6o6 THE NODULE OKGANISM OF THE LKGUMINOSiE 



Beijeriiick could not prove a tixation of nitrogen by pure cultures 

 of the organisms wlien grown in artificial media, but he remarked 

 that it could grow in the presence of a minimum quantity of 

 nitrogenous material provided a sutHcient amount of carbohydrate 

 food was present. At a later date he adA'ised the use of 8-9 per 

 cent, washed gelatine, 2 per cent, sucrose with leguminous plant 

 extract. With regard to carbohydrate food, it is to be noted 

 that there is a considerable quantity of starch in the bacteroidal 

 cells. Bart, radicicola in artificial culture is unable to fix nitrogen 

 directly, but in the presence of carbohydrates it is able to seize 

 the smallest trace of nitrate or ammonium salt and convert it into 

 an albuminoid form. The bacteria separated from the nodules of 

 the different genera of Leguminosie differed in a slight degree, 

 and although this difference prevented the bacteria from one 

 genus producing nodules on the roots of other genera it was not 

 sufficient to make one consider the bacteria as belonging to 

 different families; they could only be considered as varieties of one 

 species. Nobbe considers* that the organism is so influenced by 

 the host plant that it becomes adaptable for existence only in 

 that genus of plant. 



As far as can be gathered,! the luovpliulogicHl and cultural; 

 characters of Bacternim radicicola as described by Beiierinck are; 

 as follows : — 



Small motile swarmei's 0*18 : 0-9/;^, or non-motile rods 1 : 4-5^- 

 the rods show branching forms like the bacteroids of the nodules. 

 No spore formation has been observed, and cultures are killed by 

 exposure to 60°-70^ C. The swarmers are strongly aei-obic. 

 Drying and freezing are without influence. Gelatine-, stai-ch- and 

 cellulose-dissolving or sacchai'ose inserting enzymes are apparently 

 not secreted. On gelatine the colonies grow slowly, are hemi- 

 sphei'ical, whitish, clear or somewhat turlnd; the smaller colonies 



* Stutzer, in Centralblatt fiir Bakteriologie, 2 Abt. i. 68. 



t Lafar, Technisclie Mykologie. 



Kruse, in Flugge's Die Miki'oorganismen. 

 Beiierinck, Centralblatt fiir Bakt. 1 Abt. v. S04, 



