76 
J. L. WEIMER 
found in cultures grown in an incubator in the dark or wrapped in black 
paper, while in duplicate cultures grown in the laboratory in the light, 
perithecia were formed in abundance. When the culture was ready for 
use the cotton stopper was removed and a large test tube, 37 mm. in inside 
diameter and 243 mm. in height, was inverted over the mouth of the flask. 
The flask and all but the bottom of the tube were covered with black paper, 
to keep out the light. The apparatus was placed upon a desk before a 
north window, where it was exposed to rather strong diffused light. The 
perithecia are positively heliotropic, and hence the spores were discharged 
towards the source of light, namely, the bottom of the test tube. Spore 
masses were found all along the sides of the test tube to a height of 45 cm. 
above the fruiting surface of the culture. None were found on the bottom 
of the tube 5 cm. higher. This is three times as high as previously recorded 
for a member of this family, and 10 cm. higher than given by Buller for 
Ascoholus immersus. So far as the writer has knowledge, this strain of 
Pleurage curvicolla can project its spores to a greater height than any other 
Ascomycete yet studied and three times as high as any other Pyrenomycete 
investigated. 
Considerable attention has been paid by various workers to the study 
of the influence of light upon the direction in which spores are discharged. 
Allen and Jolivette^ have reported in detail, observations made on the 
accuracy with which Pilobolus could project its sporanges toward a source 
of light. While endeavoring to determine the height to which Pleurage 
curvicolla could shoot its spores, the writer incidentally made a few observa- 
tions on its power to aim towards the light. Spore masses have often been 
seen on the side of the petri dish in which this organism was growing next 
to the source of light. In most cases perithecia were present only at or 
near the center of the culture, and these had oriented their beaks in such a 
way as to cause the spores to be discharged in a direction parallel to the 
surface of the substratum on which they were growing. 
In one experiment a two-liter flask containing the fungus growing on 
corn meal was wrapped in two thicknesses of black paper, and a hole about 
2}4 cm. in diameter was cut in the paper on the side of the flask nearest 
the source of the strongest light. After 48 hours a considerable deposit of 
spore masses was present on the side of the flask immediately beneath the 
opening in the paper. The flask was then turned about so that the hole in 
the paper was directly opposite where it had been. This would mean, of 
course, that many of the beaks of the perithecia were pointing directly 
away from the opening. After a period of 48 hours a considerable deposit 
of spores was present beneath the opening in the paper. The paper was 
moved in this manner time after time with the result that each time the 
perithecia changed their aim and discharged their spores towards the source 
of light. 
5 Allen, Ruth F., and Jolivette, Hally D. M. A study of the light relations of Pilobolus. 
Trans. Wise. Acad. Sci., Arts, and Lett. 17: 533-598. 1914. 
