316 MICRO-ORGANISMS AND FERMENTATION. 



A. TRUE SACCHAROMYCETES. 



1st Group. 



The cells immediately form sedimentary yeast in saccharine 

 nutritive liquids, and only at a much later stage form a film 

 with slimy growth and without inclusion of air. Spores smooth 

 round, or oval, with one or two membranes. Germination by 

 budding or by the formation of germinal tubes (promycelium). 

 All, or at any rate the greater number, of this group bring 

 about alcoholic fermentation. 



GENUS I. Saccharomyces Meyen. 



The spores provided with one membrane germinate by 

 budding. In addition to formation of the yeast cells a few 

 give mycelium with distinct transverse walls. 



(To this genus belong the culture yeasts and the great 

 majority of wild yeasts.) 



GENUS II. Zygosaccharomyces Barker. 



Distinguished by the copulation of cells. In other respects 

 identical with the preceding genus. 



GENUS III. Saccharomycodes E. C. Hansen. 



By germination of the spores, possessing one membrane, 

 form a promycelium. From these, as well as from the vege- 

 tative cells, budding takes place with incomplete separation. 

 Formation of mycelium with distinct transverse walls. 



GENUS IV. Saccharomycopsis Schionning. 



The spores possess two membranes, otherwise the characters, 

 o far as they are known, are identical with those of Saccharo- 

 myces. 



2nd Group. 



The cells immediately form a film in saccharine nutritive 

 liquid, which is dry and opaque en account of the inclusion of 

 air, and can readily be distinguished from the film-formation 

 of the first group. The spores are hemispherical, angular. 



