Page:Researches on Irritability of Plants.djvu/86

Rh being very slight. After the seventh, it was found that the responses did not undergo any further increase.

The range within which the increasing effect is seen is relatively extended in the case of plants in a somewhat sub-tonic condition. But when the specimen is highly excitable the range of variation is proportionately restricted.

The break-shock is more effective in inducing excitation than the make-shock.

Stimulus, singly ineffective, becomes effective on repetition. The effective stimulation is equal to the individual intensity of stimulus multiplied by the number of repetitions.

The effect of load on the response of Mimosa is similar to that on the contractile response of muscle. With increasing load the height of response undergoes a progressive diminution With shortening of period of recovery.

Within limits, the amount of work performed by a muscle increases with the load. The same is true of work performed by the pulvinus of Mimosa.

In a given case the rate of work performed by the pulvinus of Mimosa was 7480 mm. mgrms. per second.

The effect of rising temperature on response is to enhance the amplitude and to shorten the period of recovery.

In Mimosa, increasing intensity of stimulus induces increasing amplitude of response. This, however, soon reaches a limit.