THE DECOMPOSITION OF CELLULOSE IN SOILS ' 469 



Potato agar: Abundant, grayish white; becomes grayish brown in 10 



days. 

 Peptone starch agar: Abundant, moist, grayish white; in 10 days the 

 growth at the bottom of the slope becomes flesh colored. 



6. Potato cylinder: Moderate, grayish white, leathery growth in 15 days. 



7. Gelatin stab: Good growth at surface and along track of needle in 6 



days; no liquefaction in 30 days. 



8. Beef broth, 5 days : Heavily clouded. 



9. Litmus milk: Blued in 10 days; neither coagulated nor digested in 30 



days. 

 10. Plate cultures. 



Ammonia cellulose agar, 15 days. 



Form : Round or irregularly round. 



Size: 1 to 1.5 mm. 



Enzymic zone: 1 to 2 mm. in 15 days; 3 to 4 mm. in 30 days. 



Elevation: Slightly convex. 



Chromogenesis : Surface colonies opaque white ; bottom colonies 

 semi-transparent grayish white. 



Internal structure: Granular. 



Edge : Erose. 

 Peptone cellulose agar, 15 days. 



Form : Round to irregularly round. 



Size : Surface colonies, 1 to 2 mm. ; bottom colonies 6 to 8 mm. 



Enzymic zone: 1 mm. or less in 15 days; 2 to 3 mm. in 30 days. 



Elevation : Slightly convex. 



Chromogenesis: Surface colonies have a small white nucleus, 

 remainder of colonies grayish white. 



Internal structure: Granular. 



Edge : Entire to undulate. 

 Peptone starch agar, 5 days. 



Form : Irregularly round. 



Size: 2 to 3 mm. 



Enzymic zone: 1.5 to 2 mm. 



Elevation : Slightly convex. 



Consistency : Firm. 



Chromogenesis: White to light grayish white; sometimes shows 

 a small white nucleus. 



Internal structure: Granular. 



Edge : Lacerate. 

 Beef agar, 5 days. 



Form: Surface colonies are round; bottom colonies spread pro- 

 fusely. 



Size : 2 to 3 mm. 



Elevation : Convex. 



Consistency: Soft to butyrous. 



Chromogenesis : Small white nucleus, remainder gray-white. 



Internal structure: Granular. 



Edge : Lacerate. 

 Potato agar, 5 days. 



Form : Round. 



Size : 2 to 5 mm. 



Elevation : Convex. 

 (33) 



