1. Gautheret, R. J., Corn pt. rend. acad. sci. 208: 118 (1939).
2. Nobecourt, P., Compt. rend. Soc. biol. 130: 1270 (1939).
3. Riker, A. J., Growth and Differentiation in Plants: 393 (1953).
4. POTENTIALLY UNLIMITED GROWTH OF EXCISED PLANT CALLUS IN AN ARTIFICIAL NUTRIENT
5. Haberlandt, G., Sitzber. Akad. Wiss. Wien, Math.-naturw. Kl. 3: 69 (1902).