454 



THE MONILLE AND OIDIA. 



injurious to yeast, the cells of which it kills, is probably attri- 

 butable to this powerful action on proteids. On the other hand, 

 Oidium lactis itself offers very strong resistance to external in- 

 fluences. For instance, Lang and Freudenreich report that growth 

 is not appreciably retarded below 60 0. The statements of 

 various authors on the influence of temperature, however, differ 

 considerably, HANSEN (LYIII.) giving 37.5 C. as the maximum 

 and o.50. as the minimum, whereas, according to Weidenbaum (I.) 

 the optimum temperature of vegetation is 20 C. According to 



FIG. 207. Oidium lupuli. 

 a, Aerial hypha, branched and separating- into 

 oidia ; b, end of a branch of same ; c, oidia 

 from the central portion of a wide hypha ; 

 d, isolated oidia before germination. Magn. 

 of a, 100 ; of b-d, 600. (After Lindner.) 



FIG. 208. Oidium pullulans. 

 a, budding yeast-like cells ; b, bud- 

 ding oidial cells ; c, formation of 

 oidia; d, naonilial hypha. Magn. 

 600. (After Lindner.} 



Hansen, the maximum temperature for film formation is 36.5- 

 37.5 0., and the minimum 3 C., which clearly expresses the 

 character of Oidium lactis as a true film-producer. The species 

 also seems to oppose considerable resistance to antiseptics, even 

 a i per cent, solution of corrosive sublimate being insufficient in 

 some cases, whilst i : 1000 of formaldehyde failed, and 2.5 per 

 cent, of carbolic acid required thirty seconds to prove fatal. 

 Though growing well on all nutrient media, the fungus develops 

 preferably on those with an acid reaction. 



Oidium lactis is the representative of a group of species or 

 varieties, a fact demonstrated by the divergent reports on the 

 production of alcohol, the influence of temperature, &c. On the 

 basis of morphological and physiological differences in the appear- 

 ance of the colonies, in the size and shape of the oidia and in the 

 power of peptonisation, M. GIUMM (I.) set up a number of species, 



