Distyly and pollen dimorphism inLinum suffruticosum (Linaceae)

The Mediterranean distylousLinum suffruticosum has dimorphic pollen. That from short-styled plants has sub-monomorphic surface excrescences with minute papillae; that from long-styled plants has strongly dimorphic excrescences with conspicuous papillae. The differences are much like those described in species of other sections of the genus. Pollen of the related homostylousL. tenuifolium has monomorphic pollen. It combines characteristics of bothL. suffruticosum types but resembles that of the long-styled plants somewhat more closely. Ribbonlike styles of long-styled plants ofL. suffruticosum provide another feature which seems to be controlled by the S supergene thought to be associated with distylic incompatibility. The pollen ofL. suffruticosum andL. tenuifolium is very similar to that of some species of sectionLinastrum and would support their placement in that section.