266 FORMATION OF SLIME OR GUM BY RH1Z0B1UM LEGUMINOSARUM, 



coils or chains of bacteria contained within a mucilaginous tube. 

 The presence of slime in the nodule is a fact, and therefore a 

 visible function of the organism within the nodule is the forma- 

 tion of slime. It may have other functions, but of these we are 

 in doubt. 



One of the beliefs which is held at the present time is that 

 after a suppositious fixation of free nitrogen and simultaneous 

 growth of bacteroids, the latter are dissolved in some way and 

 the products of solution are then diffused throughout the plant. 

 In their senescence the nodules certainly atrophy and the nodule 

 tissue must be utilised in the plant economy. But the fixation 

 of nitrogen is manifest before the nodules arrive at this stage. 

 In the growing plant, one would expect the solution of the albu- 

 minous matter of the bacteroids to be actively in progress, much 

 more so than at a later period, but such does not appear to be 

 the case. This was shown in the following experiment. A 

 growing Lupin plant, 12 inches high, had three large nodules on 

 the tap-root. One of these was sterilised and crushed up in a - 2 °/ 

 solution of potassium chloride. A loop of the suspension was 

 smeared over a cover-glass and stained. The bacteria and bacte- 

 roids stained deeply and there were no cells showing a faint 

 staining. The bacterial chromatin was therefore intact, and there 

 was no evidence of the solution of the albuminoids. The film 

 contained approximately 3,000,000 bacteria and bacteroids. A 

 similar loop of the same suspension was smeared over the surface 

 of a plate of maltose-meat-agar and 25 colonies developed. A 

 small nodule growing on one of the lateral rootlets of another 

 plant, 24 inches high, was crushed up in potassium chloride. A 

 small loop of the suspension contained 104,000 deeply staining 

 bacteroidal and bacterial forms. Plates of various saccharine 

 media were smeared with similar loops, and the greatest number 

 of colonies that developed upon a plate was 185. It is clear from 

 this that the great majority of bacteria in these nodules were 

 dead, and yet the staining reaction showed that the albuminoids 

 were not in process of solution. That the microbes fix the 

 ambient nitrogen to build up their albuminoids, which are then 

 dissolved by the plant, is a hypothesis which is therefore untenable. 



