THE DECOMPOSITION OF CELLULOSE IN SOILS 449 



Peptone cellulose agar, 15 days. 



Form : Surface colonies round ; bottom colonics irregularly round. 

 Size: Surface colonies, 1 to 2 mm.; bottom colonies 12 to 15 mm, 

 Enzymic zone: Surface colonies, 2 to 2.5 mm.; bottom colonies, 



1 mm. or less. 

 Elevation : Flat or very slightly convex. 

 Chromogenesis : Central portion of colony opaque white ; outer 



portion, semi-transparent grayish white. Brownish rings 



sometimes apparent. 

 Internal structure: Central portion of colony coarsely granular, 



remainder of colony finely granular. 

 Edge : Usually entire, but some colonies throw out a thin film-like 



growth beyond the enzymic zone forming ear-like lobes. 

 Beef agar, 5 days. 



Form: Round or irregularly round. 



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



spread over a large part of the plate. 

 Elevation : Decidedly convex. 



Consistency: Soft; old colonies become sHghtly viscous. 

 Chromogenesis: White or light grayish white; bottom colonies 



frequently somewhat fluorescent. 

 Internal structure : Granular. 

 Edge: Entire to undulate. 

 Potato agar, 5 days. 

 Form : Round. 

 Size : Surface colonies 2 to 3 mm. ; bottom colonies may attain a 



diameter of 10 mm. 

 Elevation : Distinctly convex ; old colonies become somewhat 



umbilicate. 

 Consistency : Soft 

 Chromogenesis: Glistening grayish white; some colonies show a 



white nucleus and rim. 

 Internal structure : Granular ; nucleus is more coarsely granular 



than remainder of colony. 

 Edge : Entire. 



11. Filter paper broths, 15 days. The paper is reduced to a disintegrated 



fibrous mass which retains its pure white color. The destruction takes 

 place at about the same rate with ammonium sulphate, potassium 

 nitrate or peptone as the source of nitrogen. With casein as a 

 source of nitrogen the destruction of the paper is less rapid, 



III. Biochemical Features. 



12. Dunham's solution, 10 days. No ammonia produced; no nitrite pro- 



duced. 



13. Starch nitrate solution, 10 days. No ammonia produced; nitrite pro- 



duced. 



14. Peptone nitrite solution, 10 days. Indol produced. 



15. Carbohydrate broths, 12 days. No gas produced. Per cent of acidity 



(Fuller's Scale) with: Dextrose, 1.80; Lactose, .85; Saccharose, 

 1.30; Maltose, 1.30; Glycerine, .45; Mannite, .00; Starch, 1.35. 



