THE DECOMPOSITION OF CELLULOSE IN SOILS 447 



Chromogenesis : Semi-transparent, grayish white after 15 days ; 



older colonies become yellowish white with a narrow grayish 



white rim. 

 Internal structure : Colony is made up of fine loosely arranged 



granules. The rim of the older colonies is composed of large 

 granules compactly arranged. 

 Edge : Entire. 

 Peptone cellulose agar, 15 days. 



Form : Round or irregularly round. 



Size : 5 to 7 mm. in 15 days ; in 25 days colonies frequently attain 



a diameter of 20 mm. 

 Enzymic zone : 2 mm. in 15 days ; 2.5 to 3.5 mm. in 30 days. 

 Elevation: Saucer shaped. 

 Chromogenesis : Central portion of colony 2 to 3 mm. in diameter 



is semi-transparent, grayish white ; outer portion of colony is 



vitreous. The colony is usually surrounded by a narrow white 



rim. 

 Internal structure : Central portion of colony is granular ; struc- 

 ture of the vitreous portion is indeterminate. 

 Edge : Entire to undulate. 

 Peptone starch agar, 5 days. 



Form : Irregular. Those colonies at the immediate surface are 



round or nearly round, but those beneath the surface and the 



bottom colonies are quite irregular in outline. 

 Size : 2 to 3 mm. 

 Enzymic zone : 3 to 4 mm. 

 Elevation : Flat or very slightly convex. 

 Chromogenesis : The surface colonies show a small white nucleus, 



the remainder of the colony grayish white. The imbedded and 



bottom colonies are grayish to grayish white. 

 Internal structure : Granular. 

 Edge : Lacerate. 

 Beef agar, 5 days. 

 Form : Round. 



Size: Surface colonies 1 to 1.5 mm. ; bottom colonies 2 to 3 mm. 

 Elevation : Convex. 

 Consistency : Colony is soft during the first 10 days, after which 



it becomes brittle. 

 Chromogenesis : By reflected light the colonies are white to light 



grayish white. By transmitted light they are translucent light, 



smoky brown. 

 Structure : Granular. 

 Edge : Entire. 

 Potato agar, 5 days. 

 Form : Round. 



Size: Surface colonics, 1 to 2 mm. ; bottom colonies, 2 to 3 mm. 

 Elevation : Pulvinate. 

 Consistency : Butyrous after 5 days ; somewhat viscous after 10 



days. 

 Chromogenesis : Glistening, yellowish to grayish white. 

 Internal structure: Granular. 

 Edge : Entire. 



