Jan. 17, 1916 
Plenodomus fuscomaculans 
757 
table. The cultures in the dark were placed in the dark chambers 
described on page 723, and those in the light were placed in battery jars 
with tilted covers. 
Table XXVIII. —Effect of change of intensity of a factor: Change in temperature 
Pycnidia. 
Growth 
Conditions. 
One 
week. 
Two 
weeks. 
increment, 
two weeks. 
Room temperature (22 0 ): 
Dark. 
O 
O 
++++ 
++ 
++ 
++ 
Dight. 
0-4 
0 
25-50 
O 
Approximately io°: 
Dark. 
Light. 
IO-I 5 
IO-25 
The conditions were continued for two weeks longer without any 
change in the relations. This experiment reinforces the conclusion 
just arrived at that light has some other action than a mere checking of 
growth, and its action can not be replaced by a mere checking of growth. 
Light is known to have a powerful oxidizing effect, and organic material 
under the influence of light is subjected, according to Freer and Novy 
(1903), to the action of organic peroxids engendered by the catalytic 
action. 
The following experiment was tried to determine whether some such 
action was concerned. Hydrogen peroxid was added to 12-day-old 
corn-broth cultures at the rate of 2 drops (1/20 c. c.) of a 3 per cent 
solution to a dish. The experiment was checked with cultures of the 
same age. The dishes were placed in a dark chamber. After a week 
(first examination) the result shown in Table XXIX was obtained. 
Table XXIX. —Effect of change of intensity of a factor: Addition of hydrogen peroxid to 
corn broth 
Medium. 
Pycnidia. 
Com broth -f- hydrogen peroxid (H 2 0 2 ). 
+ a 
Com broth, check. 
<*4 to 8. 
By strongly oxidizing cultures with hydrogen peroxid it was possible 
to replace the morphogenic action of light. Light, therefore, must act in 
some such manner upon this organism, and the action in fruit-body for¬ 
mation must be of some such character. This experiment was repeated 
at least six times, with varying concentrations of hydrogen peroxid. 
With cultures grown in the dark for from two to three weeks, the addition 
