Jan. 17, 1916 
Plenodomus fuscomaculans 
725 
The production of sclerotia, as recorded in Tables II and III, after a 
short exposure to light, and the production of pycnidia in one case, where 
the exposure was not more than two hours, suggested that the exposure 
to light did not need to be of long duration in order to produce its mor- 
phogenic effects. The capsules of a preceding experiment, which had 
shown no pycnidia after three weeks in the dark chamber, were divided 
into series, one of which was exposed to strong diffuse light on the window 
sill for two hours, while the other series was continued in the dark box. 
The exposed cultures were returned to the box, and after a week the 
cultures were examined. 
Table VII .—Effect of light; Continued test with corn broth 
Com broth. 
Mature 
pycnidia. 
Growth. 
Dark. 
0 
Aerial growth. 
Aerial growth checked, 
mycelium matted. 
Dark, light (2 hours), dark. 
3“4 
Pycnidium production had not increased upon a second examination a 
week later. 
This experiment teaches that pycnidium formation is not only associ¬ 
ated with light, but that the effect of light is to inaugurate a type of 
growth which can proceed to completion even in the absence of light. 
But after exposure to light the number of fruiting bodies formed is limited 
and the process does not continue to the production of a large number of 
fruiting bodies. 
To summarize the results of this series of experiments, it may be 
pointed out that light is a decisive factor, which determines, in certain 
cultures, whether reproduction takes place or not, and that the action 
of this factor is irrespective of the richness or the poverty of the sub¬ 
stratum in nutrients. As a morphogenic factor, its action is to inaugu¬ 
rate fruit-body formation, but it is not essential to the process, once 
inaugurated. Associated with its effect in initiating reproduction, we 
have its repressing effect on growth. 
All subsequent cultures made with the organism had good exposure to 
strong diffuse light, unless otherwise expressly stated. 
TEMPERATURE 
It has been said that the influence of temperature was very early 
recognized in its influence on the life processes of fungi. Raulin (1869) 
in his studies of Aspergillus niger grew the organism at the most favor¬ 
able temperature—33 0 . Wiesner (1873) very early formulated the 
behavior of Penicillium glaucum by a law which took into account that 
the time necessary for fructification did not depend wholly upon the 
