THE PRINCIPAL YEASTS 565 



8. cerevisice I. and II. These are bottom fermentation forms in 

 use at the Old Carlsberg Brewery ; the cells of No. II. are rounder 

 and slightly larger than those of No. I., and ascospore formation is 

 more abundant. 



There is also a top fermentation form described by Hansen 

 (8. cerevisice I. top), which is the yeast employed in the breweries 

 of London and Edinburgh. 



The yeasts of the cerevisice group can invert cane sugar, select 

 dextrose from Isevulose, and ferment maltose, but they cannot 

 ferment lactose, nor decompose m alto -dextrin. 



PASTORIANUS GROUP. These are wild yeasts. The cells are 

 elongated or sausage- shaped, and six or eight ascospores are 

 produced in a cell. 



8. pastorianus I. A bottom fermentation yeast producing a 

 bitter taste in beer. 



8. pastorianus II. A feeble top fermentation form. Surface 

 cultures on yeast-water gelatin have smooth edges, which distin- 

 guishes it from the next species. 



8. pastorianus III. A top fermentation form producing 

 turbidity in beer. Surface cultures on yeast-water gelatin have 

 woolly margins. 



ELLIPSOIDEUS GROUP. These are wild yeasts. The cells are 

 usually ovoid, or pear-shaped, sometimes round, rarely elongated. 

 Five or six ascospores are produced in a cell. 

 8. ellipsoideus I. A bottom fermentation yeast occurring on 

 ripe grapes. 



8. ellipsoideus II. A bottom fermentation yeast causing 

 turbidity in beer. 



Both the pastorianus and ellipsoideus groups resemble the 

 cerevisice group in their chemical actions, but they are able in 

 addition to decompose malto -dextrin. 



8. anomalus is a yeast forming small ovoid cells. It is curious 

 in that the spores are hemispheres with a projecting rim at the 

 base like a bowler hat. 



Another point in the identification of species of yeasts is the 

 period of formation of films. If the yeast is grown in wort with 

 free access of air and is undisturbed, e.g. in a beaker capped with 

 filter-paper, after a varying period a film composed of a zoogloeal 

 mass of cells appears on the surface. 



If yeast, or disintegrated yeast-cells, be injected into animals, 



