187 



necessary for the formation of the zygote. If this is the case, then 

 one of the "strains" must be weaker than the other and killed out by 

 the unfavorable conditions, since zygotes were not formed in those 

 cultures that had remained in the one hundred (100) centigrade heat 

 for more than 17^/4 minutes. 



The difference in the resistance between the old and the new zygote 

 material in this set of experiments was not ascertained, as only the new 

 was used. 



When moisture was added as a factor, even when the amount was 

 small, the resistance of the zygotes to the heat declined rapidly. With 

 the amount of moisture ordinarily found in bread it was found to be 

 sufficient to kill the zygotes in less than forty-eight (48) hours, when 

 the temperature was raised to seventy (70) degrees centigrade, the time 

 probably being only a matter of minutes as can be seen from comparing 

 the results of the different experiments as shown in Table III. 



In case there was a large amount of moisture there was a very 

 great dropping off of the power of resistance and also a marked differ- 

 ence in the resistant power of the old and the newly matured zygotes. 

 The rapid decline is when the temperature reaches fifty (50) degrees 

 centigrade. How long the zygotes would resist the temperature of 

 forty-five (45) and forty (40) degrees centigrade was not ascertained. 



From a general survey of all the experiments (See Table III) it 

 will be seen that the zygotes are able to withstand a large amount of 

 heat as long as no moisture is present; but the addition of only a slight 

 amount causes the resistant power to fall off very rapidly. Also the 

 factor of dessication is a very small factor, if any, in the lowering of 

 the vitality of the zygote. On the other hand it is a decided factor in 

 increasing the power of resistance to heat. 



If, then, one wishes to kill niucor, the surest way to do so is to use 

 heat and moisture, not much heat being necessary in this case; while if 

 moisture is not present a high temperature and a long application will 

 be required. 



To Dr. F. M. Andrews of Indiana University, I wish to express my 

 appreciation for the encouragement and assistance given during the 

 Xjrogress of the work. The author also wishes to express her apprecia- 

 tion for the help that Miss Flora Anderson rendered in completing some 

 cf the experiments. 



