LABORATORY AND TEACHING METHODS 607 



Dextrose Agar. 



Dextrose, grams 10 



Agar, grams 15 



Water, c.c 500 



Nutrient solution (same as for cellulose agar) c.c 500 



Hesse and Niedners Nutrient Agar for Water Bacteria (Smith, p. 196). 



Distilled water, c.c 980. 



Nahrstoff Heyden, an albumose, grams 7.5 



Agar-agar, grams 12.5 



This agar is said to be the most suitable medium for the bacteriologic examina- 

 tion of water. It gives a much larger number of colonies than ordinary agar. It 

 requires no neutralizing. The poured plates are counted according to Dr. Robin 

 on the ninth and tenth day. Chromogens are brilliantly colored (Zeitschr. fur 

 Hygiene, Bd. XXIX: 454-462; see also Amer. Journ. Pharm., LXXVI: 112). 



:4. — Manner of holding test-tubes in making subcultures. {After Williams 

 in Schneider, Pharmaceutical Bacteriology, p. 54.) 



Prune Agar (C. S. Shear and N. E. Stevens, Cultural Character of the Chest- 

 nut Blight Fungus and Its Near Relatives. Circular No. 131, U. S. Bureau of 

 Plant Industry). — Take four ordinary prunes and add i liter of water. Boil over 

 an open flame for one hour, being careful not to break the skin of the prunes. Strain 

 through gauze, make up to the original amount with distilled water and add 2 per 

 cent, of agar. Steam for three-quarters of an hour, filter and tube. Autoclave for 

 fifteen minutes at ii5°C. (Fig. 213). 



Media for Mine Fungi (Dr. Caroline Rumbold). 



1. Pure gelatin 10 per cent., 20 per cent. Bausch and Lomb imported seal gelatin. 



2. 6 per cent, gelatin, 2.5 per cent. Liebig's extract, i per cent, citric acid. Cox's 

 gelatin can also be used. This was more successful than the golden seal gelatin. 

 This with i per cent, citric acid solidified. 



Laboratory Work. — Inoculate any or all of the several nutrient agars with several 

 of the stock cultures of fungi. Note the rate of growth and dififerential character of 

 the growth on the different media (Fig 214). 



