120 MICRO-ORGANISMS AND FERMENTATION. 



majority of cases. However, as yet no evidence has been 

 brought forward that this mould-fungus stands in causal rela- 

 tion to the acid fermentations of milk. Further, it occurs 

 spontaneously in various other liquids, and among these in the 

 saccharine mixtures which are employed in the fermentation 

 industries, and in these it is able to induce a feeble alcoholic 

 fermentation. Thus, according to LANG and FREUDEN REICH, it 

 produces in milk and grape-sugar solutions, in the course 

 of about 10 days, 0'55 per cent., in 5 weeks, 1 per cent, 

 by volume of alcohol ; smaller proportions of alcohol are pro- 

 duced in cane-sugar and maltose solutions. The same authors 

 found that the fungus possesses the faculty of decomposing 

 albuminoid matter to a high degree. Cultures made in milk- 

 sugar nutritive solution develop a powerful odour resembling 

 that of soft cheese (Limburg) ; the Oidium doubtless has some- 

 thing to do with the ripening of this sort of cheese. 



The hyphre, which are often forked, branched, thin-walled 

 and transparent (Fig. 33, 1), form a thick white felt; in the 

 upper part of the filaments transverse septa are formed close 

 together, after which the single cells, filled with very refractive 

 plasma, are detached as conidia (Fig. 33, 3 to 7, 11 to 14, 1*7 

 to 19). When the fungus grows on solid substrata, the hyphae 

 unite and form remarkable conical bodies. As a rule, the 

 conidia, in longitudinal section, are rectangular with rounded 

 corners (Fig. 33, 3, 6, 17 to 19) ; in a growth of this mould- 

 fungus, spherical, roundish, pear-shaped, and quite irregular 

 conidia (Fig. 33, 4, 5, 11 to 14) are, however, almost always 

 present. These organs of multiplication, the only ones known, 

 send out one or more germ-tubes. 



The fungus may occur in beer, especially when poor in 

 alcohol. As the amount of alcohol increases, the conditions for 

 its growth become more unfavourable ; still, neither wort nor 

 beer is exposed to the danger of being attacked to any extent 

 by Oidium, since it is not able to compete in the struggle for 

 existence with the concourse of organisms which at once appear 

 when fermentable liquids are exposed to the atmospheric germs. 



In numerous investigations with top-fermentation yeast, the 

 author has found that it offers a very favourable nutritive material 

 for this fungus, especially when the yeast is in a quiescent 



