The morphology of false anthers in Craterostigma plantagineum and Torenia polygonoides (Scrophulariaceae)

The ontogenesis of the prominent excrescences of the filament of two melittophilous species is investigated and the biological implications are discussed. In Craterostigma plantagineum Hochst. the bases of the filament bulges are fused with the lower lip of the corolla. The bulges are bright yellow, of grainy structure, and they flank the entrance of the flower tube. This character syndrome can be interpreted as a plastic (three-dimensional) false anther or anther dummy. The flower of Torenia polygonoides Benth. carries a yellow, spotlike anther dummy in the centre of the lower lip. The staminal excrescences of T. polygonoides are completely free of the lower lip of the corolla, pin-shaped, and of a light pink colour. Thus, they lack the characteristic, yellow signal colour that is typical for anther dummies in general. Possibly, they have no optical function at all, but act as a guide rail.