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UTILIZATION OF NITROGEN-FIXING POWERS OF LEGUMES. 107 



viously grow. There seems no doubt that the phenomenon is 

 simply one of inoculating the soil with the proper bacteria. 



But soil inoculations with legume earth are troublesome. Soil is 

 bulky and a considerable quantity is needed. To obtain a sufficient 

 amount involves expensive freight charges and the carting of heavy 

 loads. Soil inoculations may also distribute plant diseases and 

 troublesome weeds. If tubercles are produced by bacteria it ought 

 to be possible to obtain the results by inoculating with pure cultures 

 of bacteria. It should be possible to cultivate the bacteria in a 

 laboratory and then to distribute to the farmers the cultures of the 

 organisms. If this could be done it would be a far simpler matter 

 than the use of soil itself. The first attempt to furnish such a culture 

 resulted in an article called Nitragin, which was brought out in 

 Germany. This product was eagerly tried by experimenters and 

 practical farmers; but, although in some cases it seemed to give 

 favorable. results, the success attending its use was so uncertain that 

 it fell into disrepute. Later, various improvements were introduced 

 into the methods of making and distributing the cultures, and a 

 new product, called New Nitragin, has been put forward which 

 gives somewhat better results. This has been tried quite exten- 

 sively in the last three years and the results have been much more 

 positive than in the earlier attempts. Meantime other attempts 

 toward the same end were made in this country. In the labora- 

 tories of the Department of Agriculture extensive experiments were 

 carried out, seeming to show the possibility of increasing the nitro- 

 gen-fixing powers of these bacteria by cultivating them in solutions 

 that are poor in nitrogen. After continued experiments in this line, 

 cultures of the tubercle-producing organisms were sent out for test- 

 ing from the department. These too proved unsatisfactory. They 

 were first sent out upon absorbent cotton, but the bacteria did not 

 live long on the cotton fibers and the farmers were likely to receive 

 cotton containing only dead bacteria. Then they were sent out in a 

 liquid or upon agar but their use has never been very great. 



It thus appears that the use of pure cultures of tubercle organisms 

 for soil inoculation has hitherto not been very successful. But this 

 does not by any means indicate that the methods will not soon be so 



