464 SOIL SCIENCE 



5. Potato cylinder: Very scant, glistening, colorless growth sometimes 



occurs on cylinders held in a moist chamber for 30 days, but ordi- 

 narily no growth is secured. 



6. Gelatin stab: Moderate growth at surface and along track of needle 



in 6 days. After 30 days napiform liquefaction is observed. 



7. Beef broth, 5 days : Lightly clouded. 



8. Litmus milk: Reddened in 5 days; neither coagulated nor digested in 



30 days. 



9. Plate cultures. 



Ammonia cellulose agar, 15 days. 



Form : Surface colonies, round or irregularly round ; bottom 

 colonies frequently develop into fern-like growths. 



Size: Surface colonies, 2 to 3 mm.; bottom colonies frequently 

 attain a diameter of 8 to 10 mm. 



Enzymic zone: 1 to 3 mm. in 15 days; 3 to 3.5 mm. in 25 days. 



Elevation : Slightly convex. 



Chromogenesis : Surface colonies show a small white nucleus ; 

 remainder of colony, gray-white; bottom colonies are fluores- 

 cent. 



Internal structure : Coarsely granular. 



Edge: Entire to undulate. 

 Peptone cellulose agar, 15 days. 



Form : Irregularly round. 



Size : Surface colonies 1.5 to 2.5 mm. ; bottom colonies 3 to 5 mm, 

 Enzymic zone: 1.5 to 2 mm. in 15 days; 2.5 to 3 mm. in 30 

 days. 



Elevation : Convex. 



Chromogenesis : White to grayish white. Colonies sometimes 

 show a white nucleus and rim. 



Internal structure: Coarsely granular. 



Edge : Lacerate. 

 Peptone starch agar, 5 days. 



Form : Irregular ; imbedded colonies frequently throw out spine- 

 like growths. 



Size: 1.5 to 2 mm. 



Enzymic zone : 1.5 to 2 mm. in 5 days ; 2.5 to 3.5 mm. in 10 days. 



Elevation : Flat. 



Chromogenesis : White to light grayish white in 5 days ; in 10 

 days the colonies become dark gray. 



Internal structure: Densely granular. 



Edge : Lacerate. 

 Beef agar, 5 days. 



Form : Surface colonies round ; bottom colonies spread out into 

 irregular growths. 



Size : Surface colonies 1.5 to 2 mm. ; bottom colonies 10 to 12 mm. 



Consistency : Very soft in 5 days ; brittle in 10 days. 



Chromogenesis : Semi-transparent, glistening, gray-white ; fre- 

 quently form a small white nucleus, and many colonies are 

 more or less concentric in structure. At an angle of 45° the 

 colonies are fluorescent. 



Internal structure : Granular. 



Edge: Entire to undulate. 



