1. Castle, W. E., J. Heredity, 25, 246 (1934).
2. Paech, K., and Tracey, M. V. (eds.), Modern Methods of Plant Analysis, 3, 272 (Springer-Verlag, Berlin, 1955).
3. Paech, K., and Tracey, M. V. (eds.), Modern Methods of Plant Analysis, 3, 298 (Springer-Verlag, Berlin, 1955).
4. Willimott, S. G., Biochem. J., 22, 1057 (1928).
5. Irish J. Agric. Res. (in the press).