The Fungi— Yeasts 373 



formed are approximately equal in size. This type of reproduction 

 is the same as that found with the bacteria. 



True yeasts are characterized by their ability to produce asco- 

 spores— spores within a sac, generally found in pairs or in multiples 

 of two. Each individual spore is capable of producing a new 



I kO»«V>L^l to' *- 







^ 



v^7 



Fig. 65. Asci of Saccharomijces cereviseae. (Courtesy of the 

 Fleischmann Laboratories of Standard Brands, Inc., New York.) 



vegetative cell if allowed to grow under ideal conditions. Bac- 

 teria usually produce but one spore which cannot be considered as 

 a reproductive body in the same sense as an ascospore. The shape 

 and the number of ascospores produced in a cell aid in the identifi- 

 cation of the yeast species. Sexual reproduction by the fusion of 

 two cells has been demonstrated in Schizosaccharomyces. 



Vegetative yeasts are generally killed by an exposure to 60° C. 



