Mar., 1923] CLAYTON-SOIL MOISTURE AND FUSARIUM WILT 141 
plants were high in dry weight and low in nitrates and sugars. The sus¬ 
ceptible plants, grown under good moisture conditions, were rich in nitrates 
and carbohydrates but low in dry weight. The plants growing in saturated 
soil, which were immune to the disease, showed one striking difference from 
all others—they were almost destitute of nitrates. 
It may be noted that this series was grown during the darkest portion of 
the year, January and February. In experiment III, which was conducted 
at the same time, the blossum buds were all abscised as soon as the 
plants were moved from the cool temperature (i5°-20° C.) to the warm 
temperature (25°-30° C.). In experiment IV, carried on during February 
and March, there was abundant flowering at the medium and high soil 
moistures after the plants had been moved into the warm temperature. 
Since the moisture and temperature conditions were practically the same 
during the two experiments, this difference in flowering may probably be 
attributed to light conditions. In this locality (Madison, Wisconsin) the 
light is very much reduced for several months prior to the middle of Feb¬ 
ruary. After that time, however, there is a rapid increase in the amount 
of sunlight. This increase in sunlight facilitated carbohydrate manufacture 
and changed the carbohydrate-nitrogen ratio, with the result that the plants 
changed from the vegetative to the reproductive condition. This difference, 
however, was not correlated with a difference in the resistance or suscepti¬ 
bility of the plants to wilt, the behavior of the disease being the same in ex¬ 
periments III and IV. 
Experiments Dealing with the Immunity Induced by 
Saturation of the Soil 
After it had been definitely shown in experiment II that the plants 
growing in saturated soil were not subject to the wilt, the reason for this 
relative immunity was investigated. It was soon found that, if these plants 
in saturated soil were allowed to grow under conditions of medium soil 
moisture (25-30 percent) for a short time, their immunity to disease 
was lost. Thus, after the plants had resumed the “normal” type of 
growth, they were attacked by the disease and killed. It was further 
found that the period of time between removal of the plants from the 
saturated soil condition and the date of first appearance of the wilt was 
the same as the incubation period of freshly inoculated plants. This fact 
led to the conclusion that in the case of the plants in saturated soil the 
fungus was able to make little or no progress up the stem of the host as long 
as the soil remained saturated. 
To corroborate these conclusions as to the inability of the parasite to 
grow in the tissues of the plants grown in saturated soil, these plants were 
taken out and dissected at different times. In several instances slightly 
discolored bundles were found in the base of the stem, but in no case was it 
possible to plate out the fungus from the stem. The lower roots of these 
