185 



Discussion. 



It has been generally thought that zygote material of Mucor would 

 not retain the power of germination for more than one year, but the 

 first experiment demonstrated that they retained this power for at 

 least two years, one year of which they were entirely without moisture. 

 Since this is the case one might expect to find the zygotes in the air for 

 a longer period than that. 



When heat was added as a factor, a remarkable power of resistance 

 was still shown. How long the zygotes would be able to resist the 

 sixty (60) degrees centigrade in a desiccator remains to be seen, as 

 five (5) weeks was the longest period tried. When the temperature 

 was raised to seventy (70) degrees centigrade the old zygotes showed 

 the lesser resistance, not being able to withstand the heat for as long a 

 period as the newly matured ones. 



When the temperature was seventy (70) degrees centigrade the 

 inoculated oven-dried bread resisted to the same extent as those in 

 the desiccator, though when the temperature was sixty (60) degrees 

 centigrade the inoculated oven-dried bread was not able to stand the 

 heat as long as the zygotes in the desiccator. How near it would come 

 to it was not ascertained. The only explanation that the author can 

 give is that the amount of moisture that would be present at sixty (60) 

 degrees centigrade in the oven would be sufficient to be detrimental to 

 the zygotes. 



Those experiments in which the zygotes were placed upon oven- 

 dried bread in an oven at one hundred (100) degrees centigrade would 

 have practically the same degree of desiccation as the three experiments 

 that were placed in the desiccators. In this experiment there is shown 

 the most remarkable case of resistance, twenty-five (25) minutes in 

 this heat not being sufficient to kill the zygotes; but another interesting 

 fact is brought out, that being, that the ability of the mucor to produce 

 zygotes is gone from those cultures remaining in the heat over 17% 

 minutes. 



According to the present understanding of the formation of zygotes, 

 there must be what is termed "two strains." By the term "strain" the 

 author means not different varieties, but what in higher plants would 

 probably be called male and female plants. In other words, there is 

 a differentiation of mycelial threads, the union of the two (2) being 



