194 



MICRO-ORGANISMS AND FERMENTATION. 



Microscopic appearance of the cells in the films : 



At 20-28 C. : Almost the same forms as in the sedimentary 

 yeast ; also irregular sausage-shaped cells. 



At 15-3 C. : Mostly oval and round cells. 



In old cultures of films the cells are smaller than in the 

 sediment ; very irregular and sometimes almost thread-like 

 cells are found. 



Streak cultures of this species in gelatine yeast-water give 

 growths with comparatively smooth edges after sixteen days at 

 15 C., and in this respect it also differs from the following 

 species. 



SACCHAROMYCES PASTORIANUS III. (HANSEN). (Figs. 54, 55.) 



Top-fermentation yeast. 



Sedimentary forms grown in wort : Mostly elongated, 

 sausage-shaped, but also large and small, oval and round cells 

 (Fig. 54). 



FIG. 54. Saccharomyces Pastorianus III. (HANSEN). Cell-forms of young sedimentary 

 yeast (after HANSEN). 



It was separated from a bottom-fermentation beer which 

 showed yeast-turbidity, and has been proved by HANSEN to be 

 one of the species which produce this disease. Recent experi- 

 ments of HANSEN show that this disease-yeast possesses another 

 peculiar property ; namely, when the fermenting wort has an 



