• Supported in part by grants from the American Orchid Society Fund for Research and Education, the Orchid Digest Corporation, the Stanley Smith Horticulture Trust, the Textilana Corporation, Office of Naval Research (US) Contract NR 108–796 (all to J. Arditti) and a Scholarship (to Mary-Ellen Churchill) from the Orange District Women's Clubs. We thank Brigitta H. Flick for technical assistance: Dr D. G. Lawrence and Robert Ernst for many fruitful conversations and Nanette M. Hogan for reading and commenting on the manuscript. Plants were donated by Mr and Mrs E. W. Charles; Hugo Freed, Arthur Freed Orchid Co.; Robert Jones, Rod McLellan Orchid Co.; Robert I. Norton and Mrs S. Mosher, Dos Pueblos Orchid Co.; Frank Cobb, Clyde Smith and Rex Smith, Universal Orchid Co. We are especially grateful to Dr G. Hadley for reading and correcting the proofs.


Leaf-tips of Epidendrum and Laeliocattleya (Orchidaceae) have been cultured in vitro. Epidendrum seedling leaf-tips form calli on Murashige-Skoog medium (MS) or after being transferred to Knudson C agar following prior growth on MS. Plantlets also develop from tips of young leaves of mature Laeliocattleya plants cultured in Heller's medium or in a solution specifically devised for orchid shoot-tip cultures. In Heller's medium plantlet development is preceded by callus formation whereas in the shoot-tip medium protocorm-like bodies are formed first. These tissues when subcultured from Heller's medium or the shoot-tip solution to Knudson C agar also produce plantlets which resemble orchid seedlings. The results are discussed in relation to the components of each medium, the requirements of germinating orchid seeds and protocorms, and the difficulties encountered in attempts to culture tissues of mono-cotyledonous plants.