Jan. as, 1917 
Temperature Relations of Apple-Rot Fungi 
143 
INOCULATIONS ON FRUIT 
Great care was taken in selecting the fruit for inoculation, as it was 
found by preliminary experiments that the rapidity of the rot depended 
greatly upon the variety and maturity of the apples. Only fresh, crisp 
fruit was used, and the apples for a particular experiment were all of the 
same lot. Uniformity was obtained by selecting seven apples • (or as 
many as there were temperatures) that were similar in size and degree of 
maturity and distributing these one each in the seven moist chambers 
that were to be placed at the different temperatures, and repeating the 
process until the desired number of apples was obtained. Except where 
otherwise stated, four apples w T ere used at each temperature in each set 
of experiments. 
Care was taken to have the fruit in as sterile a condition as possible. 
The fleshy part of the stem next to the absciss-layer was found especially 
subject to infection by various fungi, and in order to eliminate the possi¬ 
bility of contamination from this source the apple stems were always 
clipped off close to the flesh of the fruit as the first step in preparing for 
inoculation. The frilit was then washed in soap and water, and this was 
followed by immersion in mercuric chlorid (1: 1,000) for three minutes, 
and, finally, the fruit was given a thorough rinsing in sterile water. 
Inoculations were made by forcing the spores or mycelium down into 
the flesh of the fruit by means of a platinum needle. The fruit was 
stored in sterile moist chambers and sufficient moist filter paper added 
to keep the air in a practically saturated condition. The fruit was cooled 
to the desired temperatures within a few hours after storage, even in the 
coldest chambers. Notes were usually taken on the fruit at intervals of 
one week. The records were made as rapidly as possible, so that the 
fruit was kept out of the particular box only for a few minutes. At the 
lower temperatures the notes could be taken still more rapidly in the 
early stages of the experiment, as the results were usually entirely 
negative^ 
The culture of Sclerotinia cinerea used in the first set of experiments ‘ 
(see fig. 1) was from a peach plum from Wenatchee, Washington; one of 
those used in the second experiments (see fig. 2 and 3) was from a prune 
from Vancouver, Washington, and the other from an apple from West 
Virginia. The characteristics of the different cultures indicated that 
S. cinerea had been isolated in each case, but the fungus from apples 
proved a more vigorous rot organism than the others. 
With most of the fungi the various inoculations started off together; 
but with those that were scarcely able to attack the apple, such as the 
species of Alternaria, Cephalothecium, Fusarium,'Pestalozzia, and Tri- 
choderma, there was sometimes considerable difference in the time of 
starting of different inoculations under the same conditions, especially as 
the minimum temperature for the particular fungus was approached. 
In such cases all of the inoculations that were counted at the last of the 
67907°—17-2 
