Allen and Jolivette—Light Reactions of Pilobolus. 579 
anges. Sixteen candle power incandescent lamps were used as 
sources of light and were kept before the opening day and night. 
The culture was placed upright in a saucer containing water to 
prevent it from drying out, and was set on the floor of the box 
in line with the two openings. The culture was. first placed 
two centimeters from one end of the box, and on each succeed¬ 
ing day was moved two centimeters toward the opposite end. 
The number and position of the sporanges fired while the cul¬ 
ture wlas in each position were recorded. The surface of the 
culture was six centimeters below the level of the centers of the 
two openings. The angles at which the light from the respective 
openings strikes the sporangiophores vary with the position of 
the culture. To obviate the possible shading of some of the 
sporangiophores, care was taken to use cultures, with an even 
surface and with sporangiophores symmetrically arranged. 
As the culture is moved from one end of the box toward the 
other, the intensity of the light received from one opening is of 
course decreased while that from the other is proportionally 
increased. By recording the number of sporanges found on 
each glass at each stage in the series, we can determine the ratio 
of the effectiveness of the two kinds of light. 
In the experiments to be described, we compared the effects 
of light coming through respectively (1) the blue and the white 
glass, (2) the blue and the yellow glass, (3) the ammoniacal 
copper oxide solution and the bichromate solution, (4) the blue 
and the red glass, and (5 ) the white and the red glass. 
In the series in which the blue and white glasses were used, 
the bull’s eye target, Big. 3, was used, the inner circle being of 
the same size as the opening. The radius of each circle was 
one centimeter greater than that of the circle next within. The 
areas were numbered outward from 1 to 3, beginning with the 
inner circle. Area 3 included all outside of area 2. More 
circles were unnecessary, since relatively few sporanges were 
found outside of area 2. A horizontal line was drawn through 
the center of area as before, so that a record could be made of 
the sporanges striking above and below the center. In these 
preliminary experiments, no attempt was made to compare ab- 
