General view of culture samples used for an experiment to determine if corn can secure its nitrogen from the air if grown in the presence of nitrogen-fixing bacteria. This experiment was conducted at the U.S. Department of Agriculture's Fixed Nitrogen Research Laboratory located in Washington, D.C. A notation with the photograph notes that no nitrogenous salts were added to any of the bottles. The samples are identified as follows (left to right): Sterile without sucrose; Azotobacter vinelandii without sucrose; Azo. vinelandii with 5 gram sucrose; Azo. vinelandii plus Bacillus cereus with 5 gram sucrose; B. radicicola with 5 gram sucrose; B. radicicola plus B. cereus with 5 gram sucrose.

The Fixed Nitrogen Research Laboratory (F.N.R.L.) was established at American University in 1919 under the directorship of Arthur B. Lamb. Initially part of the War Department, the F.N.R.L. was the successor to several wartime initiatives to develop a secure domestic supply of nitrate compounds necessary for the manufacture of explosives during World War I. With a staff of about 110 individuals, including 35 to 50 chemists, the F.N.R.L. focused on the manufacture, production, and development of products of atmospheric nitrogen, including munitions and fertilizers.