112 A MANUAL OF BACTERIOLOGY 



4. Draw a conidiophore and spores. 



5. Remove from a Petri dish a bit of agar on which Asper- 

 gillus has been sown two days. Study under the microscope 

 the mycelium it contains. Have the hyphge cross walls ? Do 

 they branch extensively ? Draw a bit of mycelium. 



6. Add some starch to liquid wort and inoculate with 

 Aspergillus oryzae. Test the solution from time to time for 

 sugars with Fehling's solution. 



Exercise 154. Study of Torula 



The genus Torula resembles in most respects that of Saccha- 

 romyces, except that it does not produce spores. The Torulae 

 are widely distributed in nature. They have the power of setting 

 up alcoholic fermentation, but most of them produce by-products 

 which give the solution undesirable odors or flavors. After a 



o 



time they may cause slimy must. 



1. Expose Petri dishes of sterile wort agar to the air. Incu- 

 bate them at 25 C. for two days. 



2. Transfer Torulse from pure cultures or from the Petri 

 dishes to tubes of wort agar, to fermentation tubes of lactose, 

 to tubes of beef broth, and to gypsum blocks. 



3. Make stains and write descriptions of the organisms ; note 

 the differences and similarities between Torulce and yeasts. 

 Some ToruLe produce gas from lactose, but the true yeasts 

 do not. 



Exercise 155. Study of Dematium pullulans 



This fungus is widely distributed in nature, especially upon 

 fruits, and occurs in damp situations in breweries. It is a dele- 

 terious organism in brewing, because it is not only incapable of 

 causing fermentation, but also produces films of growth in the 

 wort and darkens the wort of light-colored beers. 



1. Inoculate tubes of wort agar and flasks of liquid wort 

 with pure cultures of Dematium pullulans. 



2. Find two methods of producing conidia from the hyphre. 

 Find gemmse, or chlamydospores, in the older cultures. Do the 

 conidia resemble yeast in any way ? 



3. Make drawings to illustrate the different phases found. 



