554 Wisconsin Academy of Sciences, Arts, and Letters. 
tant from the source of light, the curve closely follows that 
for the white light at the same distances. There is a gradual 
decrease in the percentage of sporanges on the opening as the 
distance from the culture to the opening increases. The curves 
for the percentages on areas 3 and 4 (Figs. 6 and 7, dot—dash 
line) also present a remarkable similarity to the corresponding 
curves for the same areas when white light was used. With 
the culture at 16 centimeters and at greater distances, the per¬ 
centages on areas 3 and 4 gradually increase because the in¬ 
fluence of gravity tends to make the sporanges fall below the 
opening. From these experiments it appears that Pilobolus 
fires its sporanges with about the same accuracy toward blue 
light as toward white light. 
A yellow glass was next substituted for the blue, the culture 
being placed 20 centimeters from the opening one centimeter in 
diameter. The target shown in Figure 1 was used in count¬ 
ing the sporanges. The total number of sporanges found on 
the glass plate at the end of twenty-four hours was 52, of which 
8 (15.4%) were on the opening, 20 (38.4%) were on area 2, 
1‘5 (30%) on area 3, 4 (7.8%) on area 4, and 5 (9.6%) on 
area 5. The percentages in the outer areas are rather large 
compared to those for the same areas, when the blue or white 
light is used. It appears at once that the reaction of Pilobolus 
to yellow light is much less accurate than to either blue or white 
light. 
A four-centimeter opening was then tried in place of the 
one-centimeter opening. The target’used in this experiment is 
the same as that shown in Figure 3. 98 sporanges were found 
on the glass, of which 32 (32.6%) were on area 1, 27 (27.3%) 
on area 2, 14 (14.2%) on area 3, and 25 (25.5%) on area 4. 
Thus 60% were on the, opening, the remainder being widely 
scattered. In the corresponding experiments with blue and 
white light, 97.2% and 94.5% respectively were found on the 
opening. 
The response to yellow light was further tested in a series 
of experiments with the opening four centimeters in diameter 
