Mar. 3,1923 
Gray Mold of Castor Bean 
691 
most frequent form was that pictured in Plate 12, F, a reproduction from 
a camera-lucida drawing. This is a special branch arising from the 
sterile hypha imbedded in the substratum. In another type the 
cluster of conidiophores arises directly on a cell of the sterile hypha 
(jo, PI. XLI , e). In still another form a long, slender branch 
bears upon its tip either a single conidiophore or a group of them, 
with the microconidia on their tips. Microconidia were observed to best 
advantage on germinating ascospores, as shown in Plate 12, G, and photo- 
micrographically in Plate 10, C. From one or two to more than a dozen 
microconidia may develop in succession on the end of a single conidio¬ 
phore, those that are mature dropping off and forming a distinct group. 
In general, the microconidia are very similar in all respects to those de¬ 
scribed by Brierly (2) for Botrytis cinerea. No germination was seen, 
however, though looked for diligently. No endoconidia were observed. 
It was not deemed profitable to grow this organism on a long series 
of culture media, since its growth was almost equally vigorous on most 
media commonly used in the laboratory. There were a few specific differ¬ 
ences evidenced that should be recorded. On corn-meal agar heavy pro¬ 
duction of the gray mold occurred, with comparatively little development 
of white mycelium and only occasional sclerotia. On potato agar, also, 
sclerotia were not abundant, but more mycelium was evident. Oatmeal 
agar at first produced a profusion of conidia, but later this appearance 
was hidden by more or less of the white mycelium and a great abundance 
of sclerotia. This was the medium most commonly employed for the 
development of sclerotia. Boiled rice and potato plugs had fewer 
conidia, but sclerotia were abundant. Beyerinck's agar produced a thin 
growth of conidia and few sclerotia. Sterilized sweet clover stems pro¬ 
duced large sclerotia and few conidia. The interesting fact was noted 
that some media at times produced a heavy mat of conidiophores and 
conidia but no sclerotia at all. Transfers were made from such tubes to 
oatmeal agar to determine whether this was a character peculiar to the 
particular strain ef the fungus. In every case a normal heavy develop¬ 
ment of sclerotia was produced on the new medium. 
The cardinal temperatures for the growth of the gray mold on corn- 
meal agar are as follows: Minimum, 12 0 C.; optimum, 25 0 C.; maxi¬ 
mum, 35 0 C. 
f DEVELOPMENT OF THE PERFECT STAGE 
PRELIMINARY EXPERIMENTS 
Before there had been any intimation of the existence of a perfect stage 
of this organism, attempts were made to induce sclerotia to fruit or other¬ 
wise function. 
Experiment I.—On February 6, at Orlando, Fla., three Petri dishes of moist sand 
were sterilized and sclerotia from cultures of strains B 35 and B 37 placed thereon, and 
the whole placed in an incubator at 27 0 C. Observations were made for several days 
without noting any developments other than the production of gray mold from the 
medium at the edge, that had been carried over with the sclerotia. The plates became 
dry, and finally on March 16 sterile water was added and the plates were further 
treated as follows: No. 1, in the ice box for 24 hours, then under a glass moist chamber 
out of doors under fluctuating but on the whole fairly warm temperature conditions. 
No. 2, submitted to a — io° C. temperature in a freezing mixture for a few hours, the 
temperature gradually rising to + io° C., after which it was placed out of^doors along 
with No. 1. No. 3, was placed directly under the out of door conditions. 
