8o2 bacteria: their work 



minous crop it has been found beneficial before attempting to 

 grow a particular species of the Leguminosse, to provide that 

 the proper race of nodule-organisms for infection of its roots 

 shall be present in the ground before the seed is sown. This 

 may be effected by spreading over and gently working into the 

 ground soil which has been obtained from a field which has 

 recently carried a good crop of the plant to be grown. 



Under the names ' Nitragin ' and ' Nitrobacterine ' axe sold 

 pure cultures on nutrient gelatine of the various races of nodule- 

 bacteria which are intended to be used for mixing with the seeds 

 of the different leguminous plants before sowing, especially when 

 crops are to be raised on poor virgin soils or on those which 

 have not borne a similar leguminous crop for a great number 

 of years. Instead of appl)dng the cultures to the seed, they may 

 be mixed with a small amount of soil and then subsequently 

 spread over the land. 



Very extensive trials have been made of the effect of ' nitragin ' 

 and ' nitrobacterine ' inoculation, but in only a small proportion 

 of them have the results of its use been distinctly favourable in 

 producing a well-marked increase of crop over non-inoculated 

 sowings. 



Where no difference has been observable between the inocu- 

 lated and non-inoculated plots on the same soil, it is generally 

 found that the roots of the plants on the untreated ground are 

 well supplied with nodules ; apparently the nodule-organisms 

 have been already present in sufficient number in the soil, and 

 the further addition of more by the use of pure cultures has 

 been superfluous. 



On virgin ground an application of soil from a field which 

 has previously borne a leguminous crop rarely fails to produce 

 a good effect, but the use of these artificial cultures in such 

 cases has not been attended with like success. 



More investigation is required in regard to the vitality, con- 

 ditions of growth on different media, time and method of 



