1. Hansch, C., and Muir, R. M., Plant Growth Regulation (Iowa State College Press, Ames) (in the press).
2. Heilbronner, E., Non-benzenoid Aromatic Compounds, 171 (Interscience Pub., Inc., New York, 1959).
3. Muir, R. M., and Hansch, C., Plant Physiol., 28, 218 (1953).
4. Wain, R. L., and Wightman, F., Proc. Roy. Soc., B, 142, 525 (1954).
5. Veldstra, H., and van de Westeringh, C., Rec. trav. chim., 70, 1113 (1951).