YEASTS OR SACCHAROMYCETES 237 



form. The cells average about 6 t^ long, singly or united 

 in little branching chains. Two to four spores are found in 

 a mother-cell 3 to 3"5 /u, in diameter. 



Saccharomyces Apiculatus. — This yeast can hardly be said 

 to be a true saccharomyces, as it has not yet been ascer- 

 tained to have any spore formation. It is a very common 

 variety, however, and occurs in ferment-wine and spon- 

 taneously fermented beer; on sweet succulent fruits, such 

 as grapes, cherries, plums, gooseberries, etc. The cells of 

 this yeast have a most characteristic citron shape (hence 

 the name), from the prominences at the end of which the 

 budding takes place. The cells are 6 to 8 /i long, and 

 2 to 3 /u. broad. This yeast invariably appears at the onset 

 of the vinous fermentation of grape-juice, but it soon gives 

 way to the Saccli. ellij^soideus and Sacch. pastorianus. It 

 only gives rise to a very feeble alcoholic fermentation. 



Saccharomyces Pastorianus. — This yeast — of which three 

 varieties, known as I., II. and III., have been isolated by 



/^iK^ 



Fio. 24.— Saccharomyces Pastorianus I. 



Hansen — is very polymorphic in shape. The cells are oval 

 or club-shaped, and also occur as elongated, ellipsoidal, 

 pear-shaped cells. Two to four spores are found in a 

 mother-cell. It takes a part in many spontaneous fermenta- 



