Floral anatomy of the Milla complex genera (Themidaceae)

Abstract

Floral morpho-anatomy of the Milla complex genera (Themidaceae) was studied with the aim to confirm the occurrence of a gynophore in Dandya, to determine if there are anatomical characters that allow to distinguish Dandya from the rest of genera of the complex (Behria, Bessera, Jaimehintonia, Milla, and Petronymphe), and to understand their evolution. Floral buds of ten species of the Milla complex were studied through the standard paraffin microtechnique. The results demonstrated the presence of a gynophore without pith in Dandya, while the other genera have a gynophore with pith. In addition, Dandya differs from the other genera of the complex by a closed-stigma with external papillae, nectary cavities of horned-shape with tabular epidermal cells, and filaments with 4-strata of parenchyma cells. Behria and Bessera share characters such as connated stamens and an ovary with the external epidermis papillose. Attributes like gynophore with pith, percentage of adnnation between ovary and floral tube of 20-30%, stigma with an open ending, and nectary cavities with discoidal shape are probably ancestral conditions in the Milla complex, from which transformation of character states occurred mostly in Dandya.