Allen and Jolivette—Light Reactions of Pilobolus. 571 
the center of the opening. The sporanges falling upon each 
opening are recorded separately. As the distance from the 
culture to the openings is short, very few sporanges fall be¬ 
low the openings. 
At night, when the experiment was set up, the opening, in 
the right half of the field was carefully closed by a black pad 
and left so over night. The morning light entered the box 
through the left opening only. At a definite time in the 
morning, the glass was removed from the box, and a record 
made of the sporanges already received upon it; the black pad 
was then shifted to the left opening, thus uncovering the right 
opening, and the glass was cleaned and replaced. Care was 
taken not to jar the culture, and the box was kept closed while 
the record was being made. In the evening of the same day a 
second record was made. 
Pig. 15. Chart used in recording' response of Pilobolur to two successive white 
lights. 
By conducting the experiments as just described, the mature 
or nearly mature sporangiophores which have been exposed to 
light from one source are subjected suddenly to light from 
another source; that from the former source being cut off. 
The distribution on the glass of the sporanges at the end of 
+ he experiment will measure the ability of sporangiophores 
at this stage of development to perceive and react to light 
stimuli. 
This work was done during the short days of ^November 
(16 to 27); at this time of year there was little or no dis¬ 
charge of sporanges before 8:00 A. M. The exact time of 
the beginning of the discharge varied greatly with different 
cultures; thus, one had discharged nearly half the total num¬ 
ber of sporanges at 8:30 A. AT., while another had not begun 
to discharge at 10:15 A. M. These variations may have been 
