Memoirs of the Department of Agriculture in India Studies on the Root Nodule Organism of the Leguminous Plants

Erwin Smith ' on reviewing the subject of nitrogen fixation by the root nodule organisms makes the following observations :- The whole subject of the storage of free nitrogen by this organism in flask cultures and in the plant itself ought to be worked over again carefully by the bacteriologist and the chemist. [...] The present writer had to demonstrate some work in connection with this subject to the students in this laboratory and the opportunity was taken to investigate the question of species by cross-inoculation of the organism from root nodules of one plant on another and the nitrogen-fixing power of the organism independent of the plant under laboratory conditions. [...] In this way all air bubbles present on the surface of the nodule are withdrawn and on admission of air by disconnecting the pump the nodules sink to the bottom of the test-tube and the disinfectant solution is able to act on all portions of the nodule. [...] In those cases however where there was a complete absence of nodules it may be suggested (1) that the nitrogen might be fixed by the organisms in the sand independent of the plant or (2) that the organisms might be present in roots of the plants without formation of nodules due either to lower virulence of the organism or the slow reaction of the plant to the stimulus of the organisms. [...] No such increase is found to have taken place which appears to suggest that the fixation of nitrogen by the organism and the assimilation by the plant go on approximately at the same rate implying the necessity of the removal of the nitrogenous material by the plant before any further nitrogen fixation can take place.