SACCHAROMYCES PASTORIANUS 247 



Spore Formation. The asci are usually elongated or rounded, 

 and may contain two spores or multiples of two up to eight or even 

 more, which vary in size from J '5 up to 5 fj.. They are developed most 

 rapidly (seven to ten days) at 27 '5 C., most slowly (fourteen days) at 

 3 to 4 C. The development ceases at '5 C. and at 31 C. 



Film Formation. The films, which are usually very delicate, are 

 developed most readily (seven to ten days) at from 26 to 28 C., most 

 slowly (five to six months) at from 3 to 5 C. ; development ceases at 34 

 and 2 C. Mycelial-like threads develop freely in the film at from 3 to 

 15 C., and most irregular forms appear. In the older films numerous 

 irregular club, skittle-shaped, and other forms occur. In the younger 

 films the cells are usually smaller and the irregular forms less frequent. 



SACCHAROMYCES PASTORIANUS II. (HANSEN). 



This was also separated from the air of the brewery. It is a 

 feeble top fermentation yeast when growing in beer-wort. It 

 gives rise to neither cloudiness nor to any unpleasant bitter taste. 



Microscopical Appearances. The sedimentary cells are mostly 

 elongated, but may be slightly rounded, varying considerably in size. 

 The cells found in the film are rounded, egg-shaped, or somewhat 

 elongated. 



Spore Formation. The asci are usually elongated, the spores 

 occurring in multiples of two from 2 to 5 p, in diameter. They are 

 developed most rapidly (twenty-seven hours) at 23 C., most slowly 

 (seventeen days) at 3 to 4 C. ; formation ceasing at 29 C. and at '5 C. 

 This yeast secretes an invertase and causes fermentation of all the 

 carbohydrates that are fermented by the other yeasts of this group. 

 In old cultures of the films the cells are small, thread-like, and very 

 irregular in shape. 



SACCHAROMYCES PASTORIANUS III. (HANSEN). 



According to Hansen this yeast is one of the causes of turbidity 

 in beer. 



Microscopical Appearances. The cells are very similar to those 

 of the sedimentary yeast, but at a temperature of from 15 down to 3 C. 

 elongated mycelial-like threads develop, which in old cultures become 

 still more characteristic. In the Saccharomyces Pastorianus I. the 

 mycelial threads are most characteristic at 13 to 15 C., while at 15 to 

 3 C. the cells in Saccharomyces Pastorianus II. are oval and rounded. 



Spore Formation. Similar to the Saccharomyces Pastorianus II. 



