1. Osborne, D. J., in Transport of Plant Hormones (edit. by Vardar, Y.), 97 (North Holland, Amsterdam, 1968).
2. Sachs, T., Ann. Bot., 33, 263 (1969).
3. van Overbeek, J., Bot. Gaz., 100, 133 (1938).
4. van Overbeek, J., Amer. J. Bot., 33, 263 (1947).
5. Hertel, R., and Leopold, A. C., Planta (Berl.), 59, 535 (1963).