SACCHAROMYCES. 355 



Film-formation : 



At 40 C. no film-formation occurs. 

 36-38 feebly-developed film-specks 



are seen after . 8-12 days. 

 33-34 3- 4 



26-28 4- 5 



20-22 4- 6 



13-15 8-10 \ (Fig. 77.) 



6-7 1-2 months. 



3-5 ,, ,,5-6 



2- 3 no film-formation occurs. 



Microscopic appearance of the cells in the films : 



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



a,nd below 15 C., the cells are only slightly more elongated 



<Fig. 77). 



Saccharomyces Willianus Saccardo 



is a disease yeast described by Will as having elliptical cells. 

 In the old films strongly branched budding-colonies occur 

 consisting of very long cells. The maximum temperature 

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

 (34 C.) the first traces of spores occur in eleven hours. The 

 lowest limit for spore-formation is 4 to 5 C. The limits for 

 film-formation are 41 and 4 C. The vegetative cells are 

 killed when heated in sterilised wort for half-an-hour at 70 C. 

 It forms colonies in wort gelatine, which in the young state 

 (both embedded and on the surface) form a network of wide 

 mesh. They afterwards become denser in the middle with 

 irregularly fringed edges. Sometimes, however, under the 

 same conditions, compact colonies with regular outline are 

 formed. 



This species imparts a peculiar sweet taste to beer, followed 

 by a rough bitter after- taste, even in presence of very minute 

 quantities (0-1 per cent.) in the pitching yeast. The beer is 

 often rendered turbid by this wild yeast after two months 

 at 4 to 5 C. This yeast has a strong fermenting and 

 propagating power, and is very dangerous for beer. 



