16 



CIRCULAR KO. 130, BUREAU OF PLANT INDUSTRY. 



Four kinds of media were used: 



Agar A. — The sj^nthetic nitrogen-poor agar designed for the iso- 

 lation of strains of Bacillus tumefacieris^ prepared as follows: Water, 

 1,000 cubic centimeters; sugar, 10 grams; potassium phosphate 

 (monobasic), 1 gram; magnesium sulphate, 0.2 gi'am; agar, 15 

 grams; and congo red, 0.1 gram. 



Agar B. — Beef agar made in accordance with the recommenda- 

 tions of the committee upon standard methods of the American 

 Public Health Association, with the addition of 0.01 gram of congo 

 red to each liter. 



Agar C. — A synthetic agar designed for the isolation of cellulose 

 ferments of the following composition : Precipitated cellulose, 5 

 gi'ams; agar, 10 grams; potassium phosphate (dibasic), 0.5 gram; 

 magnesium sulphate, 0.5 gram; sodium chlorid, 0.5 gram: ammo- 

 nium sulphate, 1 gram; calcium carbonate, 1 gram; tap water, 1.000 

 grams. 



Agar D. — A s3'nthetic agar similar to that described under agar 

 C, except that peptone was substituted for ammonium sulphate. 



Table I shows the action of the various cultures upon these culture 

 media. In no case did subcultures react differently from the original 

 culture. It should be remembered, however, that the writer has pre- 

 viously noted that strains of Bacillus tiimefaciens isolated from dif- 

 ferent host plants show wide differences of absorptive power toward 

 congo red and that the cause of this variation is as yet unexplained. 



Table I. — Action of rarxoun specirs of hortrrin upon coiiffo-rcd media and upon 



cellulose media. 



tCir. 130] 



