Studies in the Physiology of the Fungi. I. Nitrogen Fixation

The problem of the fixation of free (atmospheric) or molecular nitrogen by the fungi has received attention at the hands of no small number of investigators, yet a careful study of the literature is sufficient to indicate that much further work -with the strictest regards for accurate methods-will be required before the problem is satisfactorily solved. For reasons developed later in this paper, we have felt the desirability of continuing, under different conditions, the investigations begun by one of us some years ago. At the present time there can be no doubt entertained, of course, as to the capacity of the legume tubercle bacteria (Bacillus radicicola vars.) and certain soil forms (notably Azotobacter spp. and Clostridium Pasteurianrum) to fix nitrogen. Here the amounts of nitrogen-increase in relatively small cultures under favorable conditions are so far above any regular experimental errors, and so consistently reported by careful workers, that the simple question of whether or not there is fixation is eliminated. On the other hand, there is much contradictory evidence as to the fact of nitrogen fixation by other bacteria and by the fungi, especially by the moulds and