Fig. 34.—Responses to Increasing Stimulus obtained with Two Specimens of Stalk of Cauliflower
In (a) fatigue is absent, in (b) it is present.
In one case there is no fatigue, the recovery from each stimulus being complete. Every response in the series therefore starts from a position of perfect equilibrium, and the height of the single responses increases with increasing stimulation. But in the second case, the strain is not completely removed after any single stimulation of the series. That recovery is partial is seen by the gradual shifting of the base line upwards. In the former case the base line is horizontal and represents a condition of complete equilibrium. Now, however, the base line, or line of modified equilibrium, is tilted upwards. Thus even in this case if we measure the heights of successive responses from the line of absolute equilibrium, they will be found to increase with increasing stimulus. Ordinarily, however, we make no allowance for the shifting of the base line, measuring response rather from the place of its previous recovery, or from the point of modified equilibrium. Judged in this way, the responses undergo an apparent diminution.
FOOTNOTES:
[13] See ‘On Electric Touch,’ Proc. Roy. Soc. Aug. 1900.
CHAPTER VIII
PLANT RESPONSE—ON THE INFLUENCE OF TEMPERATURE
- Effect of very low temperature
- —Influence of high temperature
- —Determination of death-point
- —Increased response as after-effect of temperature variation
- —Death of plant and abolition of response by the action of steam.