The breeding systems of Stylidiurn grarninifolium and S. producturn (= S. grarninifoliurn var.
caulescens) were studied by observing the phenology of individual flowers and inflorescences, and relating
the data to a series of pollination experiments within and between the species. Inter-specific pollinations
yielded similar levels of seed-set to crosses within the species indicating a close relationship
between the taxa. Self-pollination of either species is uncommon; however, when it occurs, the majority
of selfed ovules are aborted post-zygotically, probably by a system of recessive lethals, as there is no
indication of an incompatibility system. It is concluded that the breeding systems of S. grarninifoliurn
and S. productum, two of the few eastern Australian species, are similar to those of many Stylidiurn
species from the south-west, casting doubt upon hypotheses that the breeding system has led to high
rates of speciation in the south-west.