Page:Researches on Irritability of Plants.djvu/84

Rh the series taken. It should be mentioned that in all these cases the stimulus employed was of constant intensity—namely, 2.

In fig. 27 are shown the responsive effects of an identical stimulus at these three different temperatures. At 22° C. it is seen that the height of response is small and the recovery extremely prolonged. At 27° C. we find the amplitude of response enhanced and the rate of recovery increased. At

32° C. the height of response is still more enhanced and the rate:of recovery, as seen in the steepness curve, still further increased. In fig. 28 is given another set of records taken on a faster-moving plate, exhibiting the effect of temperature on the amplitude of response. It will be shown in a succeeding chapter that the latent period also is affected, being progressively decreased with rising temperature.

It is usually supposed that in Mimosa every effective stimulus causes the maximum response. That this is not the case comes out very clearly in careful records taken