576 Wisconsin Academy of Sciences, Arts, and Letters. 
sporangiophores failed to begin to respond to tlie new, stimulus,, 
and nearly half of them completed the reaction. 
These data demonstrate that perception and reaction can take 
place in fully mature sporangiophores; that a heliotropic bend¬ 
ing can take place when the sporang© is about to be discharged, 
and that the reaction can be interrupted at any point by the dis¬ 
charge. 
W,e next attempted to determine to what extent sporangio¬ 
phores, subjected to two light stimuli, turn toward the nearer 
source of light. The surface of the culture used was five centi¬ 
meters in diameter. The culture being placed, as before, equi¬ 
distant from the two openings, if the openings admit exactly 
the same amount of light, only those sporangiophores which 
happen to be on the median vertical line of the culture will be 
equally lighted from the two directions. Placed at either side 
of the middle line, the sporangiophore will be nearer to one 
opening and farther from the other. The following experi¬ 
ments were devised to show to what extent, if at all, the spor- 
anges on the right half of the culture are discharged at the left 
hand opening, and vice versa. 
The apparatus used was a wooden box 39 centimeters long, 
23 centimeters wide and 16 centimeters high. Two openings 
two centimeters square were cut in one end, eight centimeters 
apart and four centimeters from the bottom of the box. The 
culture lay on the bottom of the box, its surface vertical and 
facing the end containing the openings and its center equidis¬ 
tant from the openings. The distance from the center of the 
culture to the center of either opening was ten centimeters, 
making the angle between the two beams of light reaching the 
culture about 45°. The sporanges were caught on two plates 
of glass. One, as usual, was placed inside against the end of 
the box (covering the openings) and the other was placed ver¬ 
tically, perpendicular to the first glass at its median line and 
extending back until it touched the median line of the culture. 
Figure 16 is a diagram of a horizontal cross section of the box. 
With this arrangement, any sporanges discharged from the left 
half of the culture towards the right opening or from the right 
half to the left opening will be intercepted by the second glass. 
