Jan. 22,1917 
Temperature Relations of Apple-Rot Fungi 
155 
Petri-dish experiment. —It was found much more satisfactory to 
test the growth of the fungi on agar in petri dishes than by the use of 
flasks. Growth was more uniform, more easliy measured, and the 
results apparently were more reliable. In these experiments corn-meal 
agar was used for all of the fungi. The culture medium was poured into 
the dishes, and inoculations were made near the center of the plates as 
soon as the agar had cooled. Plates were made up in duplicates in all 
cases. They were allowed to stand in the laboratory for 24 hours after 
inoculation had been made and were then placed at the various tem¬ 
peratures indicated. In the first series of experiments no measurements 
of the colonies were taken at the end of this first 24 hours, but records 
were made after 4, 6, and 17 days. Figure 24 shows the results obtained 
at the end of 6 days after inoculation. In the second series of experi¬ 
ments measurements were taken at the end of the 24 hours at laboratory 
temperature and later measurements at the times indicated. The rate 
of development of the various fungi in this experiment is shown in figures 
14 to 23. The graphs show the increase in the diameter of the colonies 
at the end of 2, 4, 6, 8, 18, and 34 days from the time of placing the 
cultures at the given temperatures. The comparative temperature 
responses of the different fungi is brought out in figure 25. In this 
figure the curves show the average daily increase in diameter after the 
end of the first day in storage. By not including the growth made in 
the day at laboratory temperature nor the growth in the first day at the 
storage temperatures it was thought that a more accurate record of the 
temperature responses of the fungi would be obtained. The base line 
represents temperature in all cases, and the perpendicular the diameter 
of the growth in millimeters. 
A study of figures 14 to 23 as compared with figures 4 to 12 makes it 
evident that the rate of growth did not increase with time in the petri- 
dish experiments as it did in the experiments with apples, the fungi, 
with the exception of Sphaeropsis malorum , making as great increase in 
growth at both low and high temperatures during the first days of the 
experiment as they did during the later ones. 
In comparing the growth on apples with that on corn-meal agar it 
will also be noted that in the latter case fewer of the fungi show a ten¬ 
dency to lower the minimum with the longer periods of time. This is 
partly accounted for by the fact that more of the fungi grew at the 
lower temperatures on the com meal from the beginning of the experi¬ 
ment. Fusarium radicicola had made no evident growth on apples at 
15 0 after five weeks nor Glomerella cingulata on apples at io° after eight 
weeks, but both grew on com-meal agar at 5 0 from the first. Neofabraea 
malicorticis and Penicillium expansum made no growth on apples at io° 
after two weeks, but the former grew on com-meal agar at o° from the 
beginning of the experiment and the latter had made a start at that 
temperature by the end of the fourth day. Volutella fructi had made no 
