58 
Journal of Agricultural Research 
Vol. XXIV. No. I 
Although the vegetative growth of the parasite is retarded at the higher 
temperatures, the data do not indicate that the pathogenicity is reduced 
in like proportion. 
INFLUENCE OF SOIL TEMPERATURE UPON THE GROWTH OF CABBAGE 
seedlings 
Inasmuch as it was presumed at the outset that soil temperature 
affects both host and parasite, it was considered of much importance 
to study separately its effect upon the cabbage plants in noninfested 
soil as well as upon the fungus in culture. The results of the studies of 
the influence of temperature upon the fungus have already been presented. 
In the experiments conducted for the purpose of determining the 
influence of soil temperature upon the seedlings, the general appearance 
of the plants and the dry weight of the shoots and roots were used as 
bases for comparison. For preliminary data use was made of the Wis¬ 
consin Hollander plants whi^ had been grown 20 days in sterilized soil 
as controls on the relation of soil temperature to the occurrence of yellows. 
The methods of planting and controlling the soil temperature will be 
explained in connection with the experiments for studying the influence 
of soil temperature upon the occurrences of yellows. At the end of 20 
days six plants were taken for each temperature and both wet and dry 
weights were determined. The tops were cut off at the surface of the soil 
and dried in a constant-temperature oven for 18 to 24 hours at 95^ C. The 
average results of two such series are given in Table II and shown graphi¬ 
cally in figure 2. These first trials w^ere conducted during February and 
