1. The presence of Prof. E. W. Yemm, of the University of Bristol, England, as a Visiting Rockefeller Fellow in the Department of Botany at Cornell University provided the occasion for a re-investigation of the use of glutamine and γ-aminobutyric acid by plants and especially by carrot tissue cultures. The facilities for the experiments employing tissue cultures, with and without coconut milk, under the standardized conditions which are required were already well established in this Department and, with the assistance of Miss K. Mears, these facilities were being used in a variety of investigations supported by the National Cancer Institute of the U.S. Department of Health, Education and Welfare. At the planning stage the role of glutamine had been discussed by one of us (F. C. S.) with Prof. G. Krotkov, of the Department of Biology, Queen's University, Kingston, Ontario, and to his interest in the problem we owe the supply of the 14C-labelled substrates which were used. One of us (R. G. S. B.) from the laboratory at Queen's University undertook the responsibility for the radioactive measurements, leading to the specific activity determinations of the various metabolites studied. The necessary chromatographic separations and the use of quantitative paper chromatography and radioautography were carried out in the Department of Botany at Cornell University, and in this work we wish to acknowledge the help of Dr. J. K. Pollard, Mr.David Margolis, and Mrs. Greenwood, all working with one of us (F. C. S.).
2. Caplin, S. M., and Steward, F. C., Nature, 163, 920 (1949).
3. Steward, F. C., Caplin, S. M., and Millar, F. V., Ann. Bot. (N.S.), 16, 57 (1952).
4. Steward, F. C., and Caplin, S. M., Int. Union Biol. Sci., Ser. B, No. 20, 385 (1955).
5. Shantz, E. M., and Steward, F. C., J. Amer. Chem. Soc., 74, 6133 (1952).