206 ESSENTIALS OF BACTERIOLOGY 



CHAPTER XXII 

 YEASTS AND MOLDS 



IN works on bacteria these true fungi, yeasts and molds, are 

 usually considered. They are so closely related to bacteria, and 

 so often contaminate the culture-media, and are so similar in 

 many respects, that a description is almost a necessity. 



But there are several thousand varieties, and we cannot 

 attempt to describe even all the more important ones. It 

 will answer our purpose to detail a few of the more common 

 kinds, and give the principal features of the different orders. 





Fig. 124. Yeast-cells (x 500) (Frankel and Pfeiffer). 



Saccharomycetes or yeasts increase through budding; the 

 spores are attached to the mother-cell like a tuber on a potato. 



Yeasts are the cause of alcoholic fermentation in the saccha- 

 roses. A description of the most common ones will suffice. 



Saccharomyces Cerevisiae (Torula Cerevisiae). This is 

 the ordinary beer-yeast. 



