YEASTS, OR SACCHAROMYCETES 



311 



charine liquid, they germinate and multiply, as usual, by 

 gemmation. Sometimes the growth of the saccharomycetes, 

 especially on solid media, by the growth of the cells in the 

 form of chains, gives rise to a misleading appearance re- 

 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 : 

 Saecharomyces Cerevisise. — This is the typical English 



Fig. 26. — Sacchabomyces Ceebvisi^. 



brewery yeast. It grows as rounded or slightly ellipsoidal 

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



Fig. 27.— Sacchaeomycbs CEliBvisia:. (Stages in the develop- 

 ment of ascospores.) 



from 8 to 9 /i in diameter, and occur both singly and in 

 short chains. Spores occur three or four together in a 

 mother-cell 4 to 5 /^ in diameter. 



