Allen and Jolivette—Light Ueactions of Pilobolus. 547 
73% at 52 centimeters, and then slowly again to 95% at 94 
centimeters. 
Tn genera], it appears tliat as tlie distance of the culture from 
the source of light increases, there is a decrease in the propor¬ 
tion striking the outer areas. In interpreting these curves, the 
question arises whether at the greater distances the culture was 
entirely out of range. While the cultures vary in the initial 
velocity with which the sporanges are discharged, it has fre¬ 
quently been observed that they can reach an illuminated area 
at a distance of a meter vertically above them, and there can be 
little question that the diminishing percentage which reaches 
the opening in the series described is due directly to failure to 
allow for the effect of gravity on the path of the sporange. 
To determine more exactly whether or not the sporanges fall 
below the opening due to the influence of gravity, the number 
of sporanges was recorded which were found above and below 
the median line already described, when the cultures were from 
50 to 94 centimeters from the opening. 
When the culture was at 50 centimeters distance;, 58 spor¬ 
anges were discharged. 16 sporanges (27.6%) were above the 
center of the opening and 42 (72.4%) below. 
At 54 centimeters, 20% of the sporanges were above, and 
80% below the middle. 
At 82 centimeters only 11.4 were above the center. 
As the culture was moved further from the opening, the per¬ 
centage above the line irregularly decreased while that below 
the line increased. 
The results of this series of observations are given in detail 
in Table II. 
The large percentage below the median line with the culture 
from 50 to 94 centimeters distant corresponds to the decrease 
above noted in the number of sporanges which strike the open¬ 
ing at these distances. It is clear that more and more spor¬ 
anges fall below the median line as the distance from the cul¬ 
ture to the source of light increases. 
The curves (Figs. 5, 6, and 7) showing the distribution of 
the sporanges zigzag back and forth through a rather wide 
range. This is at least partly due to the fact that it is impos- 
