1. Dexter, S. T., Tottingham, W. E., and Graber, L. F., Plant Physiol., 5, 215 (1930).
2. Wit, F., Proc. 6th Int. Grassland Cong., 1607 (1952).
3. Amirshahi, M. C., and Patterson, F. L., Agron. J., 48, 181 (1956).
4. Levitt, J., “Frost Killing and Hardiness of Plants. A Critica Review” (Burgess Pub. Co., Minneapolis, 1941).
5. Greenham, C. G., Aust. J. Biol. Sci., 10, No. 2 (in the press).