SACCH. CEREVISLE. 



327 



At 15 to 6 C. (Fig. 62). The greater number of the cells 

 resemble the original cells ; isolated abnormal forms occur. 



In old cultures of films all forms occur, including extremely 

 elongated mycelial cells (Fig. 63). 



The temperature limits for budding in wort are 40 C. 

 and 1 to 3 C. The species develops invertase and maltase ; 

 it ferments saccharose, maltose, and dextrose, but not lactose. 

 It produces a vigorous fermentation in beer- wort. 



The first series of pure top-fermentation species were pre- 

 pared by the author in 1884 from material collected in many 



Fig. 61. Saccharomyces cerevisice I. (Hansen). Cell-forms of young sedimentary yeast 



(after Hansen). 



Fig. (V.Saccharomyces cerevisice I. (Hansen). Film-forms at 15 to 6" C. (after Hansen). 



European countries, with the object of introducing such pure, 

 selected types, developed from single cells, into practice. It 

 was soon seen that the typical differences between the species 

 were much more pronounced than is the case with low-fermen- 

 tation yeast. It was found that one group of the species used 

 in breweries had an extraordinarily weak fermentative activity. 

 The fermentation ceased, under the conditions existing in the 

 breweries, when 1 to 2 per cent, of alcohol had been formed in 

 beer-wort ; the main mass of the yeast usually spread out over 

 the surface of the liquid to form a coherent layer. 



