204 MICRO-ORGANISMS AND FERMENTATION. 



HANSEN found this species in pressed yeast. Its behaviour 

 towards the sugars is similar to that of the last species, though 

 it develops a greater fermentative activity in solutions of 

 saccharose and dextrose. In wort, it yields only small 

 quantities of alcohol. It does not ferment maltose solutions. 

 It inverts saccharose. 



Experiments of a practical character, carried out by HANSEN, 

 have shown that this species does not produce any disease in 

 beer, even when present in considerable quantities either at 

 the beginning or end of the primary fermentation, or when it 

 is added after the storage of beer. 1 



Some other species examined by HANSEN can likewise 

 ferment saccharose and dextrose, but not maltose and lactose. 



SACCHAROMYCES JOERGENSENII (LASCHE) 



also belongs to the group of the Saccharomycetes, which may be 

 termed Sacch. exiguus. The growth consists of small round and 

 oval cells. The optimum temperature for spore-formation is 

 25 C., the temperature limits being 8 and 30 C. At tempera- 

 tures above 30C. the growth dies rapidly. A true film-forma- 

 tion has not been observed; in old cultures only a very feeble 

 yeast ring forms, and this consisted of round and oval cells. 

 In gelatine it yields colonies which resemble those of low- 

 fermentation brewery yeast. Wort-gelatine is slowly liquefied. 

 The streak-culture is dirty grey in appearance, with smooth 

 edges. This species ferments saccharose and dextrose, but not 

 maltose. When it is mixed with cultivated yeasts and grown 

 in malt-wort, it is consequently suppressed. In " temperance 

 beer," according to LASCHE'S statement, it produces a strong 

 turbidity. 



SACCHAROMYCES MEMBRAN^EFACIENS (HANSEN). 



This peculiar species, which occupies a special place amongst 

 the Saccharomycetes, yields a strongly-developed light grey, 



1 This is of special interest, as Sacch. exiguus was formerly regarded as a 

 disease-producing species. 



