent contact. The vibration-frequency was 10 times per second. Stimulus was applied at the point marked by the vertical line. A comparison of the two records will show that owing to the relative loss of freedom, due to friction, in the continuous contact, the latent period, or the interval between stimulus and initiation of response, is prolonged and the amplitude of the response itself reduced. In the case of the intermittent contact, on the other hand, we see that besides the freedom from this particular error we have the further advantage that the record itself contains its own time-marks, the successive dots being at intervals of one-tenth of a second.

We have next to consider the practicability of devising,