Page:Collected Physical Papers.djvu/331

Rh the responses are found to be completely abolished. As all the external conditions were the same in the two series of experiment, the only difference being that in one the stalk was alive, and in the other killed, we have here a further and conclusive proof of the physiological character of electric response in plants.

The same facts may be demonstrated in a still more striking manner by first obtaining two similar but opposite responses in a fresh stalk at A and B, and then killing one half, say B, by immersing that half in hot water. The stalk is replaced in the apparatus; repetition of the experiment shows that whereas the A half gives strong response, the end B gives none.

Uniform responses may be obtained with certain plants in a vigorous condition, and when sufficient period of rest is allowed for complete recovery. The record given below shows the remarkable uniformity of response given by radish. The response of plant is by the induced galvanometric negativity of the excited tissue just as in the tissue of the animal.

The responses however exhibit fatigue by shortening the intervening period of rest. The first four responses