130 PLANT PHYSIOLOGY 
laboratory study (b) after paragraph 146). Keep in the dark 
until the stem and roots are both in a vertical position. Place 
in a box, closed on all sides, except for an opening about 10 
mm. wide at one side, and direct this opening toward a win- 
dow. Note the direction of curvature of stem and roots, as 
well as the region where the curvature occurs. 
(f) Perform experiments similar to the foregoing, placing 
orange-red glass or deep blue glass in front of the opening, and 
note the results. 
(g) Sterilize some fresh horse manure in a steam sterilizer 
to destroy all the fungi, and inoculate with the manure mold, 
Pilobolus. When the sporangia of this are about to be formed, 
place the dish containing the culture, uncovered, in a dark box, 
tilting the dish at an angle of 45 degrees toward one side, where 
a small window about 2.5 cm. in diameter is left open to admit 
light, but covered on the inside with a glass plate. Place the 
box in such a position that the light can enterthe window. ‘The 
sporangia will direct themselves toward the light and discharge 
their spore masses, which will stick to the glass covering the 
window. Only a few shots will fail to hit the ‘‘bull’s eye” 
if the distance from the dish of the fungus to the window is 
not more than 10 to 20 cm., although these are discharged with 
considerable accuracy much further than that. . Try the effect 
of different colored glass on the accuracy of the aim. 
(h) Germinate a number of seeds of 
broom-corn millet or proso (Panicum 
miliaceum) in the dark, in a pot of earth. 
When they have attained a length of 1 to 
- 2cm., cap the tips of half of the seed- 
lings with little caps of tinfoil, made over 
4 the point of a pencil, and then gently 
Fic. 55.—Phototropism slip ped oy. er the tip of the seedling and 
experiment (h). pinched in place. Set the pot in the 
box used for experiment (e), and note the 
result. Almost as good results can be obtained by using oats. 
(¢) Germinate seeds of bean, sunflower, mustard, ete. After 
the seedlings show well-developed cotyledons, fasten several of 
them by their middles in a horizontal position, under a bell-jar 
over water, so as to keep the air moist and prevent the seeds 
from drying out. Keep in a dark place for a few hours and note 
the results, 
ee 
a. (rane 
—— rs 
