572 Wisconsin Academy of Sciences , Arts , and Letters. 
due to differences in the morning illumination, to weather con¬ 
ditions, or to the fact that some cultures were shaded more 
than others on the afternoon before being used. That the 
light supply had something to- do with it seems probable, be¬ 
cause the development of a crop of sporanges can be retarded 
considerably by placing the culture in a dark room during 
the afternoon and night. 
In the experiments in which the light was changed at 7:15, 
7:30, 8:00, 9:45 and 10:15, no sporanges had been discharged 
at the time of the change. (Table X). In the other experi¬ 
ments of this series, some of the sporanges were found upon 
the glass in the morning. In the latter cases, the results 
were of the same character as those previously obtained when 
a single light was placed a little to one side of the culture 
(Fig. 13). The culture was closer to the opening- in the 
present series, and so the sporanges were better centered about 
the opening. Only about one-eighth of the sporanges (13%) 
lay between the opening and the middle line of the field. 
Very few sporanges lay in the right half of th© field. 
Of the sporangiophores still carrying sporanges when the 
position of the light was changed, the majority began to bend 
over toward the new source of light and in many cases the re- 
aiming was completed before their discharge. 
The experiment (Table X) in which the direction of the 
light was changed at 9:15 A. M. may be taken as a typical 
example. When the box was opened at 9:15 A. ML, we found 
63 sporanges on the glass. Of these, 40 were upon the open¬ 
ing, 8 to the left, and 10 to the right but still in the left 
half of the field, while 5 scattered sporanges were on the right 
half of the field. The glass was cleaned and replaced, the 
left-hand opening closed and the right-hand one opened. 
In the evening, we found the remainder of the crop of 
sporanges (68) on the glass. The distribution of these was 
as follows: (1 is the closed left-hand aperture, 2 the open 
right-hand aperture) :— 
