Six isolates of F. solani were grown with each temperature regime. 

 Five of the isolates, FlM, F2P1, F3Y, F5P2, and F6P3, were isolated 

 from cankers on hardwood trees. The sixth, F4S, was isolated from soil. 

 All isolates were obtained from the U.S.D.A. Forest Service collection 

 at Delaware, Ohio. 



The fungi were grown on potato dextrose agar in disposable petri 

 plates. The cultures were inoculated by cutting an agar plug from the 

 edge of an actively growing culture with a No. 3 cork borer, and invert- 

 ing the plug in the center of the petri plate. All isolates were placed 

 in the incubator at the same time to insure uniform temperature treat- 

 ment. After 5 days, the mean diameter of each culture was determined 

 by measuring the culture diameter at two locations, at right angles to 

 each other 



The temperature regimes were replicated twice. Each replication con- 

 tained four cultures of each isolate for each of the seven temperature 

 regimes. The data were analyzed statistically in a split-plot design, and 

 comparisons were made with Scheffe's test (i). 



Results and Discussion 



Growth of F. solani varied with the type of temperature program and 

 with the temperature regime (fig. 1). Growth increased with an increase 

 in the range of fluctuations up to 20° F. with the continually changing 

 temperature program and decreased with a further increase in the range 



Figure 1.— Effect of two types of fluctuating temperature programs 



30^ \ 1 1 1 



10 20 30 40 



RANGE OF FLUCTUATION -°F 



