. Carnegie Institution of Washington publication. BACTERIA IN RELATION TO PLANT DISEASES. precautions has led to the statement that certain strict aerobes are able to grow on ordinary media in the absence of oxygen, and that anaerobes are very uncertain in their behavior on standard media. Old pyrogallic acid should be avoided and some preliminary experiments should be made as to the rapidity of the absorption of the oxygen from a given space before the organism is tested. The writer found one brand of pyrogallol which re- moved the oxygen from a small space in six hours, another required abou
. Carnegie Institution of Washington publication. BACTERIA IN RELATION TO PLANT DISEASES. precautions has led to the statement that certain strict aerobes are able to grow on ordinary media in the absence of oxygen, and that anaerobes are very uncertain in their behavior on standard media. Old pyrogallic acid should be avoided and some preliminary experiments should be made as to the rapidity of the absorption of the oxygen from a given space before the organism is tested. The writer found one brand of pyrogallol which re- moved the oxygen from a small space in six hours, another required about eighteen hours, a third required sev- eral days (time enough for a strictly aerobic organism to make a visible growth). Leaks may be detected read- ily by including with the cultures a fermentation-tube, the inclosed arm filled with water except for a small bubble of air. On absorption of the oxygen this bubble expands to a diameter which should remain con- stant if the jar continues air-tight. The gas remaining in receptacles from which the oxygen has been removed by the potash - pyrogallol method is not pure nitrogen, but nitrogen plus a variable small amount of carbon monoxide, which is said to be most abundant when the oxy- gen is absorbed slowly. This small amount of CO is harmless to main- bacteria, but the writer has some reason for suspecting that it is inju-. Flg' rious to others, even if it does not entirely inhibit growth. The writer has found the following contrivance (fig. 55) a very simple one for testing the ability of organisms to grow in nitrogen : A U-tube of thick, clear glass, with arms about 10 to 12 inches long, open at the ends and having a uniform inside diameter of about i inch, serves as the culture-chamber and gas-receptacle. Two short, rimless, cotton-plugged test-tubes containing the media to be tested are inocu- lated and thrust one above the other into one arm of the U-tube, into which is then *Fic. 54.—'Novy jar of large size for Petri dishes
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