Mar. 3,1923 
Gray Mold of Castor Bean 
703 
Most of the inoculations were made, however, at Orlando, Fla., on 
developing inflorescences of large growing plants. Since the nature of 
the plant demanded special methods, these will be given in detail. The 
method most used was one obtained from J. R. Winston, who used it 
extensively in his work on citrus diseases. For an inoculation chamber a 
sheet of ordinary waxed paper was used. First a wad of cotton was 
wetted and wound about the base of the inflorescence to supply moisture. 
Then the inoculum was applied in the particular form to be tested, and 
the whole was promptly covered with the waxed paper in the manner 
depicted in Plate 8, A. First, the sheet was folded lengthwise about the 
stem, and the vertical edges were brought together and folded twice 
with narrow folds and creased firmly. Then the upper part was folded 
down and brought around the stem and held tightly in place with one or 
two ordinary paper clips. In this way a tight moist chamber was secured 
in a very short time. It was thrown away at the end of the desired incu¬ 
bation period. 
For inoculations with ascospores, it was necessary to be absolutely sure 
that no conidia were present. A few preliminary tests on plants under 
natural conditions made it evident that it would be difficult with ordinary 
methods to insure sterility of parts of the plant to be inoculated. A waxy 
bloom covered practically the whole plant, and particularly the inflores¬ 
cence and prevented the spread of solutions of mercuric chlorid applied 
for the purpose of sterilizing the surface. This difficulty was overcome by 
using this sterilizing agent in solution in 35 or 40 per cent alcohol. 
Immediate and complete contact was obtained in this way, and it was 
determined that 20 seconds* immersion would not injure the plant. This 
treatment was followed immediately by dipping the part treated, usually 
the inflorescence, into freshly drawn tap water, which removed the alcohol 
and mercuric chlorid, and left the plant evenly wetted, an additional 
advantage when it came to applying the inoculum. 
In May, 1919, no natural infection had as yet become evident in the 
experimental plantings near the laboratory at Orlando, Fla., where 
inoculations were made. Conditions were the better, therefore, for 
reliable results. A series of 10 inoculations, with an equal number of 
controls, was made on castor bean spikes in different stages of develop¬ 
ment after the methods outlined above. The plants were not sterilized. 
Conidia from young cultures in Petri dishes were used for most of the 
inoculations. Transfers containing mycelium and some of the culture 
medium were used in others. Eight of the 10 inoculated flower clusters 
showed, at the end of 48 hours, definite signs of infection. The two fail¬ 
ures had dried out, owing to insufficient sealing of the paper moist 
chamber. None of the controls were infected. Typical inoculated in¬ 
florescences, removed from the plants and placed in flasks of water under 
bell jars in the laboratory, developed a heavy growth of gray mold very 
similar to its appearance in nature. Those lrft exposed, out of doors, 
failed to progress. The rainy season had not yet started sufficiently to 
develop and spread the disease. 
Several more inoculations were made at this time, with different strains 
of the organism, including reisolations from previous inoculations and 
cultures derived from ascospores. Practically all of them were successful, 
and the controls remained healthy. 
On May 20, inoculations were made with ascospores as follows: Several 
apothecia were crushed in sterile water and the resulting suspension of 
ascospores, asci, etc., were applied to castor bean inflorescences not pre- 
