Floral development and morphology of Vochysiaceae. II. The position of the single fertile stamen

Abstract

A conspicuous feature of Vochysiaceae flowers is their single fertile stamen. In some genera, the stamen is in front of a petal, whereas in others it is in front of a sepal. This difference has been attributed to two independent reductions, which implies the stamen is not homologous across the family. The observation that genera with an antesepalous stamen have only one petal, whereas those with an antepetalous stamen have three or five petals, led us to the hypothesis that in all genera the stamen arises in an antepetalous position, but that it is displaced during development in single-petaled taxa. We examined developing buds of five genera using scanning electron microscopy and serial sectioning and conclude that the stamen in all genera is fundamentally antepetalous. The stamen is not displaced. The petal, however, appears to be displaced in some genera. Further, the position of the fertile stamen in Erisma has been misinterpreted. We discuss the evolution of the androecium in this family in a phylogenetic context and consider the significance of symmetry and of loss vs. suppression in the development of Vochysiaceae flowers.