38 Journal of Agriculture. [11 Jan., 1909.- 



the seed. These root tubercle bacteria penetrate the young roots and there 

 give rise to tubercular swellings, in which the bacteria are nourished and 

 carry on the assimilation of free nitrogen for the benefit of the plant bearing 

 them. If the root tubercles are not formed, then leguminous plants are as 

 dependent upon supplies of combined nitrogen (nitrates, etc.) as are 

 ordinary plants, so that whenever a leguminous crop, which usually does 

 well on aj particular soil in the absence of nitrates, fails to grow well, the 

 first investigation to make is to pull up some of the plants and see whether 

 the failure is due to the absence or deficiency of root nodules. In this 

 connexion it must be remembered that the use of nitrates as manures tends 

 to suppress the formation of root nodules, since these are then less neces- 

 sary. 



If a leguminous crop fails owing to the non- formation of root tubercles,, 

 it may succeed if the necessary bacteria are supplied to the soil or young 

 seedlings. The root tubercle bacteria appear all to belong to a single 

 species, Bacillns radicicola, but several varieties grow on different plants 

 and these are not mutually interchangeable. Thus, the variety from the 

 pea will infect the bean, but not clover. The soja plant of Japan usually 

 forms no tubercles in Europe although they are abundantly produced in 

 Japan, where the appropriate variety of bacterium occurs. In such cases, 

 the bacterium may be supplied to the soil from a plant of the same kind 

 as that which is to be grown, by crushing its root tubercles to a thin paste 

 with cold water and either spraying the diluted mixture over the land or 

 soaking the seeds in it before planting. A single large root tubercle may- 

 contain several million bacteria, and only one bacterium is needed to start 

 each fresh root tubercle, so that the root tubercles from a small number 

 of plants would be sufficient to infect an acre of soil or several bushels of 

 seeds. Once added to the soil thev appear, however, to die out before; 

 long in the ab.sence of an appropriate host plant, so that the direct appli- 

 cation to the soil usually involves considerable waste and may be quite 

 ineffective. 



CuFtures of nitrogen fixing bacteria, usually termed niiragin* have 

 been placed upon the market and extensively boomed both for direct 

 application to the soil and to the seeds before planting. The.se cultures 

 are only effective when they contain the particular variety of bacterium 

 required, and thev are no better than the material which can be derived' 

 directly from the root nodules. The cultures soon lose their efficacy, and' 

 in many cases have been shown to contain none of the required bacteria 

 at all. 



In fact, in certain cases, unscrupulous persons have taken advantage 

 of a useful scientific discovery to make money by .palming off wotthlcss- 

 rubbish upon farmers eager to adopt scientific methods. It cannot be too 

 strongly emphasized that no heavy outlay for a sujiply of " nitragin " is 

 justified unless the farmer : 



Firstly, is unable to grow certain leguminous crops satisfactorily, 

 even in the presence of lime, potash and phosphoric acid in 

 sufficient amount m tlie soil. 

 Secondly, finds by direct observation that this is due to the non- 

 formation of root tubercles. 



*A very unfortunate term, well adapted for booming a commercial product, 

 but highly confusing to farmers since "nitragin" is the phonetic spelling of the- 

 ( lieinical element, nitrogen, as customarily pronounced, and all farmers now 

 realize the importance of nitrogen in plant nutrition. 



