PLATE 3 
INFLUENCE OF SOIL TEMPERATURE AND SOIL MOISTURE UPON 
CLUBROOT OF CABBAGE 
These plants correspond to those in Plate 2, but* were grown in infested soil. 
Note that clubs occur only on roots grown in wet soil at 9°, 12°, and 15° C. 
The plants were grown in soil taken from the same sample of sandy loam 
(soil B of text, p. 552) uniformly infested with the clubroot organism and of a 
nature favorable for the development of the disease. The air temperature for 
all alike was about 15° C. 
Plants in the upper group were grown in soil kept uniformly at a high moisture 
content of 90 per cent of the water-holding capacity. Those below were grown 
in soil kept at a moisture content of 45 per cent of the water-holding capacity. 
The absence of clubbing in the roots from the dry soil at the three higher tem¬ 
peratures as compared with corresponding ones in the wet soil must therefore be 
due to the inhibiting influence of low soil moisture. 
The influence of soil temperature on clubbing and on growth as shown in 
the upper group is similar to the series in soil A (Plate 1) with the exception of 
that grown at 9° C. In the latter case no clubbing occurred at 9°, but in this 
soil slight clubbing developed at 9° C. 
