190 



MICRO-ORGANISMS AND FERMENTATION. 



in wort with considerable frothing ; it does not, however, 

 ferment maltose. 



The fifth species, which in the form and size of its cells 

 resembles the first, develops a uniform, dull grey film on wort 



FIG. 50. 



Torula, after Hansen : sedimentary forms after one day's cultivation in 

 beer-wort at 25 C. 



and yeast-water at the ordinary room temperature, likewise 

 on lager beer and even on liquids containing as much as 10 

 per cent, of alcohol. It inverts cane-sugar and forms a slight 

 film on the solution. It does not, however, excite any 

 appreciable alcoholic fermentation. 



FIG. 51. 



Torula, after Hansen : sedimentary forms after one day's growth in beer- 

 wort at 25 C. 



A sixth species (Fig. 50), which forms spherical and oval 

 cells, gives a distinct fermentation in beer-wort, yielding as 

 rriuch as 1-3 per cent, by volume of alcohol. It does not 

 ferment maltose solutions. It inverts cane-sugar and in 10 

 per cent, and 15 per cent, solutions of this sugar in yeast- 

 water it yields respectively 5*1 and 6'2 per cent, (volume) of 

 alcohol after fourteen days' cultivation at 25 C. ; the last 

 growth yielded 7 per cent, (volume) of alcohol after two 



