CHAP, in The absorption of Nitrogen 345 



In the cells of the latter after its development the proto- 

 plasm is found to become frothy and vacuolated, simulating 

 the appearance of a plasmodium. Corpuscles eventually 

 fill the cells, being budded off from the filamentous part 

 of the fungus in great profusion. On the decay of the 

 tubercle later, some of these corpuscles are discharged into 

 the soil, while the rest are dissolved or disappear in the 

 cells. 



Brunchorst investigated the nodules in 1885, and while 

 generally agreeing with Marshall Ward, he concluded the 

 corpuscles to belong to the root and not to the fungus. 

 He called them bacteroids. 



The association of these structures with the process of 

 the fixation of atmospheric nitrogen was made by Hell- 

 riegel and Wilfarth, as already shown. In subsequent 

 researches they confirmed the results already quoted. An 

 instructive series threw a good deal of light on the relations 

 of the two organisms. They traced the growth of the pea 

 seedlings from the onset of germination and noticed that 

 they grew regularly till the reserve food material was 

 exhausted. Then followed a period of rest, followed a little 

 later by a second period of growth. This period varied 

 considerably, in some cases being vigorous, in others only 

 limited. They proved that these variations were caused 

 by variations in the luxuriance of the nodular development. 



Other results from their experiments led them to con- 

 clude that the organism of infection is not the same in 

 different plants, but that probably a specific organism 

 exists for each. They held the view, however, that though 

 the Papilionaceae take atmospheric nitrogen by the aid of 

 theorganism theycanabsorb combined nitrogen, particularly 

 nitrates, from the soil, but they maintained that their 

 development is not normal unless they are aided by the 

 bacterium. Besides the cereals, they obtained negative 

 results with plants of the Chenopodiaceae, Polygonaceae, 



