Heterostyly in Lithospermum cobrense (Boraginaceae)

Lithospermum cobrense Greene exhibits the floral dimorphisms and strong self-incompatibility system typical of most distylous plants. Flowers of the long styled (pin) form produce smaller pollen grains but more pollen per flower than flowers of the short styled (thrum) form. Corollas of pins and thrums are equal in size. The breeding system of L. cobrense is less specialized than, and probably ancestral to, that of L. caroliniense.