LABORATORY AND TEACHING METHODS 595 



Claussen's Ctdture Medium for Pyronema confiuens. — See Kuster, Ernst: 

 Kultur der Mikroorganismeii, p. 152. Claussen places in a Petri dish a small glass 

 vessel and fills this to the rim with agar of the following formula: 



Per cent. 



Agar 2 . 000 



InuUn puriss 2. 000 



KHzPOi 0.050 



NH4N03 0.050 



MgSOi o 020 



Fea(P0i)2 o.ooi 



H2O 95.000 



The outer free margin of the Petri dish is filled with inulin-free agar to a similar 

 height as in the inner glass dish. In the middle one, spores of Pyronema are sown. 

 After a few days the fungus will fruit on the inulin-free substratum. 



Tubeufs Culture Medium for Dry-rot Fungus. — See KtJSTER, Ernst: Kultur 

 der Mikrobrganismen, p. 154. 



Grams 



Ammonium nitrate 10 



Potassium phosphate 5 



Magnesium sulphate. . , i 



Lactic acid 2 



Water 1000 c.c. 



Laboratory Work. — Each member of the class should make up at least three of 

 the above, culture media. In order to save material, if the class consists of four to 

 six students, the fuU amount of materials can be used and the final amount of liquid 

 divided into four to six parts for the experiments of each member of the class with 

 all of the media made according to the above formulse. AVhere the class is smaller 

 than four students, then one-half, or one-fourth of the materials should be used, 

 as some of them are expensive chemicals. 



Inoculate all of the culture solutions with yeast obtained from a cake of Fleish- 

 man's compressed yeast. Sterilize the needle and add some of the yeast on the end 

 of the sterile needle. Study and note the growth of the yeast in the several culture 

 media inoculated. Bacteria can also be used. 



Fermenting Power of Different Yeasts. — Take a series of fermentation tubes and 

 fill to the tops of the upright long branch with any of the liquid culture media used 

 especially for yeasts. Inoculate one with dried yeast, one with brewer's yeast, 

 one with compressed yeast, one with baker's yeast and others with several of the 

 yeasts kept in pure culture, and plug the open end with cotton. Compare the de- 

 pression of the upright column of liquid in the different fermentation tubes in order 

 to determine the relative amount of gas formed. 



