220 THE ROYAL SOCIETY OF CANADA 



The writer has not been able to obtain exact figures from all of 

 the companies in the United States, but has received information 

 from some of them. A conservative estimate, based on the facts 

 supplied, points to the production of about 50,000 cultures a year in 

 the United States. 



These cultures have been examined by a number of the United 

 States Experiment Stations, with good results (4) (5) (6). 



In Europe, a modification of the culture called "Nitragin," first 

 introduced by Nobbe and Hiltner, has been used with varying success. 

 Grabner and von Feilitzen have reported feeble or unsatisfactory 

 results. 



Another culture, named nitro-bacterine, and introduced by 

 Bottomley, was exploited by the Stead publication The Review of 

 Reviews. Conflicting reports of this culture are published. Grandeau 

 and others report total failure with this culture; on the other hand 

 some English reports are more favourable. 



The original medium used for the growth of "Nitro-culture" 

 consisted of commercial maltose, hardwood ashes, and agar; later 

 this was modified and dipotassium phosphate was used instead of 

 the ashes. Both these gave good results; but now and again some 

 variety of Ps. radicicola did not seem to grow well on these media, 

 hence a number of experiments with other media were undertaken. 



