520 Agricultural Journal of Victoria. 



this has to be transported for a large farm, the cost is almost prohibi- 

 tive. There is still another and more serious objection, however, and 

 that is the danger of transmitting plant diseases by this method. 

 Several of the more serious diseases which attack crops are readily 

 conveyed in the soil, and there are numerous cases on record where 

 diseases of leguminous and other crops have been introduced into 

 regions previously entirely free from them through an effort to bring 

 about a soil inoculation of the tubercle-forming organism. Conse- 

 quently, if any safer and cheaper method could be devised for making 

 these germs available, it would be most desirable. 



A few years ago certain German investigators put upon the market 

 a product known as nitragin, which purported to be a pure culture of 

 the root-tubercle organism. These cultures were only adapted to 

 specific crops, for it has been held that each kind of leguminous plant 

 had a special germ better adapted to produce tubercles upon it than 

 any other form, and for this reason it was necessary to use one organ- 

 ism for clover, another for peas, and so on. This preparation, 

 nitragin, has been used with varying success abroad. Some ex})eri- 

 ments seemed to show that it was of the greatest value, while others 

 were complete failures in demonstrating its worth. The failures so 

 far outnumbered the successes, however, that its manufacture has 

 been abandoned, and it can no longer be obtained. A few attempts 

 have been made to use these cultures in this country, and while some 

 very satisfactory results were obtained, the number of failures was 

 even greater than abroad, the varying conditions involved in trans- 

 portation and the length of time which elapsed before the germs 

 could be used being fatal to about 80 per cent, of the material 

 imported. 



Improved Method of Inoculation. 



A little more than a year ago the investigation of these nitrogen- 

 fixing bacteria was begun in the laboratory of plant physiology of the 

 Bureau of Plant Industry, with the hope of discovering some method 

 of artificially inoculating soils which were devoid of the proper organ- 

 isms, and of insuring their producing the desired result. It was soon 

 found that the method in use by the German investigators was not 

 adapted to the life of the organism ; that is to say, the use of rich 

 nitrogenous food material, such as decoctions of the host plant, were 

 not calculated to produce an organism which would fix free nitrogen 

 from the aii . It was found that while the bacteria grew luxuriantly 

 upon such media, they became less and less active, until eventually 

 they lost completely this nitrogen-fixing power. It seemed as though 

 the large amount of nitrates in the media upon which they were 

 grown made it no longer necessary to draw nitrogen from the air, and 

 consequently they deteriorated until they became of no more value 

 than the common soil forms. It has been found, however, that by 

 gradually reducing the amount of nitrogen in the culture medium it 

 is possible to greatly increase the nitrogen-fixing power of these 

 germs, and that by proper manipulation their activity may be in- 



