102 BACTERIA AND FERMENTATION 



Saccharomyces Ellipsoidus /.—Round, oval, or sausage-shaped cells, single or in 

 chains ; ascospores in twenty-four hours at 25° C. (not above 30° C. , not below 

 4° C). Grown on the sm-face of wort gelatine, a network is produced by which 

 they can be recognised (in eight to twelve days at 33° C). At 13-15° C. a 

 characteristic branching mass is producedi It is an alcoholic ferment as active as 



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Fig. 15. — Diagram of S. cerei)ts«e. Fig. 16.— Diagram of 5. dliji&oidcius. 



S. cerevisice. S. ellipsoideus II. — Round and oval, rarely elongated, a widely dis- 

 tributed yeast, causing " muddiness " in beer and a bitter taste. It is essentially a 

 "low " yeast, and one of the so-called " wild yeasts " injurious to beer. 



Saccharomyces Conglomeratus is a round cell, often united in clusters, and 

 occurring in rotting grapes, and at the commencement of fermentation. 



Saccharomyces Pastorianus I. — Oval or club-shaped cells, occurring in after- 

 fermentation of wine, etc., and producing a bitter taste, unpleasant odour, and 

 turbidity. The spores frequently occur in the air of 

 breweries. 



.iS. Pastor. II. — Elongated cells, possessing an in- 

 vertose ferment. They do not, like /S. factor. I., 

 produce disease in beer. 



S. Pastor. 111. — Oval or elongated cells, producing 

 turbidity in beer. Grown on yeast-water gelatine; 

 the colonies show after sixteen days crenated hairy 

 edges. 



Saccharomyces Apiculatus. — Lemon-shaped cells. 



They give rise to a feeble alcoholic fermentation, and 



produce two kinds of spores— round and oval ; they 



appear at the onset of vinous fermentation, but give 



way later on to S. cerevisice. 



Fig. ll'.— Diagram of S. Saccharomyces Mycoderma. — Oval or elliptical cells, 



pasloriamis. often in branching chains. They form the so-called 



"mould" on fermented liquids, and develop on the 



surface without exciting fermentation. When forced to grow submerged, they 



produce a little alcohol. 



Saccharomyces Exit/uus. — Conical cells, appearing in the after-fermentation of 

 beer. 



Saccharomyces Pyriformis. — Oval cells, converting sugary solutions containing 

 ginger into ginger-beer. 



Saccharomyces lllicis, Hansenii, and Aquifolii produce a small percentage of 

 alcohol. 



2. Acetous Fermentation 



Cause,' Mycoderma aceti; medium, wine and other alcoholic liquids ; result, the 



formation of vinegar. 



If alcohol be diluted with water, and the specific ferment mixed 

 with it and exposed to the air at 22° C, it is rapidly converted into 



