Page:Researches on Irritability of Plants.djvu/76

Rh signal. So long as the current is flowing, the writer remains in the up-position and draws a horizontal line (fig. 20). At the time of make it will be noticed that, owing to inertia, the writer was momentarily jerked somewhat above the level of this up-position. This jerked line, therefore, always marks the moment of make, and the horizontal line at the higher level the continuation of the current. When the current is broken, the writer falls suddenly to its original level. Thus a jerked up-line indicates the moment of the application of the make-shock,

Rh

and the down-line the application of the break~shock. In the two accompanying figures are given records of the effects of make- and break-shocks.

In the record (fig. 20) the secondary coil was placed at the reading of ·75 unit. It will be noticed that at 'make' there was no response. But there was response at 'break,' which took place ·1 second later, the delay being due to the latent period. In the next experiment, with the same plant, the coil was pushed into the reading of 1. It will be seen (fig. 21) that excitation was here effective at 'make,'