372 MICRO-ORGANISMS AND FERMENTATION. 



and in every case 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 sedimentary yeast. In 

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

 or three days at room- temperature are film-like, and fuse 

 together, while the embedded colonies exhibit thickly-haired y 

 mycelial borders. 



In lactose yeast water (10 per cent.), at room temperature^ 

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



Holm found similar species with kidney-shaped spores in. 

 milk and in agave juice. 



In " Sauer " (sour whey, used for the preparation of 

 rennet in the manufacture of Emmenthaler cheese) Freuden- 

 reich and Orla Jensen found a Saccharomyces which pro- 

 duced a pleasant alcoholic odour in cream and formed spores 

 in 23 hours at 25 C. Orla Jensen isolated two species of 

 Saccharomyces from Swiss butter. They ferment maltose and 

 lactose. One forms spores in 24 hours at 25 C., and in three 

 days at 30 C. ; the other only forms spores in six days at 30. 

 In both cases the spore-formation is a scanty one. P. Maze 

 isolated a species directly fermenting lactose from cheese- 

 (Port du Salut), which forms spores in 24 hours at 26 C. 



Zygosaccharomyces Barker! Saccardo et Sydow 



is a yeast species isolated by Barker from ginger. It can be 

 recognised by the fusion of two cells preceding spore-forma- 

 tion. The development can be observed under the microscope in 

 hanging drops of sterile water. Many of the cells will be found 

 to produce beak-like proturberances in twelve hours at 25 C. 



