Chromosome Cytology, Pollen Structure, and Relationship of Retzia capensis

Abstract

A chromosome number of n - 12 is reported for Retzia capensis, and the pollen is described based on SEM and TEM studies. It is tentatively concluded that the recognition of the monotypic family Retziaceae is warranted. The family's closest affinity is with the Loganiaceae. Retzia capensis Thunb. is an unusual and striking member of the sclerophyll flora of the Cape region of South Africa. The genus is monotypic and its relationships are poorly known. It is a shrub with ericoid leaves and has a flower with a well-developed corolla tube, five epipetalous stamens, and a bicarpellate superior ovary. These characteristics place it among the less specialized of the tubiflorous group of families, but its correct relationships and family position remain unsettled. It is most frequently assigned to the Solanaceae or Loganiaceae, or is considered a separate family, but its relationships to these families remain unclear. A study of pollen structure and chromosome cytology has thus been made in the hope that this information may help in learning more about its phylogeny.