54 THE SPIRIT OF THE SOIL 



menced " a scientific investigation of the root- 

 nodule organism with a view of making practicable 

 for use in the United States the pure-culture method 

 of inoculation." It was not long before the causes 

 of Nobbe's failures became apparent. The function 

 of the nodule bacteria is to fix free nitrogen from the 

 air. When they were in such an environment as 

 gelatine with combined nitrogen in abundance they 

 became over-fed and lazy, lost their virulence, and 

 no longer had the power to force their way into the 

 roots of leguminous plants and form nodules. The 

 American investigators soon improved on Nobbe's 

 methods. They used a Nitrogen-free medium for 

 cultivating their bacteria, and thus increased the 

 Nitrogen-fixing power of the bacteria. When this 

 stage had been reached the bacteria were dried on 

 cotton-wool and distributed. In the course of the 

 two years, 1903 and 1904, over 12,000 packages 

 were sent out free to farmers in the various districts 

 of the United States, and the report published in 

 January, 1905, showed that 74 per cent, of the trials 

 were successful that is, gave an increase of crop as 

 a result of inoculation. 



These experiments aroused the interest of the 

 Board of Agriculture and Fisheries in this country, 

 and they invited the co-operation of thirteen agri- 

 cultural colleges and experiment stations to try 

 experiments with the American culture. The 

 Journal of the Board of Agriculture for February, 

 1906, however, issued a most pessimistic report as 

 to the results, stating that " the negative results 

 exceed the positive in number, both in plot experi- 



