i6 4 AIDS TO BACTERIOLOGY 



spontaneous fermentations, and in the vinous fermenta- 

 tion usually succeed 8. apiculatus. They are classed as 

 ' wild ' yeasts, the spores of which frequently occur in 

 the atmosphere of breweries. 



8. pastorianus /. is a ' bottom ' form, and causes a 

 disagreeable smell and a strong, bitter taste in beer. 



& pastorianus II. is a feeble ' top ' form, and of no 

 particular importance. 



S. pastorianus III. is a top form, and is a dangerous 

 disease yeast, causing yeast turbidity. 



Saccharomyces Apiculatus. This very common yeast 

 can scarcely be termed a true saccharomyces, as no spore 

 formation has yet been demonstrated. It occurs in 

 wine fermentations and spontaneously fermented beer; 

 on sweet succulent fruits, such as grapes, cherries, plums, 

 gooseberries, etc. The cells, which are 6 /a to 8 ^ long 

 and 2 /j, to 3jbi broad, have a most characteristic citron 

 shap3 (hence the name), from the prominences at the end 

 of which the budding takes place. It invariably appears 

 at the onset of the vinous fermentation of grape-juice, 

 but soon gives way to the S. ellipsoideus and 8. pastorianus. 

 It is a bottom yeast form, only gives rise to a very feeble 

 alcoholic fermentation, and is incapable of fermenting 

 cane-sugar and maltose. 



Saccharomyces Mycoderma (Myeoderma Cerevisise). 

 The cells are oval, elliptical, or cylindrical, 6^ to 1 ja long 

 and 2/z to 3/bi thick, united in freely-branching chains. It 

 forms the skin, or ' mould,' on the surface of fermented 

 liquids, without, however, exciting fermentation. When 

 forced to grow submerged in a saccharine liquid, it gives 

 rise to a small quantity of alcohol, but development is 

 feeble. In liquids already containing alcohol it produces 

 ethyl acetate. 



Saccharomyces Exiguus. Conical or top-shaped cells, 

 5 fju long, and reaching 2*5 //. in thickness, in slightly 

 branching colonies. There are two or three spores in 

 a row in each mother cell, but spore formation is scanty, 

 and film formation does not occur. It is incapable of 

 fermenting maltose. This yeast is often present in the 

 after-fermentation of beer. 



Saccharomyces Marxianus. A yeast found on grapes. 

 The cells are small, oval, or sausage-shaped, and form more 

 or less kidney-shaped spores, the optimum development 



