236 



APPLIED BACTERIOLOGY 



sembling the mycelial growth of a mould. The yeasts, 

 however, never give rise to a true mycelium nor to a typical 

 fruit-bearing hyphse. 



The following are the principal varieties of yeasts : 

 Saccharomyces Cerevisise. — This is the typical English 



Fig. 22. — Saccharomyces Cerevisi.e. 



brewery yeast. It grows as rounded or slightly ellipsoidal 

 cells, which give off small cells by budding. The cells are 

 from 8 to 9 ^ in diameter, and occur both singly and in 

 short chains. Spores occur three or four together in a 

 mother-cell 4 to 5 /a in diameter. 



Fig. 23.- 



-Saocharomyces CerevisIjE. (Stages in the develop- 

 ment of ascospores.) 



Saccharomyces EUipsoideus. — This yeast takes the most 

 important part in the fermentation of grape- juice and 

 other spontaneous fermentations. It is usually rounded or 

 ellipsoidal in shape, and it sometimes assumes a sausage 



