Floral ontogeny and morphology in subfamily Amygdaloideae T-& G-(Rosaceae)

Relationships within the Amygdaloideae have long been a point of discussion in Rosaceae systematics. Oemleria, a monotypic genus, has been removed fro m the Amygdaloideae because of its five-pistillate gynoecium since all othe r genera have a single pistil. Exochorda, with its capsular fruit, has trad itionally been placed in Spiraeoideae. Nevertheless, recent phylogenetic an alyses of wood anatomy and rbcL sequence variation have demonstrated that b oth Exochorda and Oemleria should be included in an expanded Amygdaloideae. Comparisons of floral ontogeny in Prunus, Oemleria, and Exochorda, and the mature morphology of these genera and Prinsepia, support inclusion of Oeml eria and Exochorda in Amygdaloideae. Inflorescence development demonstrates a close relationship between Exochorda and Oemleria. Gynoecium development in Erochorda and Oemleria is similar in some ways to that of some members of the Maloideae. All genera have a pair of collateral, bitegmic ovules, ea ch of which is associated with an obturator that is composed of cells of th e ventral margin of the locule.