Allen and Jolimite—Ligfit 'Reactions of Piloholus. 537 
used, fifty to five hundred sporanges are fired each day. The 
glass plate was removed from the box daily and laid upon a 
sheet of paper upon which a target was drawn, the form and de~ 
mensions of which will be described in connection with the re¬ 
spective experiments, and an exact record was made of the num¬ 
ber and position of the sporanges upon that portion of the glass 
plate which corresponded to each area of the target. 
As is well "known, there is a daily periodicity in th© forma¬ 
tion of the sporanges of Piloholus, the ripe sporanges being 
regularly discharged in the morning. The plate on which the 
sporanges struck was removed in the late afternoon or even¬ 
ing. The sporanges had then been all discharged and the 
next day’s crop was beginning its development. One culture 
generally produced three or four crops sufficiently abundant for 
use; occasional cultures produced a large number of sporanges 
daily for more than a week. In the case of series of observa¬ 
tions extending over longer periods than these, new cultures 
were used to take the place of those exhausted. The cultures 
were watered daily at the time when the plates were removed. 
For this purpose, the cultures wore generally taken out of the 
box and then replaced. This was sometimes done late enough 
in the day so that the sporangiophores were sufficiently de¬ 
veloped to have taken a definite position with reference to the 
light. In such cases the culture was replaced as nearly as pos¬ 
sible in its original position. In spite of the utmost care, a 
certain amount of readjustment to the light on the part of the 
sporangiophores was doubtless sometimes necessitated. Ex¬ 
periments to be described below, however, showed that the final 
results of the experiments were in no way affected by the neces¬ 
sity of such a slight re-aiming. 
The Response of Piloboltjs to the Stimulus of 
a Single White Light. 
As a preliminary to the study of the effect of exposure to 
simultaneous stimuli, several series of experiments were made 
in order to learn how accurately tbe sporanges of Piloholus are 
discharged toward a source of light, using various colored lights 
