256 '^^® Royal Society, London. 



Berichte gelehrter Gesellschaften. 



The Royal Society, London, 8/12. 1898. 



Dawson, Maria. Communieated by Professor H. Marschall 

 "W a r d. 



„Nitragiu and the nodule s of Leguminous plants. 



(Abstract.) 



A study of the nodules found upon the roots of legumiuous 

 plants has led the author to an nnhesitating contirmation of the 

 parasitic nature of both the filaments and the bacteroids con- 

 tained in these organs. The filaments, it was found, have no 

 such constant relation to the nucleus of the cells, as was re- 

 presented by Beijerinck in 1888. By plasmolysis of the root- 

 hairs, the infection tube is shown to have grown into the hair, 

 and not to correspond with the primordial utricle of the hair 

 a result which proves that Frank was mistaken in regarding the 

 tube as formed from the contents of the hair mingled with fungal 

 protoplasm. By staining with aniline blue and orseillin these 

 tubes and the filaments in the cells were shown to consist of 

 Strands of straight rodlets, lying parcillel to the longer axis of 

 the filament, and embedded in a colourles matrix. This matrix 

 does not consist of cellulose, chitin, or any form of slime. The 

 swellings upon the filaments occur at places Avhere the rodlets 

 have become heaped up, and at such places the filaments 

 eventually burst, liberating the rodlets, whilst they themselves 

 remain as pointed portions, directed towards each other in the 

 cells. After liberation from the filaments, the rodlets become 

 transformed into X, V, and Y-shaped bacteroids. This variety 

 of shape does not occur Avhen these organisms are cultivated 

 ousside the plant on a solid medium, but in liquid pea extract, 

 the change trom straight rodlets to „bacteroids" occurs in a few 

 days. By cultivating these organisms in drop cultures under 

 constant Observation with high powers, these rodlets are seen to 

 multiply by division into equal, or sometimes slightly unequal, 

 halves. By this method the author hopes also to determine whether 

 the change in shape arises from fusion of two or more individuals 

 or by branching. Their multiplication by division leads to the 

 conclusion that these organisms are members of the Schizomycetes ; 

 whether or not they are true Bacteria luust, however, still be 

 undecided, until the final stage in their life history has been 

 fully followed. 



The X, V, or Y-shaped bacteroid, when once formed appears 

 to be incapable of further growth. These organisms are aerobic 

 in character, their power of fixing atmospheric nitrogen is to be 

 tested in connection with their growth on silicic acid gelatine. 

 Commercial „Nitragin" consists of niinute micrococcus-like bodies. 

 all straight and immobile. They multiply rapidly on gelatine 



