PATHOGENICITY OF H. SATIVUM ig 



SPORE GERMINATION 



In the first series of studies to determine the effect of temperature 

 on spore germination, hanging drop cultures were made on the covers 

 of petri dishes, using distilled water and Czapek's solution, minus the 

 sugar, as media. The spores were taken from a six-days-old bean 

 agar culture. Germination counts were made after 48 hours. The 

 results are given in Table VI. 



TABLE VI 



SPORE GERMINATION OF H. sativitm IN DISTILLED WATER AND IN CZAPEK'S SOLUTION AT 

 VARIOUS TEMPERATURES 



Tempera- 



Distilled water PH 6.7 



Czapek's solution sugar PH 



With the exception of the results obtained at 34 C., a higher 

 percentage of germination was obtained in Czapek's solution than in 

 distilled water. In both cases the optimum occurred at -24. At a 

 temperature of i C. 14 per cent of the spores -germinated in Czapek's 

 solution, while less than i per cent germinated in distilled water. At 

 42 no germination occurred in either case, while at 34 the germina- 

 tion in distilled water was practically the same as at 30, but in Czapek's 

 solution a marked inhibition occurred at the higher temperature. 



After trying various methods for germinating spores, including 

 hanging drops in petri dishes, in van Tieghem cells, films on slides 

 in moist chambers and in moist atmosphere, the most satisfactory 

 method proved to be floating the spores on the surface of a thin layer 

 of a liquid medium in Syracuse watch glasses. In such cultures the 

 spores can be counted directly on the surface under the low power of 

 the microscope. 



In several series, through the different temperature ranges, con- 

 sistently high percentages of germination were obtained at the extreme 

 temperatures when water which had been redistilled over glass was 



