1. ASEN, S., andLarson, R. E. (1951). Artificial culturing of rose embryos.Pennsylvania State College Progress Rep. No. 40.
2. Barakat, S. E. Y. (1958). Organic acid metabolism in plants with particular reference to rose hips.Ph.D. Thesis, Univ. of Wales.
3. Crocker, W. (1948). Growth of plants. Reinhold, New York.
4. Crocker, W., andBarton, L. V. (1953). Physiology of seeds, pp. 117–20. Chronica Botanica Co., Waltham, U.S.A.
5. Mainland, D.Herrera, L., andSutcliffe, M. I. (1956). Tables for use with binomial samples. Dept, of Med. Statistics, New York Univ. Coll. of Medicine.