1. Braun-Blanquet, J., Fuller, G. D., and Conard, H. S., “Plant Sociology”; published by Fuller, G. D., and Conard, H. S. (1932).
2. Porter, L. K., and Thorne, D. W., Soil Sci., 79, 373 (1955).
3. Miller, G. W., and Thorne, D. W., Plant Physiol. (in the press).
4. Webster, G. C., Amer. J. Bot., 39, 739 (1952).
5. Lowry, D. H., Rosebrough, Nira J., Farr, A. L., and Randall, Rose J., J. Biol. Chem., 193, 265 (1951).