614 THE FIXATION OF NITROGEN BY RHIZODIUM LEGUMINOSARUM, 



formed in the cultures ... we have noticed that there is a 

 direct illation between the quantity of nitrogen fixed and the 

 elaboration of this substance in the cultures; its solubility in 

 water, its property of passing through membranes, its absence in 

 the nodules although the bacteria transferred to artificial media 

 elaborate it in 24 hours, have led us to consider it as a nitrogenous 

 material arising from the fixation of the nitrogen and serving as 

 a bond of union between the bacterium and the host-plant." At 

 another place, he shows a gain of nitrogen by a slime-forming race 

 and a loss by a race which was incapable of producing slime. 



Just as my observations upon the structure of Rhizobium* 

 largely corroborate those of Maze, inasmuch as he has depicted 

 it as a compound organism of cocco-bacterial type and I have 

 shown it to be a compound micro-organism of coccus type (leuco- 

 nostoc- or streptococcus-like), so the investigation embodied in 

 this paper upon the fixation of nitrogen confirms and amplifies 

 his observations. The confirmation is the more effective since I 

 have employed synthetic solid media while he used fluid extracts 

 of beans. 



All bacterial slimes are nitrogenous, and because the substance 

 is a slime we are justified, from our knowledge of the effect of 

 albuminoids upon gelatine, etc., in thinking that it contains soluble 

 albuminoids. By the action of heat, the slime is converted into a 

 solution of gum, which in the case of that furnished by the 

 nodule-former is gelatinous, and into a precipitate, probably of 

 coagulated albumen, which encloses the bacterial cells. The gum 

 is nitrogenous, and the nitrogenous matter may be associated 

 with the gum in other than a mechanical manner, for repeated 

 precipitation of the gum from aqueous solution fails to eliminate 

 the nitrogen (p. 271). There is probably nothing in the nature 

 of the albuminous slime to prevent its passing through the porous 

 'cell-walls of the nodular tissue and being utilised as such by the 

 plant. It may, however, be digested by the cell enzymes or even 

 by bacterial autodigestive enzymes before passing from the cell. 



* These Proceedings, p. 295. 



