are practically uniform between the hours of 5 and 6 p.m., a continuous decline is manifested after setting in of darkness (7 p.m.); the fall of excitability continues even after sunrise (6-30 a.m.), response being practically abolished at 8 a.m. The excitability is then gradually restored in a staircase manner, the maximum being reached after 12 noon. After attaining this, the excitability remains more or less constant till the evening. It will be noticed that the amplitude of response at 5 p.m. on the second day was the same as the corresponding response on the previous day.
The results of this and numerous other records taken in spring may be summarized as:—
- The maximum excitability of Mimosa is attained between 1 and 3 p.m., and remains constant for several hours. In connection with the constancy of response at this period, it should be remembered that when the response is at its maximum a slight increase of excitability cannot further enhance the amplitude of response.
- The excitability, generally speaking, undergoes a continuous decline from evening to morning, the response being practically abolished at or about 8 a.m.
- From 8 a.m. to 12 noon, the excitability is gradually enhanced in a staircase manner, till the maximum excitability is reached after 1 p.m.
I have obtained numerous records in support of these conclusions, some of which are reproduced in the following figures. In these cases responses to uniform stimuli at intervals of half an hour were taken at different parts of the day, the recorder employed being of the Resonant type.
