156 DopGE: METHODS OF CULTURE OF ASCOBOLACEAE 
The species of Sordariaceae and Chaetomiaceae that usually 
grow in great abundance with species of Ascobolus, are for some 
reason not often present with A. Winteri on goose dung in this 
region. No spores of any other ascomycete were found on these 
slides. The precautions that are so necessary when pure cultures 
of other Ascobolus species are desired, are of little consequence 
when working with A. Winteri. The molds will be killed off, and 
the number of bacteria introduced with the spores will be much 
reduced by the heating process. Two ovens were used at different 
stages in my studies. One was a sheet-iron drying oven with an 
asbestos-lined shelf on which the cultures were placed. No oven 
of this type can be so arranged as to furnish the same degree of 
heat at all points on the shelf. By regulating a burner so that 
20 minutes were required to raise the temperature of the oven to 
75° C., as shown by a thermometer placed in one corner of the 
oven, and then removing the plates, good results were obtained. 
The plates were often left in the oven to cool, the door being 
opened, or the gas was turned off at 60° C. and the cultures allowed 
to cool in the closed oven. When this last method was employed, 
the spores themselves must have been maintained at temperatures 
between 50°-60° C. for at least 30 minutes. By substituting 4 
burner that would raise the oven to 80° C. in five minutes, the 
per cent of germination was greatly reduced. 
The second oven was porcelain-lined and was found to be less 
satisfactory for these experiments, because the temperature of the 
inclosed air would quickly rise to 100° C. or more while the agar 
medium would still be cool. To determine the temperature t0 
which this oven must be raised in order to bring about germination, 
eight cultures were stacked one on the other in three different tiers- 
It was found that with the oven heated to 100° C. the spores in the 
lowest plates of the three tiers were the only ones that germinated. 
The other plates were then reheated to 65° C. in the sheet-iron 
oven and most of them gave positive results. It is not necessary 
to mention the great number of variations with which these exper 
ments were performed. The size of the Petri dishes, depth of 
agar, and the position of the spores, are all factors which make it 
difficult to determine the exact temperature of the spore in each 
case where a solid medium is used. By quickly opening the ove? 
