xiv.] YEAST FUNGI. 191 



have the power to split up sugar into alcohol and carbonic 

 acid, but this power is not possessed by all to the same 

 degree. 



(a) Saccharomyces cerevisice (torula cerevisice). This is the 

 ordinary yeast used in the production of beer. The in- 

 dividual full-grown cells vary in diameter from 0*008 to 

 o'oi mm. ; they form beautiful long chains. They produce 

 ascospores. 



(b) Saccharomyces vim is very common in the air, and pro- 

 duces alcoholic fermentation of grape-juice ; it is therefore 

 the proper yeast of wine-production. Its cells are elliptical, 

 slightly smaller than the former ; it forms ascospores. 



(c) Saccharomyces pastorianusis of various kinds (Hansen): 

 in some the cells are about o - oo2 to 0-005 mm - m diameter, 

 in others larger. Some form ascospores, others do not. 

 Most of them can be found in wine-fermentation and in 

 cider- fermentation, but only after the first alcoholic fermen- 

 tation is completed. They are very common in the air. I 

 have sown a Saccharomyces, which was contained in ordinary 

 water, on solid nourishing media (gelatine, and gelatine 

 and broth). It grew up copiously and formed groups of a 

 distinct pink colour. When growing in the depth of the 

 nourishing medium it grew as a colourless torula, no 

 ascospores were formed, multiplication taking place by 

 gemmation only. 1 



(ct) Saccharomyces mycoderma (mycoderma mm). This 

 yeast is found forming the scum or pellicle on the surface of 

 wine, beer, and fermented cabbage (Sauerkraut) ; its cells 

 are oval, about 0*006 mm. long and 0^002 broad. It forms 

 chains ; the ascospores are two or three times larger. It has 

 nothing to do with the alcoholic fermentation, and is not to 



1 Quart. Journ. of Micr. Science, 1883. 



