These assay results are in line with the observations of others (3b•0•12) on the instability of B12b in the presence of certain reducing agents and assay media constituents such as thiamin and ascorbic acid. The apparent differences in microbiological assay attributed to vitamins Bi2a and B12b7 may well be the result of assay methods.Acknowledgments.-The production and isolation of vitamin Bi2b is obviously the result of group effort by many individuals. We are grateful to Dr. G. F. Cartland for active direction of the program, to Dr.

No abstract

These experiments were undertaken to confirm the antibiotic stimulation of plant growth under rigidly controlled conditions, to compare several antibiotics on the basis of their ability to stimulate growth, and to study the mechanism of this stimulatory action. Lemna minor, one of the duckweeds, was used as the test object because it can be rendered aseptic and grown under aseptic conditions easily. Its uniform growth, relatively rapid rate of growth, ability to grow on a chemically defined medium, and small size make it an ideal experimental plant. Not all antibiotics stimulate plant growth. Penicillin G and Bacitracin were outstanding in their ability to stimulate growth under test conditions.In general, most other antibiotics stimulated or inhibited growth according to the concentration tested, the length of the growth period, or the specific conditions of the experiment. The results of this investigation have suggested several hypotheses as to the mechanism of stimulatory action. It is hoped that experiments currently in progress will determine which of these hypotheses is correct. Representativesof most groups

No abstract

No abstract