1. Gates, R. R., NATURE, 140, 1013 (1937).
2. Darlington, C. D., and La Cour, L., Ann. Bot. (in the press).
3. Morgan, T. H., Bridges, C. B., and Schultz, J., Carneg. Inst. Yearbook, 32, 298 (1933).
4. Riley, H. P., Cytologia, 7, 131 (1936).
5. Mather, K., Proc. Roy. Soc., B, 124, 97.