Jan. 17, 1916 
Plenodomus fuscomaculans 
733 
rack, which had been previously disinfected, rested upon the ground- 
glass base. The bell jar was quickly put in place over the basket and 
sealed air-tight by the use of anhydrous lanolin. Since the air pressure 
at times amounted to several pounds, these bell jars had to be clamped 
to the base plate. This was accomplished by boards drilled at the 
corners, the top one fitted with a 3-inch hole, through which the top of 
the bell jar projected. Long bolts fitted with thumb screws held the 
boards in place and thus when tightened prevented the jars from leaking. 
The air was filtered through cotton before it reached the cultures. 
Several times during the experiment the cultures subjected to dry air 
were moistened with a few cubic centimeters of water. It was found 
that those cultures were nearly dried out at these times. 
No pycnidia were formed with peas, rice, or glucose agar under any 
of the conditions. Other cultures showed the pycnidia in the same rela¬ 
tive proportions for the various conditions of aeration. The record for 
corn broth may be cited as typical. 
TablS XIII .—Effect of humidity: T-est with corn broth under bell jars 
[Time, 30 days] 
Number of pycnidia. 
Growth. 
Medium. 
Unaer¬ 
ated. 
Wet. 
Mostly 
wet. 
Mostly 
dry. 
Dry. 
Unaer¬ 
ated. 
Wet. 
Mostly 
wet. 
Mostly 
dry. 
Dry. 
Com broth. 
O 
Q 
0 
-f 
++ + 
+++ 
+ + + + 
++++ 
+ + + 
+ + 
Pycnidia had been formed for some time before the reading was made. 
The aeration was continued, and a month later another reading was 
made. At this time all the cultures except peas, rice, and glucose agar 
showed pycnidia, irrespective of the air condition, with the exception 
of the series left as a check. This series, left in a battery jar, covered 
with a cotton pad and a glass plate of the same size as the jar, made 
good growth, but in no case did pycnidia occur. 
We have in this experiment results which indicate that at most the 
effect of moist air is to delay pycnidium formation. Whether this effect 
is due to decrease in transpiration or to nutrition conditions, either of 
the substratum or of the aerial mycelium, brought about by the excess 
of water in the air or condensed upon the hyphae is not known, but it 
seems likely that the water relation is the most potent one, since with 
such efficient aeration the transpiration must be considerable in all 
cases. The previous experiments indicated that absence of transpira¬ 
tion was not directly inhibiting to pycnidium formation with cultures 
which were under conditions of scanty nutrition. The last experiment 
reiterates that conclusion, but indicates that the humidity may serve 
to delay fruit-body formation. The effect of moist air in delaying but 
