Homing in on heterostyly

The majority of plants are hermaphrodite and produce both male and female gametes. In addition to the various contrivances by which plants facilitate outcrossing--using wind, insects and other animals--an elaborate range of mechanisms has evolved to prevent self-fertilization. One such mechanism, known as oral heteromorphy, results in the development of different forms of self-incompatible owers on different individual plants (Darwin, 1877). Development of the distinct oral morphs with different anther height and style lengths is orchestrated by the S locus (see Richards, 1997).