326 MICRO-ORGANISMS AND FERMENTATION. 



Saccharomyces cerevisiae or Saccharomyces cerevisiae L 



Hansen. 



This species, described in 1883, is an old English top- 

 fermentation yeast which is in use in London and Edinburgh 

 breweries. 



The young growth of sedimentary yeast developed in wort 

 consists essentially of large round and oval cells ; truly 

 elongated cells do not occur under these conditions. 



Ascospore-formation (Figs. 52 to 54, and 58, 1) : * 

 At 37-5 C. no ascospores are developed. 



36-37 the first indications are seen after 29 hours. 

 35 25 



33-5 ,, ,, 23 ,, 



30 20 



25 23 



23 ,, ,, 27 ,, 



17-5 50 



16-5 ,, ,, 65 ,, 



11-12 ;, 10 days. 



9 no ascospores are developed. 



Wall of spores very distinct. Size of spores 2-5 to 6 yu. 

 Film-formation : 



At 38 C. no film-formation occurs. 

 33-34 feebly-developed film specks 



are seen after . .9-18 days. 

 26-28 7-11 



20-22 7-10 



13-15 15-30 | 



6- 7 2- 3 months.] 



5 no film-formation occurs. 



Microscopical appearance of the cells in the films : 

 At 20 to 34 C. ; colonies frequent ; sausage-shaped and 

 curiously formed cells occur. < 



* The preparatory treatment of a Saccharomyces species for these investi- 

 gations must be made in the following manner : After the cells have been culti- 

 vated for some time in ordinary wort (14 Ball.) at the ordinary room temperature, 

 the vigorous young cells obtained are introduced into fresh wort, in which they 

 are allowed to develop for about twenty-four hours at 25-27 C. This growth 

 is used for the gypsum-block culture. 





