Jan. 17, 1916 
Plenodomus fuscomaculans 
73 i 
seem extremely probable. It was seen that cultures on various complex 
media did not produce pycnidia until they began to dry out, as a general 
rule. Moreover, on nutrient solutions the pycnidia commonly form on 
the surface. On vegetables, such as carrot or parsnip, or on prime- 
juice agar, the pycnidia formed in the aerial mycelium. 
Very early this relation was suspected as being operative, and the 
filter paper cone was used in the first experiments to further transpira¬ 
tion and aeration. When, however, the relation was tested, it was seen 
that the actual formative influence of transpiration had been greatly 
overestimated. Filter-paper cones were compared with similar-sized 
disks of filter paper entirely submerged. Inoculation was made with 
bits of mycelium, and the cultures stood on the table in strong diffuse 
light. 
Table XI .—Effect of humidity: Test with filter paper 
[Time, 1 month] 
Conditions. 
Number of 
pycnidia. 
Growth. 
Cones mostly above water. 
5-IO 
10+ 
Fair. 
Submerged paper. 
Scanty. 
It is seen that the pycnidia production goes on after this period as 
strongly, if not better, in the submerged condition, while the growth 
seems slightly stronger on the cone. Since differences of this sort are 
hard to estimate, little importance is attached to the slight differences. 
Nevertheless, we have in this experiment striking evidence that under 
conditions where transpiration is reduced to the zero point pycnidium 
production is nevertheless vigorous. 
In this experiment the possible relation to contact stimuli is not 
avoided. The following observation is even more conclusive, for here 
contact relations are limited to the effect of mutual contact of the threads 
of the mycelium itself, and no further elimination of a hypothetical con¬ 
tact relation is possible. Several water blanks of ordinary distilled 
water were heavily inoculated with spores and mycelium, respectively. 
After a month the following observation was recorded: 
Table XII .—Effect of humidity: Test with inoculated water 
- • 
Form of inoculation. 
Number of 
pycnidia. 
Growth. 
Spores. 
4-10 
2-10 
Fair amount of white, byssoid mycelium. Total 
submergence. 
Fair amount of white, cottony mycelium. Total 
submergence. 
Mycelium. 
