FIXATION OF ATMOSPHERIC NITROGEN 415 



free culture media, dried on cotton and distributed to farmers with a 

 small package of salts from which a culture solution was to be made 

 by the farmer and applied to the seed. This method gave poor results, 

 chiefly because the bacteria could not withstand the drying on cotton. 

 Afterward the cultures were sent in a liquid condition with somewhat 

 more satisfactory results. The dry cotton cultures were exploited 

 for a time by a commercial firm under the name of Nitro-culture, and 

 somewhat similar cultures were placed on the market in England under 

 the name of Nitro-bacterine. Cultures of both kinds, however, were 

 shown to be valueless, both by microbiological and by planting tests. 



Cultures on A gar. Very satisfactory results were secured from the 

 use of pure cultures at the Ontario Agricultural College, Guelph, where 

 Harrison and Barlow, in 1905, originated the method of growing the 

 bacteria on a nitrogen-poor agar medium. By this method, the farmer 

 has simply to apply the bacteria to the seed just before sowing. These 

 cultures, used on all the common legumes, sown in all kinds of soil, 

 gave favorable results in 65 per cent of cases in trials extending over a 

 period of ten years. Similar agar cultures are now prepared by com- 

 mercial firms who have adopted the method of Harrison and Barlow, 

 and also by some of the U. S. Agricultural Experiment Stations. 



Cultures in Soil. *- -Temple has suggested that sterilized soil with 

 the addition of a small amount of leguminous material furnished a 

 very good medium for the propagation of legume bacteria and is suitable 

 for their distribution. 



Attempts have been made to put on the market cultures containing 

 so-called " fertilizing bacteria" good for "all crops," but the tests made 

 with these cultures have thus far failed to bear out the claims made for 

 them. The successful commercial exploitation of cultures containing 

 strong cellulose and protein decomposing organisms, non-symbiotic 

 nitrogen-fixing organisms, strong nitrifying organisms and other useful 

 bacteria is still to be accomplished. 



Importance of Inoculation. Inoculation with pure cultures affords 

 the farmer a rapid, easy, arid cheap method of supplying the bacteria 

 essential for getting a successful stand of any legumes. Failure to secure 

 a benefit from this method of inoculation may usually be attributed to 

 unsuitable soil conditions rather than any inherent failing in the cul- 

 tures used. No method of inoculation will compensate for poor 



* Prepared by Jacob G. Lipman. 



