Notes . 
419 
In the case of the former (the control) it was possible to estimate 
the angle turned through during successive intervals of time, such as 
5, 10, 15, and 20 1 minutes after exposure. It was not possible to 
do this in the case of short-stimulus experiments, as the cells would 
then have received three additional stimuli, so it was necessary to 
terminate an experiment on examining the result after the period of 
darkening. But the course of events could be reconstructed by 
arranging a series of Mesocarpus cells, each of which received the 
same stimulus, and then examining them one by one at successive 
TABLE I. 
Time of 
stimula- 
tion in 
Angle turned through at end of 
Control. 
Angle turned through at end of 
seconds. 
5 min. 
10 min. 
15 min. 
20 min. 
S min. 
10 min. 
15 min. 
20 min. 
10 
25° 
IO° 
50° 
— 
90 ° 
45 
10° 
25° 
30° 
40° 
r 5° 
45° 
85° 
9 °° 
55 
IO° 
25° 
35° 
45° 
20 ° 
50° 
8o° 
90 ° 
60 
8° 
35° 
6i° 
6 3 ? 
15° 
50° 
8o° 
90 ° 
100 
5° 
36 ° 
65° 
86° 
10° 
50° 
75° 
9 °° 
120 
io° 
32 ° 
65 ° 
9°° 
i o° 
55° 
8o° 
9°° 
Illustrating stimulation of vertical plate with diffused light. 
intervals of time. In order to reduce any chance of error which might 
be due to an accidental deviation from the proper normal, each time- 
experiment was repeated three times, and the mean of the observations 
was accepted provided that there was close agreement between the 
results obtained. 
Thus, as it was desired to ascertain what had happened at 5, 10, 
15, and 20 minutes after stimulation, twelve microscopes were arranged 
1 It was found, as the result of many observations, that no further effect was 
produced after the lapse of twenty minutes from the time of stimulation in the 
experiments with diffused light. This does not hold good, however, with the 
observations (Series II) on the effect of strong illumination. 
