Apr. 7, 1923 
Influence of Soil Temperature on Fusarium in Cabbage 57 
It is readily seen that if diameter of colony is used as a criterion, the 
optimum^ temperature for growth on potato agar plates for brief periods 
of time is found to be between 24° and 27° C., with a rather sudden 
dropping off toward the extremes. There was no growth at 37°, but the 
fungus was not killed at this temperature, as was shown by transferring 
the plates to an incubator held at 24^. After exposure for 10 days at 24° 
the colonies on the plates w^hich had previously been exposed at 8° and 
37°, respectively, showed vigorous growth. 
Fig. I. —Comparison of rate of growth of Fusarium conglutinans on agar plates with development of yellows 
in cabbage seedlings given in Tables I and V; plants grown 20 days from seed in naturally infested soil. 
In addition to these differences in vegetative growth, the fungus 
exhibited a difference in sporulation at the different temperatures. At 
14*^ C. the colonies were raised, with a leathery stroma, and produced 
abundant conidia. This character became less manifest up to 24°, where 
there was very little aerial growth and there were practically no conidia. 
Above 29° the colonies were again raised and produced abundant 
chlamydospores but no conidia. Table I shows that the growth of the 
fungus dropped off more suddenly above 27° than below, yet it will be 
seen (fig. i) that the percentage of yellows was higher at 35° than at 17°. 
It is evident, therefore, that rate of growth of the fungus in culture is not 
directly proportional to percentage of disease at all temperatures. 
