528 
Journal of Agricultural Research 
Vol. XXXI, No. 6 
The ultimate function of these bodies has not been ascertained. 
Those that are exposed to the air serve as bases of sporophore 
tufts. They no doubt also constitute a resistant resting stage of 
the fungus. It was hoped that they might develop into perithecia, 
but no asci have been found. These bodies developed in abundance 
in a large number of infected fruits held about four weeks in a refriger¬ 
ator, but all remained sterile. The infected stem regions were cut 
from these fruits, dried a month, and then incubated in sterilized, 
damp sand at temperatures of 10°, 18°, 22°, 27°, and 31° C. No 
ascus stage developed. However, the sclerotial bodies in the dried 
sepals and under the white papery spots on the fruit produced sporo- 
E hores and spores in abundance. Therefore, it seems that these 
odies may function as a resting stage resistant to desiccation and to 
other organisms. But it is not at all unlikely that other parts of the 
brown mycelial aggregates may function similarly. 
The relation of temperature to the growth of the mycelium on 
potato dextrose agar was determined by inoculating the center of 
each of eight poured plates with a loopful of a spore suspension from 
a strain isolated from leaves, incubating these plates four days at 
25° C., measuring the colonies, and then placing the plates in damp 
chambers in constant-temperature incubators. The increase in 
colony area based on the increase in average radius during 13 days 
was as follows: 0 sq. mm. at 2°, 8 at 10°, 25 at 16°, 55 at 20°, 52 at 
24°, 21 at 27°, 23 at 30 9 , and^ 0 at 35° C. Sporulation occurred at 
all temperatures except 2° and 35° C. The optimum temperature 
for growth was 20° to 24°, exactly as Makemson ( 8 , p. 328) found 
in his tests. He also found that 24° was the optimum for growth 
and sporulation in the living leaves. In a fruit held at room tem¬ 
perature, the black surface discoloration about the stem end in¬ 
creased 4 mm. in radius in three days. In general it may be said 
that the fungus grows rather slowly in culture. 
The relation of temperature to spore germination was determined 
by placing the spores in a drop of sterile tap water or prune decoction 
on a flamed slide in a Petri dish damp chamber and incubating at 
temperatures of 10°, 16°, 20°, 25°, 30°, and 35° C. A high percentage 
(50 to 80 per cent) of germination occurred in water in 20 hours at 
20°, 23°, and 30°, and a low percentage at 10°, 16°, and 35°. The 
germ tubes were short in all cases, but at 43 hours were very long 
at 20° and 25°. At 43 hours there was 80 per cent germination at 
16°. Germination seemed as vigorous in water as in prune decoction. 
These results indicate that the optimum temperatures for spore 
germination represent a slightly wider range than do those for mycelial 
growth. Makemson ( 8 , p. 329) found similar temperatures (18° 
and 24°) optimum for germination in hanging drops of water, and 
noted in infection experiments that long branched hyphae were formed 
after 36 hours. 
RELATION OF FUNGUS TO HOST TISSUE 
The location and distribution of the fungus in the host tissues was 
ascertained by examination of unstained free-hand sections of fresh 
material. The blackened discoloration of the fruit tissue was found 
to be due to the fact that the intercellular spaces were literally packed 
with dense aggregates of dark brown geniculate mycelium (pi. 3, 
