Floral development and morphology of Vochysiaceae. I. The structure of the gynoecium.

Vochysiaceae are divided into two tribes on the basis of ovary structure (superior trilocular or inferior unilocular). The superior trilocular ovary has been considered basal in the family, and the term "pseudomonomerous" was used to indicate the presumed evolutionary derivation of the unilocular condition from the trilocular. However, recent evidence that Vochysiaceae are Myrtalean suggests that the superior ovary may be secondarily derived. In addition, published figures cast doubt on the interpretation of the putatively unilocular ovaries. To understand these features, floral ontogeny and anatomy were examined using scanning electron microscopy and serial sectioning. In all taxa examined, the ovary develops in an epigynous fashion, on a concave floral apex, supporting the hypothesis that the superior ovary is secondarily derived. Subsequent to initiation of the ovary, differential growth results in ovaries that are superior, inferior, or partly inferior in different genera. Sections of floral buds of the two unilocular genera, Erisma and Erismadelphus, show aborted locules in the latter but not in the former. The application of the term "pseudomonomerous" to both genera obscures this significant difference. The position of the placenta in the truly unilocular genus varies among species, suggesting a character transformation series from multilocular through intermediates to truly unilocular.