OIDIUM LACTIS AND ALLIED SPECIES. 453 



detached, without becoming rounded to any extent, this separation 

 being accompanied for the most purt as observed by Lindner 

 by spasmodic movements of the whole thread. In nearly all cases 

 the separation is so far incomplete that two or more oidia hang 

 together by a corner, and thus form zigzag chains. A filament 

 in this state is particularly characteristic, though even when 

 unbroken the conidial chains present a remarkable appearance 

 owing to the uniformity of shape and dimensions of the members. 

 After their detachment the conidia preserve their rectangular 

 contour for some time, and become rounded only just before 

 germinating. When these isolated oidia are mixed with yeast 

 cells, e.g., those of pressed yeast, they are readily distinguishable 

 from the latter, both by their shape the longitudinal walls are 

 perfectly parallel and contents, these showing up in strong relief 

 and being interspersed with numerous vacuoles and granules. 

 Moreover, the conidia are not merely produced on special hyphse 

 this, indeed, being the exception but the central portion of a 

 hypha may frequently be observed to separate into oidia 

 especially on very moist nutrient media and not infrequently 

 the entire mycelium disintegrates into its component cells. This 

 behaviour brings Oidium lactis and its congeners into close relation 

 with Monilia. Young mycelia, placed in a little water and allowed 

 full access to the air, exhibit in a very marked degree the pheno- 

 menon of cell fusion or "internal conidiation " (see p. 6, vol. ii.). 



The physiology of Oidium lactis has been already commented 

 on in several parts of the present work ; and these remarks may 

 be briefly summarised here. Although, in comparison with 

 Monilia, Oidium may be considered as poor in enzymes, it never- 

 theless possesses a by no means unimportant fermentative activity, 

 which is manifested by a considerable liberation of gas. The 

 quantity of alcohol thus formed is, however, slight, merely traces 

 being produced, according to HANSEN (LVIII.), in beer wort and 

 glucose yeast- water, WEIDENBAUM (I.) giving the amount as 

 0.6 per cent, in a fortnight, and BEEFELD 1.2 per cent, in three 

 months. LANG and FREUDENREICH (I.) found 0.55 per cent, in 

 ten days, or i per cent, in five weeks ; the fermentation, according 

 to these workers, proceeding less vigorously in solutions of 

 saccharose or maltose than in those of glucose or lactose. No 

 invertase could be isolated. Lactic acid (see p. 320, vol. i.) is 

 oxidised by this fungus, the acidity of sour milk being thereby 

 reduced. The presence of proteolytic enzymes is indicated by the 

 liquefaction of gelatin, which is facilitated by an acid reaction, a 

 peculiarity regarded by Weidenbaum as a means of differentiation 

 from Oidium (Monilia) albicans. Lang and Freudenreich also 

 state that a strong smell of soft (Limbunr) cheese is developed in 

 peptonised meat broth containing lactose and maltose, and that a 

 considerable (probably complete) decomposition of casein is effected 

 in sterile milk Henneberg's observation that Oidium lactis is 



