92 BOTANICAL GAZETTE [FEBRUARY 
first sporangiophore became perceptible was not determined. The 
reaction was distinctly visible at 7:45, 30 min. after it was exposed 
to the light. So far as could be seen, the curvature began at the 
tip of the sporangiophore, the tip bending as it grew. The tip 
distinctly started to curve upward at 7:45. This curve was some- 
what more pronounced at 7:50. The tip was vertical, having moved 
through an angle of 45°. The radius of curvature was short. At 
8:40 the tip had grown so that it was no longer vertical, but made a 
smaller angle with the incident light rays. At 9:30 the tip had 
grown around so that it pointed in the direction of the light. It 
had curved about 135° since the beginning of the observation. The 
curvature took place as the growth occurred; the curved end of the 
sporangiophore at this period was a well rounded hook. From 
SOX 
Fic. 1 
this time on the tip grew straight toward the light. The last 
observation on this sporangiophore was made at 10 P.M. and showed 
a pronounced growth in the direction of the light. 
Fig. 1 shows the stages that were sketched. The arrow indi- 
cates the direction of the light. The bending in this case had taken 
place always at the tip, the growing point of the sporangiophore. 
The older basal portion of the sporangiophore appeared to main- 
tain the form and position which it had at the beginning of the 
experiment. If there was any change, it was so slight as not to be 
detected with the microscope. 
The behavior of another sporangiophore under observation at 
the same time was as follows. The reaction was somewhat longer, 
no sign of curvature being noticeable until 8:00 p.m., 45 min. after 
the beginning of the experiment. The bending progressed slowly. 
At 8:40 the tip had curved through 45°, the curve being gradual. 
