• Darlington, C. D. (1971) The evolution of polymorphic systems. In: Ecological Genetics and Evolution (Ed. by E. R.Creed), pp. 119. Blackwell, Oxford .
  • Darwin, C. (1877) The Different Forms of Flowers on Plants of the Same Species. Murray, London .
  • Dowrick, V. P. J. (1956) Heterostyly and homostyly in Primula obconica. Heredity 10, 219236.
  • Dulberger, R. (1975) S gene action and the significance of characters in the heterostylous syndrome. Heredity 35, 407415.
  • Golynskaya, E. L., Bashkirova, N. V. & Tomchuk, N. N. (1976) Phytohaemagglutanins of the pistil in Primula as possible proteins of generative incompatibility. Soviet Plant Physiology 23, 6977.
  • Heslop-Harrison, Y., Heslop-Harrison, J. & Shivanna, K. R. (1981) Heterostyly in Primula. 1. Fine-structural and cytochemical features of the stigma and style in Primula vulgaris Huds. Protoplasma 107, 171187.
  • Lewis, D. (1942) The physiology of incompatibility in flowering plants. 1. The effect of temperature. Proceedings of the Royal Society of London B131, 1326.
  • Mather, K. (1950) The genetical architecture of heterostyly in Primula sinensis. Evolution 4, 340352.
  • Mather, K. & de Winton, D. (1941) Adaptation and counter-adaptation of the breeding system in Primula. Annals of Botany (n.s.) 5, 297311.
  • Mattsson, O. (1983) The significance of exine oils in the initial interaction between pollen and stigma in Annals maritima. In: Pollen Biology and Applications for Plant Breeding (Ed. by D. L.Mulcahy & E.Ottaviano), pp. 257267. Elsevier, Holland .
  • Richards, A. J. (1986) Plant Breeding Systems. Allen and Unwin, London .
  • Richards, A. J. & Ibrahim, H. (1982) The breeding system in Primula veris L. n. Pollen tube growth and seed set. New Phytologist 90, 305314.
  • Richards, A. J. & Mitchell, J. (1990) The control of incompatibility in distylous Pulmonaria affinis Jordan (Boraginaceae). Botanical Journal of the Linnean Society (in the press).
  • Schou, O. (1984) The dry and wet stigmas of Primula obconica: ultrastructural and cytochemical dimorphisms. Protoplasma 121, 99113.
  • Schou, O. & Mattsson, O. (1985) Differential localization of enzymes in the stigmatic exudates of Primula obconica. Protoplasma 125, 6574.
  • Schwarz, O. (1968) Beitrage zur kenntnis der gattung Primula. Wissenschaftliche Zeitschrift der Friedrich-Schiller Universität Jena Mathematisch-Naturwissenschaftliche Reihe 17, 307332.
  • Shivanna, K. R., Heslop-Harrison, J. & Heslop -Harrison, Y. (1981) Heterostyly in Primula. 2. Sites of pollen inhibition, and effects of pistil constituents on compatible and incompatible pollen-tube growth. Protoplasma 107, 319337.
  • Shivanna, K. R., Heslop-Harrison, J. & Heslop-Harrison, Y. (1983) Heterostyly in Primula. 3. Pollen water economy: a factor in the intramorph incompatibility response. Protoplasma 117, 175184.
  • Spanowsky, W. (1962) Die bedeutung der pollenmorphologie fur die taxonomie der Primulaceae-Primuloideae. Feddes Repertorium 65, 149207.
  • Stevens, V. A. M. & Murray, B. G. (1981) Studies on heteromorphic self-incompatibility systems: the cytochemistry and ultrastructure of the tapetum of Primula obconica. Journal of Cell Science 50, 419431.
  • Stevens, V. A. M. & Murray, B. G. (1982) Studies on heteromorphic self-incompatibility systems: physiological aspects of the incompatibility system of Primula obconica. Theoretical and Applied Genetics 61, 245256.
  • Wedderburn, F. (1988) A comparison of heteromorphic incompatibilities in Primula. Ph.D. Thesis, University of Newcastle-upon-Tyne.
  • Wendelbo, P. (1961) An account of Primula subgenus Sphondylia with a review of the subdivisions of the genus. Arbok Universitet Bergen, Matematisk-Naturvitenskapelig 11, 3343.