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DIURNAL VARIATION OF EXCITABILITY

71

after 8 a.m.; the sensitiveness is then gradually enhanced in a staircase manner.

TABLE III—SHOWING THE RELATION BETWEEN HOURS OF THE DAY, TEMPERATURE, AND EXCITABILITY. (SUMMER SPECIMEN.)

Hours
of
day.		 Temperature Amplitude
of
Response.		   Hours
of
day.		 Temperature Amplitude
of
Response.
1 p.m. 38° C. 22 mm.   1 a.m. 26° C. 21.5 mm.
2 „ 38° „ 23 „   2 „ 26° „ 20 „
3 „ 38° „ 24.5 „   3 „ 25.5° „ 18.5 „
4 „ 37° „ 28 „   4 „ 25.5° „ 17 „
5 „ 35.5° „ 29 „   5 „ 25.5° „ 16 „
6 „ 33° „ 27 „   6 „ 26° „ 15 „
7 „ 31° „ 26 „   7 „ 27° „ 14 „
8 „ 30° „ 26 „   8 „ 29° „ 13 „
9 „ 29° „ 25 „   9 „ 30.5° „ 11 „
10 „ 27° „ 24.5 „   10 „ 33° „ 16 „
11 „ 27° „ 24 „   11 „ 35° „ 17 „
12 „ 26.5° „ 22.5 „   12 „ 37° „ 21 „

SUMMARY.

The moto-excitability of Mimosa was gauged every hour of the day and night, by the amplitude of the response to a testing stimulus. This is effected by means of automatic devices which excite the plant periodically by an absolutely constant stimulus, and record the corresponding mechanical response.

From the record thus obtained, it was found that the excitability of the plant is not the same throughout the day, but undergoes a variation characteristically different at different times of the day. In a typical case in spring

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