174 MICRO-ORGANISMS AND FERMENTATION. 



Microscopic appearance of the cells in the films : 



At all temperatures, the same forms as in the sediment ; 

 at and below 15 C. the cells are only slightly more elongated 

 (Fig. 46). 



In old cultures of films there are colonies of short and 

 long sausage-shaped cells, often with verticillated branches. 



Related to this species are two ellipsoid species, described 

 by Will, and which are also disease-yeasts. One of these, a 

 bottom-fermentation yeast, gives colonies in wort-gelatine, 

 which when young form whether on the surface or embedded 

 in the gelatine a network with large meshes ; afterwards 

 they become denser in the middle, with irregularly-fringed 



FIG. 46. 



Saccharomyces ellipsoideus II. Hansen. Film-forms at 283, 

 after Hansen. 



edges ; sometimes, however, compact colonies with regular 

 outline are formed under the same conditions. The maximum 

 temperature for spore-formation is 39 C. ; at the optimum 

 temperature (34 C.), the first indications of spores are seen 

 after eleven hours. The lower limit for spore-formation is 

 4 to 5 C. The vegetative cells are killed when heated in 

 sterilised wort for half an hour at 70 C. The temperature 

 limits for film-formation are 41 and 4 C. In old films 

 especially are found numerously-branched clusters, consisting 

 of very much elongated cells. This species imparts a rough 

 bitter after-taste to beer and also causes turbidity. 



The second ellipsoid species which was obtained from a 

 beer showing yeast-turbidity, gives colonies in wort-gelatine, 



