260 SCIENCE PROGRESS. 



| more and more pronounced on the passive contents of the 

 tubercle (how far such a draught on some of the contents 

 has been going during the second stage, we cannot say), 

 and everything incapable of resisting solution and absorp- 

 tion is taken up, leaving the nodule a nearly empty limp 

 collapsed shell, in which such bacteroids as have managed 

 to pass into a sort of resting stage alone remain alive to be 

 scattered in the soil around as the debris of the exhausted 

 nodule rots away. 



It is, at least, certain that the disorganised and absorbed 

 contents thus taken up by the now all-triumphant leguminous 

 plant, are extremely rich in nitrogenous materials ; the 

 question is, can this nitrogen represent any more than the 

 combined nitrogen passed into the cells by the leguminous pla?it 

 itself, and which at most has undergone transformations, not 

 affecting its quantity, in the bodies of the conflicting organ- 

 isms? If so, of course the storage of nitrogen in the nodules 

 would be a mere incident not affecting the question before us. 



Between the years 1888 and 1890 a series of papers by 

 Hellriegel and Wilfarth(23) turned public attention to these 

 leguminous nodules from another side. During the progress 

 of a long series of experiments, valuable in many ways to 

 agricultural science, on the nutrition of cereals andgramineous 

 crops as compared with that of leguminous plants, the above 

 authors were, first, again struck with the great differences in 

 these two classes of plants, as regards their powers of 

 accumulating nitrogenous substances, as already noticed by 

 others ; and were then led to compare the results, as 

 regards gains in nitrogen by the leguminosae, with the 

 prevalence and size of the nodules on their roots. They 

 came to the conclusion, which they abundantly supported by 

 experimental results, that of the various hypotheses afloat to 

 account for the gain in nitrogen shown by leguminous crops 

 none was satisfactory, but that, in some way or other, the 

 presence of the nodules was concerned in the matter — for 

 leguminous plants devoid of nodules, or ill-furnished with 

 them, either lead but a starved existence or die altogether, 

 as do graminese in any case if no source of nitrogen beyond 

 the free nitrogen of the air is at their disposal. 



