Penaeaceae is a small myrtalean family of seven genera and 23 species endemic to the Western Cape Province of South Africa. All species are confined to the Cape "fynbos" vegetation, but occur in different habitats such as dry, vertical rock cliffs and moist, sandy streambeds. Growth forms range from small, decumbent, much-branched shrublets to few-branched shrubs up to four meters tall. Flowers are tetramerous, actinomorphic, hypogynous, and have a single whorl of perianth organs inserted on the rim of a hypanthium. Stamens alternate with the perianth lobes and are in some species inflexed in bud. The gynoecium is 4-locular; each locule contains 2 or 4 anatropous, bitegmic, crassinucellar ovules. The stigma is either capitate with a uniform stigmatic area or 4-winged with four stigmatic areas separated by commissural lobes. Recent molecular studies in the Myrtales strongly support Penaeaceae to be part of a clade also comprising the two African families Oliniaceae and Rhynchocalycaceae plus the South American family Alzateaceae. This Western Gondwanan clade is sister to the South East Asian Crypteroniaceae. We have compiled a molecular data set comprising sequences of six chloroplast regions (three intergenic spacers, two exons, one intron) for 19 of the 23 species of Penaeaceae plus representatives of the closely related families. Our results clearly support the monophyly of Penaeaceae. However, within the family our molecular results conflict with traditional classifications. In this study, we discuss floral development and structure of Penaeaceae in the light of our molecular phylogeny, with emphasis on the anther and gynoecium.

Key words: floral development, floral structure, molecular phylogeny, Myrtales, Penaeaceae