292 
F. C. NEWCOMBE AND ETTA A. BOWERMAN 
The temperature of the darkroom was kept at 24° to 25° C. The 
aperture in the end of one box was tightly closed by a glass plate held 
in position by a border of heavy paper pasted to the glass and the wall 
of the box. The fan was placed so that a gentle current of air flowed 
obliquely against the aperture end of each box. 
Geotropism. — Three 4-inch pots of seedlings of Brassica alba, 20 
seedlings in each pot, the seedlings raised in the same darkroom as 
that in which the later experiment was made, and having a height 
above the earth of 2.5 to 5 cm., were placed in each culture box in the 
erect position, and so left for 18 hours. Without opening, the boxes 
were now turned so that the included pots were brought into the hori- 
zontal position, the pots having previously been secured to prevent 
rolling. 
Observation at the end of two and one half hours showed in the 
ventilated box 50 of the 60 plants with geotropic angles of 15° to 90°; 
in the closed box, 48 of the 60 showed corresponding curves. The 
angles seemed to average a few degrees more in the closed box, but 
this was only an estimate. No accurate measurements were made. 
Six and one half hours after turning the plants to the horizontal 
position, all the seedlings in the ventilated box and all but one in the 
closed box showed negative geotropic curves of 20° to 90°. A greater 
average angle for either set of plants could not be determined. 
Heliotropism. — Six 4-inch pots of seedlings of Brassica alba were 
raised in the greenhouse to a height of 2 to 3 cm. above the earth, 
then transferred to the dark cabinet last used, and 3 pots enclosed 
within the closed culture box used in the preceding experiment, while 
the other 3 were placed in the ventilated culture box. In this condi- 
tion the 6 pots remained in the dark for 18 hours, the electric fan 
keeping the air of the cabinet in circulation. In order that the plants 
in both culture boxes might have the same amount of light in the 
subsequent stimulation, a glass plate, Hke that used in closing one of 
the culture boxes, was placed inside the other box and 4 cm. distant 
from the aperture, so that all light which reached the plants had to 
pass through similar glass in each box, but the current of air could 
enter one box and not the other. 
A single tungsten lamp of 25 watts was used for both boxes, the 
boxes being set with their long axes pointing toward the lamp. The 
middle of the pots in each box were respectively 25, 38, and 51 cm. 
distant from the lamp. The temperature was 24° C. 
