Page:Researches on Irritability of Plants.djvu/95

72 slows down, and the leaf becomes for a time stationary at the apex. These varying rates of fall are seen in the growing and then in the diminishing intervals between the dots.

If instead of giving the full period of rest necessary for complete protoplasmic recovery, the period of rest be

shortened, we obtain a diminution in the height of response indicative of fatigue. This is well seen in fig. 34. The first three uniform responses here—taken, as it is unnecessary to repeat, under uniform stimulation—were recorded at intervals of 15 minutes each. The intervals between successive stimulations were now shortened to 10 minutes, which at once results in a fatigue-diminution of the height of responses. The second three responses appear crowded together, owing to the shortening of the time allowed for record. The time of recovery, after the third of these responses, was again restored to its first value of 15 minutes, and we see at once the reversion of the response to its original height. A similar exhibition of fatigue is also seen