Dec., 1923] 
SHERWOOD — FUSARIUM WILT OF TOMATO 
547 
appearance they were very similar to those in flat no. 1 which contained the 
most acid soil in the series. 
In flat no. 3 of the silt-loam series a very low percentage of infection 
occurred. This may be due in part, at least, to the fact that the soil in this 
flat was somewhat drier than in the others at the time of planting the seed. 
The conspicuous contrast in the condition of the plants in flats nos. I and 5 
of the sandy-loam series is shown in Plate XXXVIII. The photographs 
were taken on May 7 just before harvesting. 
Experiments with Fusarium on Culture Media 
Experiment 1 
These experiments were designed with the view of studying spore ger¬ 
mination and mycelial growth of Fusarium lycopersici in culture media 
adjusted to various hydrogen-ion concentrations. The purpose of the ex¬ 
periments was to determine whether under different reactions any corre¬ 
lation exists between the growth of the fungus in culture and its behavior in 
soils as expressed by the development of the disease in the plants. 
After some preliminary experiments in attempting adjustments of vari¬ 
ous liquid media, it was decided to use a medium made from “Difco” pep¬ 
tone, 1.0 percent; dibasic potassium phosphate, 0.5 percent; dextrose, 3.0 
percent; and distilled water, 1000 cc. Tests showed that the fungus would 
grow well when this medium was adjusted to plus 1, Fuller’s scale. More¬ 
over, it was found that adjustment could be made from pH 1.2 to 10 without 
the presence of any precipitate. Also, the natural color could be practically 
destroyed by one-half dilution with water, making the colorimetric deter¬ 
minations an easy matter with the use of the comparator. 
Culture flasks were prepared in duplicate. Two hundred fifty cubic 
centimeters of the medium was placed in Erlenmeyer flasks of about 300 cc. 
capacity and adjusted with additions of sodium hydroxide or hydrochloric 
acid to the desired hydrogen-ion concentration. After the adjustment was 
made, 25 cc. was removed and placed in tubes to be tested after sterilization 
in order to determine the final reaction. The medium remaining in the 
flasks was then divided into two equal portions in flasks for inoculation. 
Culture flasks and tubes were sterilized together at seven pounds’ pressure 
for thirty minutes. For inoculation purposes a water spore suspension was 
prepared from a pure culture of the organism on oat agar. One cubic centi¬ 
meter of this suspension was placed in each flask with a sterilized pipette. 
The cultures were incubated in the greenhouse where the tomatoes were 
growing, and thus exposed to the same temperature. The flasks were kept 
covered so they would not be exposed to strong light. After a period of 
fifteen days the relative amount of growth was noted. The contents of the 
flasks were then filtered, with moderate suction, through the Schleicher and 
Schiill ashless filter paper, and the hydrogen-ion concentration of the fil- 
