MICROBIOLOGY OF ALCOHOL AND ALCOHOLIC PRODUCTS. 421 



several varieties will be found in each district. The idea prevalent at one 

 time, that each variety of grapes has its own variety of yeast seems to have 

 been disproved, though there seems to be some basis for the idea that 

 grapes differing very much in composition, varying in acidity and tannin 

 contents, may vary also in the kind of yeast present. Several varieties 

 of S. ellipsoideus may occur on the same grapes. In new grape-growing 

 districts, where wine has never been made, 5. ellipsoideus may be com- 

 pletely absent. 



Besides the true wine yeast, other yeasts usually occur. The com- 

 monest forms are cylindrical cells grouped as S. pasteurianus. These 

 forms are particularly abundant in the newer districts where they may take 

 a notable part in the fermentation. Their presence in large numbers is 

 always undesirable and results in inferior wine. Many other yeasts may 

 occur occasionally and are all more or less harmful. Some have been 

 noted as producing sliminess in the wine. Many of these yeasts produce 

 little or no alcohol and will grow only in the presence of oxygen. 



Pseudo-yeasts. Yeast-like organisms producing no endospores always 

 occur on grapes. Their annual life-cycle and distribution are similar 

 to those of the true yeasts, but some of them are much more abundant 

 than the latter. They live at the expense of the food materials of the must 

 and when allowed to develop cause cloudiness and various defects in the 

 wine. 



The most important and abundant is the apiculate yeast, S. apiculatus . 

 According to Lindner this is a true yeast, producing endospores. The 

 cells of this organism are much smaller than those of S. ellipsoideus and 

 very distinct in form. In pure culture these cells show various forms, 

 ranging from ellipsoidal to pear-shaped (apiculate at one end) and lemon- 

 shaped (apiculate at both ends). These forms represent simply stages of 

 development. The apiculations are the first stage in the formation of 

 daughter cells, the ellipsoidal cells, the newly separated daughter cells, 

 which later produce apiculations and new cells in turn. 



Many varieties of this yeast occur as in the case of S. ellipsoideus. 

 They are widely distributed in nature, occurring on most fruits, and are 

 particularly abundant on acid fruits such as grapes. Apiculate yeast ap- 

 pears on the partially ripe grapes before the true wine yeast and even on 

 ripe grapes is more abundant than the latter. The rate of multi- 

 plication of this yeast is very rapid under favoring conditions and much 

 exceeds that of wine yeast. The first part of the fermentation, especially 



