386 



MOULDS AND YEASTS 



FIG. 53 Oospora. lactis, Sacc. 

 (Oictium lactis, Fres.). 



resembling the conidia of the fungus, except that the 

 ends preserve their rectangular outline for some time, 



becoming rounded only when 

 they begin to germinate (Fig. 



5)- 



The fertile hyphae bear con- 

 idia, some of which are globose 

 or oval, others longer and more 

 or less cylindrical from 1 8 to 

 2 1 (L long and 5 to 8 & broad. 

 Oospora lactis grows well 

 upon acid media, especially 

 those containing lactic acid, 

 which it oxidizes readily. 



Acid gelatine is liquefied and the casein of milk is pep- 

 tonized by it : the optimum temperature for its growth 

 is about 20 C. 



Ex. 170. Procure a piece of rancid butter, or keep a piece of 

 butter on damp blotting-paper in a Petri dish for three or four 

 weeks. 



From the outside of either scrape off a small portion : work it 

 gently in a mortar with a little water and inoculate a tube of 

 melted lactose gelatine with a drop of the mixture. Pour into a 

 Petri dish and incubate at 20 C. 



Examine any white stellate colonies for Oospora lactis. 



When found, make drawings of the conidia and hyphae. 



Inoculate a tube of sterile milk with the fungus and incubate 

 at 20 for two days : examine a drop of the milk for the fungus 

 and note the rectangular outline of pieces of the hyphae. 



Stain some with weak gentian violet. 



The fungus may sometimes be obtained on cream when it is 

 left in a beaker undisturbed for a time. 



Ex. 171. Grow Oospora lactis in sterile litmus milk. 



