Mar. 3, 1923 
Gray Mold of Castor Bean 
697 
Lot 2 was placed on sand in a small shallow box which was sunken till the top was 
flush with the ground under the east edge of the laboratory. It was watered occa¬ 
sionally, but at times the sand was quite dry. Finally, on May io, a few very small 
apothecia were found. 
Lot 3. On April 15 field sclerotia were placed in marked locations in a castor bean 
field under natural conditions. On June 2, after several days of continuously wet 
weather, a few apothecia were found to have developed. 
It would seem that a moist substratum alone is not sufficient but that 
also a moist atmosphere is necessary for the best production of apothecia. 
It would also seem that too high temperature is capable of inhibiting the 
development of apothecia. 
Experiment XI.—It has been noted in experiment III that single ascospore cul¬ 
tures from second-generation apothecia had been made. The development of scle¬ 
rotia was so prompt in these cultures that it seemed possible to place these sclerotia 
under favorable conditions and get still another and perhaps several more generations. 
Early in July, 1919, this was done. Before the end of the month a third generation 
of apothecia was produced. A mature apothecium was laid on its side in a poured 
plate of clear agar and left several hours. When the cover was lifted the apothecium 
shot forth a cloud of spores, which were, of course, caught on the surface of the agar. 
Single ascospores were isolated and further cultures started. These, too, produced 
sclerotia which produced another crop of apothecia, this time within 30 days of the 
time the single ascospores were isolated. Thereafter this process was continued, at 
first in Florida and later in Washington, D. C., whenever time permitted, in some 
cases after delays of several months. In July, 1920, the eighth consecutive generation 
of apothecia was produced, but there was then no opportunity to secure single asco¬ 
spore isolations. This was accomplished in August. At the same time, following a 
suggestion from Prof. W. B. Brierley, of the Institute of Phytopathological Research, 
Harpenden, England, who was then a visitor in America, single conidia taken from 
the seventh-generation single ascospore cultures were isolated to determine whether 
they, too, could develop tne perfect stage. These cultures were placed in racks in 
the laboratory. After three, months* absence, the writer returned and found that 
many of the tube cultures, both single ascospore and single conidium, had produced 
apothecia in the tubes. These, however, had shriveled and become covered with 
conidia and mycelium. Consequently in November new single conidium isolations 
were made. In addition, castor bean plants in the greenhouse were inoculated with 
the seventh-generation strain, the typical disease was produced, and single conidium 
isolations were made, directly from the host. At this time, also, mature eighth- 
generation apothecia were available, and single ascospore isolations were made from 
them. Transfers of all three strains were made to several tubes of oatmeal agar, and 
in due time an abundance of sclerotia developed. On December 15, several sclerotia 
were transferred from each lot to Erlenmeyer flasks of moist sand. In addition, 
sclerotia that had been collected in the field at Orlando, Fla., in July, 1919, were placed 
under like conditions. All the flasks were placed in the greenhouse. After several 
weeks an examination disclosed that every one of the four strains had borne mature 
apothecia. 
Thus ninth-generation apothecia were procured, each generation after 
the first having started from a single ascospore; single conidium strains 
from two sources both produced normal apothecia; and field sclerotia a 
year and a half old did likewise. All four strains were used to start new 
single ascospore cultures according to the usual method. Plate 10, C 
and D, were taken from two of these plates. 
Eventually tenth-generation apothecia were developed, and ascospores 
were sown and isolated from them. In the entire series there appeared 
to be not the slightest change in appearance in culture, as compared with 
more recent isolations, or in ability to develop all the life-history stages. 
INFLUENCE OF LIGHT ON APOTHECIUM DEVELOPMENT 
In all this work the conclusion could not be escaped that the produc¬ 
tion of apothecia was much more readily accomplished in the summer 
months than in the winter. It was very rarely that apothecia were 
