246 THE BLASTOMYCETES 



and 31 i C., most rapidly (in twenty-one hours) at 25 C. ; above 32'5 C. 

 and under 4 C. the development ceases. 



Film Formation. The surface membrane is formed most rapidly 

 (eight to twelve days) at 33 to 34 C., most slowly (sixty to ninety days) 

 at 6 to 7 C. It is always a delicate membrane, and above 38 C. and 

 under 5 C. development ceases. The growth is most characteristic 

 between 13 to 15 C., when it consists of a complicated branching mass 

 of elongated cells or threads, arranged in rows with lateral processes 

 coming off at the point of junction. Secondary branches are formed at 

 the constrictions of the primary branches. 



On Wort Gelatine the colonies present a net-like appearance. It 

 causes as powerful and rapid fermentation as the Saccharomyces 

 Cerevisiae on the various carbohydrates on which that ferment acts. 



SACCHAROMYCES ELLIPSOIDEUS II. 



A ' wild ' or wine fermentation yeast, which gives rise to the 

 muddiness of beer. 



Microscopical Appearances. In young cultures at 1 5 C. the cells 

 are usually somewhat rounded or egg-shaped, while older cultures 

 exhibit longer mycelial rods with forked transverse shoots given off at 

 the joints. 



Spore Formation. The spores are from 2 to 5 ^ in diameter, two 

 to four being found in a single ascus, and may be egg-shaped, slightly 

 irregular, or elongated. They are developed most rapidly at 29 C., 

 most slowly at 8 C. ; above 34 C. and below 4 C. the development 

 ceases, 



Film Formation. It is essentially a low yeast, and the film that 

 forms is very delicate. At 33 to 34 C. it appears in three to four days, 

 but not for five to six months at 3 to 5 C. At 2 and at 40 C. no film 

 is developed. 



SACCHAROMYCES PASTORIANUS. 

 Hansen considers this an impure species, and divides it into three. 



SACCHAROMYCES PASTORIANUS I. (HANSEN). 



A ' wild ' yeast, the spores frequently occurring in the atmosphere 

 of breweries. It gives an unpleasant bitter taste and bad smell 

 to beer. 



Microscopical Appearances. It occurs as elongated ellipsoidal 

 or pear-shaped cells, from which small apical or lateral branches are 

 sometimes given off. 



