Jan. 17, 1916 
Plenodomus fuscomaculans 
721 
mentioned. Many had studied the effect of light upon germination, but 
the varying intensities of light used, etc., yielded nothing in the way of a 
generalization. 
Elfving (1890) sought to find the influence of light upon metabolism. 
He used cultures of Penicillium spp. and a related fungus (Briaraea sp.) 
growing in a synthetic solution. He used several sources of carbon and 
nitrogen. Basing his conclusion upon the dry weights obtained in the 
light and in the dark, he decided that light acts upon fungi as an inhibitor 
of organic synthesis. The closer the food material is to protoplasm in 
its make-up, the less the light inhibits. This produces the result which he 
finds analogous to conditions in the higher plants—that light restricts 
vegetative growth. Elfving, in view of the great similarity of fungi in 
their physiological relations, boldly makes his conclusions apply to the 
whole group of fungi. 
Tendner (1896) tested the effect of light upon species of Mucor, 
Botrytis, Amblyosporium, and Sterigmatocystis, finding that light was 
effective only under conditions of unfavorable nutrition. 
Finally, in the experiments of Temetz (1900) with Ascophanus carneus , 
asci were produced only under the influence of light. 
Tight is seen to be a factor of widely varying importance _or organisms, 
although the effect on vegetative growth is commonly shown to be pre¬ 
judicial. For some it is a morphogenic factor of great influence; for 
others it is of no moment. 
Pure cultures of the organism on prune-juice agar and on parsnip had 
been brought from the Agricultural College laboratory. At Ann Arbor 
these cultures began to produce pycnidia in a few days. When analyzed, 
this striking behavior showed that light was probably the factor concerned 
with the fruit-body formation. The following experiments were started 
to test the validity of this inference. While work at the Agricultural 
College had been done some distance from the window (25 to 30 feet), 
the cultures at Ann Arbor were placed a few feet from a south window 
in strong diffuse daylight, and at times in direct sunlight. 
Experience had shown that the organism would make a fair growth on 
filter paper. Filter-paper disks, about 5 cm. across, were folded to form 
cones, and these were set up in 10 c. c. of tap water in preparation dishes. 
These were autoclaved. To some, one drop (1/20 c. c.) of a sterile M/i 
chemical was added, as indicated in Table III. The preparation dishes 
were inoculated with a mycelium suspension, and were placed in tall 
battery jars covered with filter paper. One set of cultures was placed 
in a light-tight cupboard, while the other was left upon the table in 
strong diffuse light. Thermometer readings showed at times of strongest 
light that the illuminated cultures were 2 degrees centigrade warmer than 
those in the dark. Readings were made in nine days. 
