Penaea is a small genus of evergreen flowering shrubs in the family Penaeaceae, within the order Myrtales. The genus is endemic to southern South Africa, where members grow as leathery-leaved shrubs typical of the Cape flora. The family Penaeaceae, which contains nine genera and approximately 29 species, is itself confined to South Africa.
The genus is of particular botanical interest for its highly distinctive embryo sac development. After two successive rounds of mitosis, four nuclei are formed at each pole, producing a mature embryo sac that contains four polar groups each composed of three cells — an architecture not found in the vast majority of flowering plants. This configuration, when it occurs elsewhere in the plant kingdom, is formally termed "Penaea-type" in recognition of the genus. GBIF records approximately 18 accepted species and infraspecific taxa within Penaea, including Penaea cneorum and Penaea mucronata. The plants are commonly known as "Brickleaves."
Distribution
Penaea is endemic to southern South Africa, where the genus occurs as part of the diverse Cape flora. As members of the family Penaeaceae — a family restricted entirely to South Africa — all species are confined to that country's southwestern and southern regions.
Taxonomy Notes
Penaea belongs to the family Penaeaceae within the order Myrtales. Under the APG III classification system, the family Penaeaceae was expanded to include the formerly separate genera Olinia (previously in Oliniaceae) and Rhynchocalyx (previously in Rhynchocalycaceae). GBIF recognises approximately 18 accepted taxa in the genus, with no synonyms recorded in the current backbone.
