98 BOTANICAL GAZETTE [FEBRUARY 
same region. The bending continued until 5:30 a.M., when the tip 
of the young sporangium pointed directly toward the light. The 
entire portion between the region of bending and the young sporan- 
gium was swollen slightly, showing the beginning of the formation 
of the vesicular bulb. At 6:30 the vesicular bulb was large and 
turgid (fig. 12). 
At the beginning of the observation the second sporangiophore 
in the same field of the microscope was somewhat longer than the 
first and the sporangial swelling was well formed. This sporangio- 
phore also formed an angle of 90° with the light. The vesicular 
bulb was not yet visible. At 2:15 the sporangiophores had curved 
through an angle of 20° nearer to the direction of the incident light 
rays. The curvature in this case was also at some distance below 
the sporangium swelling, and the space between the two was 
WELT 
beginning to show signs of the formation of the vesicular bulb. At 
5:30 A.M. the tip of the sporangium was aimed toward the light. 
The vesicular bulb was still very inconspicuous. The bend in the 
sporangiophore was well rounded and had grown in length since the 
beginning of the curving. At 6:30 the vesicular bulb had swollen 
so that it exceeded the diameter of the sporangium by twice the 
diameter of the latter. At 8:00 the development appeared fairly 
complete. The sporangium was discharged between 9:50 an 
10:00 A.M. (fig. 12). 
From the foregoing experiments the following conclusions are 
evident: 
1. Growth takes place at the tip in the young sporangiophore. 
2. It is in the growing tip that heliotropic curvatures are formed. 
3. In no case has a heliotropic curvature been observed during 
stages in early sporangium-formation. 
