SACCHAROMYCES CEREVISIAE 231 



takes place at both ends of the cells. The optimum temperature for 

 budding is from 35 to 37 C. A scum formation has not been ob- 

 served. Sporulation has been observed in the excrements of rabbits. 

 Ascospores are formed to the number of one to four in each asc. They 

 are oval, elongated and, according to Wilhelmi, are surrounded with a 

 double membrane, an exosporium and an endosporium. Wilhelmi has 

 been able to cultivate Saccharomyces guttulatus in various artificial 

 media. It grew especially well in glycerol gelatin to which tartaric 

 acid and dextrose had been added. It inverts saccharose and ferments 

 dextrose. Casagrandi and Buscalioni have noted its pathogenic proper- 

 ties on subcutaneous injections into guinea pigs, rats and rabbits. 



Genus IX. Saccharomyces. Meyen 



Ascospores in a single membrane germinating by budding. Some- 

 times a mycelium is produced with transverse walls. 



A. First Sub-group 



Yeasts fermenting saccharose, dextrose and maltose but having no 

 action on lactose. 



SACCHAROMYCES CEREVISIAE. Hansen 1 



Syn. s. CEREVISIAE i, Hansen. s. CEREVISIAE, Meyen. TORULA 

 CEREVISIAE, Turpin. CRYPTOCOCCUS FERMENTUM, Kutzing. 

 HORMISCUM CEREVISIAE, Bail. s. CEREVISIAE, Rees 



This species is a top yeast which was found by Hansen in 

 breweries of London and Edinburgh and 

 has been used for a long time in the 

 making of beer. Hansen gave it the 

 name S. cerevisiae because it resembled 

 the yeast described under the same 

 name by Rees and Meyen. Young cells 

 in the sediment in beer wort are large arid 

 either round or oval. Elongated cells 

 are not observed under these condi- Fig. 98. Ascs of S. cerevisiae 

 tions. (Fig. 2.) The temperature limits (after Hansen). 



for budding in beer wort are: minimum, 1-3 C.; maximum, 40 C. 



1 'Hansen, E. C. Recherches sur la morphologie et la physiologic des alcoo- 

 liques ferments. II, Les ascospores chez le genre Saccharomyces. Ill, Sur la 

 Torula de M. Pasteur. IV, Maladies prorogues dans la biere par les ferments 

 alcooliques. Comp. rend, du lab. de Carlsberg, Vol. 1, Book 2, 1883; Vol. 2, 

 Book 4; Vol. 5, Book 2, 1909. 



