ALCOHOLIC FERMENTS. 215 



fermentation yeast. In cultures on gypsum blocks spore- 

 formation begins after 20 hours at 25 C., and in 40 hours not 

 a few free spores may be observed (Fig. 67); at 15 C. the 

 spore-formation takes place in about 40 hours. The oval 

 shape of the spores is characteristic of the species. Spores are 

 also formed in growths in fermenting liquids and on gelatines, 

 and in all cases are soon set free. After long standing, the 

 growth forms a thin film, the cell-forms of which deviate 

 comparatively little from those of the deposited yeast. In 

 plate-cultures the surface colonies formed in the course of two 

 or three days at the room- temperature are film-like, while the 

 embedded colonies exhibit thickly haired, mycelium-like borders. 

 In lactose yeast water (10 per cent), at the room-tem- 

 perature, this species yielded about 1 per cent, by weight of 



FIG. 67. Saccharomyces fragilis. Spore-formation. (HOLM.) 



alcohol in the course of eight days. In two months as much 

 as 4 per cent, by weight of alcohol was produced. At the 

 same time the formation of acid began. In hopped wort 

 (about 11 per cent. Ball.) it yielded at the room temperature 

 about 1 per cent, by weight of alcohol in ten days. 



The optimum temperature for development lies at about 

 30 C. 



According to BAU this species ferments milk-sugar com- 

 pletely, but not melibiose. 



SACCHAROMYCES MINOR (ENGEL). 



The vegetative cells are completely spherical, measuring up 

 to 6 /ot in diameter, and they are united in chains or in groups 

 composed of but few cells (6 to 9). Spore-forming cells are 7 

 to 8 M, containing 2 to 4 spores, 3 /x in diameter. 



