1914] JOLIV ETTE—PILOBOLUS 105 
box, so that the glass plate on which the spores were caught fitted 
closely against the slide containing the openings. The openings 
not desired could be closed by means of two additional slides fitted 
in the groove from either end and outside the slide containing the 
openings. ‘The inside of the box and of the strips was dull black. 
The culture in this series was kept throughout the experiment 
at a distance of 23 cm. from the central point between the two 
openings. The surface of the culture was vertical and faced the 
slide containing the two openings. The exposed surface of the 
culture was 2cm. in diameter. The light entering each of the 
Openings was made to fall upon the exposed surface of the culture. » 
The intensities of the light entering the two openings were equal 
or as nearly so as they could be made by measurement. The follow- 
ing device was followed in order to make the lights as nearly equal 
as possible. A single carbon filament incandescent lamp was placed 
at a distance midway between the two openings. By means of 
two mirrors placed at equal distances and equal angles one on either 
side of the lamp, the light was reflected through the opening to the 
exposed surface of the culture. In order to exclude the light of 
either mirror from the opposite opening a partition was set up in 
front of the box midway between the two openings, exactly similar 
to that used in the set of experiments last described. 
With the change in the distance between the two openings it 
Was necessary to change slightly the angles of the mirrors from the 
light in order that the spot of light reflected from the mirrors 
through the openings would strike the exposed surface of the culture. 
The condition of the experiments thus necessitated a slight change of 
light intensity from experiment to experiment, but the intensities 
of the light passing through the two openings at any one time were 
equal. 
This set of experiments was performed in a dark room in the 
botanical laboratory of Leland Stanford Junior University. 
In the first experiment, when the distance between the centers 
of the two openings was 5 cm., a total number of 38 sporangia 
Were fired on the glass, 10 and 13 striking the left and right openings 
Tespectively. Only 2 of the 15 sporangia which failed to strike the 
opening were outside of the adjacent 1-cm. strips. 
