BY H. (iHKIG SMITH. 659 



all who havt" flone bacteriological work with plant tissues, for it 

 is a matter of general experience that many bactei'ia which live 

 in the soil obtain access to the plant. Galippe* found that garlic 

 was the only plant the tissues of which were free from soil 

 bacteria. There should not, howe\er, be so much doubt with 

 regard to the bacteria which cause the formation of the nodule; 

 neither should the morpliologieal and cultural characters oi the 

 organism be so indefinite. Of the bacteria for which nodule- 

 forming jJOwer is claimed, there is distinct evidence in favour of 

 1;wo, viz., Bncterimn. radicicola, P>eijerinck, and Jihizobi\im leyti- 

 minosarum, Frank. The differences between these two organisms 

 are not very great, and it is probable that were the two examined 

 by one bacteriologist they winild be found to be identical. The 

 differences certainly do not justify a difference in name, especially 

 with a microbe which is admitted to be on the borderland between 

 the bacteria, the saccharomycetes and the hyphomycetes. Each 

 investigator considers it to be allied to a different family, and an 

 organism, the characteristics of which ai'e so different from the 

 bacterial type, should have a specific name. The appellation, 

 therefore, given by Frank is to be welcomed, especially as it is 

 becoming more evident that the name bacterium or bacillus must 

 be retained for those organisms that are of a fixed type. Those 

 that grow like the hyphomycetes in some of their stages are now 

 being called by names which indicate a variance from the true 

 type of the fission fungi. 



The circumstance that gives the nodule bacterium its interest 

 is undoubtedly the fact that it either fixes atmospheric nitrogen 

 itself or stimulates the plant to do so. Both Beijerinck and 

 Frank state that pure cultures of their organisms do not assimi- 

 late free nitrogen. Heindrich also showed that the organism 

 grew well on sterile potato, but did not fix nitrogen. On the 

 contrary, Mazef obtained a decided gain of nitrogen in bean 

 sucrose media, containing 1 part of nitrogen and from 100 to 200 

 parts of sucrose. 



* (ialippe, Centralb. fur Bakt. 1 Abt. iii. lOS. 

 t Maze, Annales de 1' lastitut Pasteur xn. 



