1 82 Nitrogen Fixation by Yeasts 



out some experiments on the fixation of nitrogen by fungi similar 

 to those with which Duggar and Knudson worked and it is hoped 

 that the results may be available for publication in the near future. 

 The objections of Czapek to the work of Puriewitsch and Saida 

 would not seem to be valid in view of the writer's experiments, 

 since the method of nitrogen determination employed as above 

 described has been carefully tested in my laboratory, allows of 

 a close agreement between duplicate series of determinations, and 

 has given most satisfactory results in other phases of microbio- 

 logical work. 



SUMMARY OF RESULTS. 



1. Of eighteen organisms, including yeasts, pseudo yeasts and 

 molds, tested nearly all show a more or less pronounced power of 

 fixing atmospheric nitrogen. 



2. Tap water sugar solutions are better suited for nitrogen 

 fixation by the organisms tested than distilled water solutions. 



3. Mannite and lactose solutions are far superior to dextrose, 

 saccharose and maltose solutions for these organisms in distilled 

 water, but dextrose is the best in tap water solutions. Maltose 

 is the most unsatisfactory. 



4. The highest amount of nitrogen fixed was 2.94 mg. per gram 

 of mannite by pseudo yeast Tulare no. 46b in distilled water man- 

 nite solution. 



5. The results of other investigators with reference to the nitro- 

 gen fixing powers of Aspergillus niger and Penicillium glaucum 

 are confirmed. 



6. Botrytis cinerea, a parasitic fungus, has been found for the 

 first time, so far as the writer is aware, to possess a nitrogen fix- 

 ing power. 



My thanks are due my former assistant, Mr. J. A. McKeen, 

 for valuable assistance in making the nitrogen determinations. 



