1. Bukasov, S. M., Suppl. 58 Pull. Appl. Bot. Leningrad, pp. 192 (1933), quoted by Salaman, Hawkes and others.
2. Salaman, R. N., J. Boy. Bori. Soc, 62, 61, 112, 153, 253 (1937).
3. Hawkes, J. G., "Potato Collecting Expeditions in Mexico and South America". Imp. Bur. of Plant Breeding and Genetics, 142 (1944).
4. Clusius, C., "Rariorum plantarum Historia" (Antwerp, 1601).
5. Quoted by Hackbarth, J. Zumul;chter, 7, 95 (1935).