SEM images of stages of the floral development in Mussaendopsis beccariana. A–F: lateral views. A–B. Semi-mature flower with part of corolla removed. Calyx consisting of a calyx tube and calyx lobes. Corolla consisting of free petals embedded in the hypanthium (red arrow). Five stamens with tetrasporangiate dorsifixed and introrse anthers. Conspicuous annular nectary surrounding the style base (scar of removed style indicated by purple arrow). C. Longitudinally opened semi-mature flower with encircled in purple a placenta with multiple ovules filling up one out of two locules. Centrally in the flower, scar of removed style indicated by purple arrow. D–E. Mature stamen with stretched filament, longitudinally opened tetrasporangiate dorsifixed and curved anther. E. Detail of anther. F. Detail of style and two stigmas. Colour code: green, calyx; purple, gynoecium; red, corolla; yellow, androecium. Symbols: a, anther; ca, calyx (lobe); f, filament; ne, nectary; pc, pedicel; pe, petal; sg, stigma; st, style.

  Part of: Vrijdaghs A, De Block P, De Toni KLG, Smets E, Robbrecht E (2022) Floral ontogeny links Dialypetalanthus (Condamineeae) with the floral developmental morphology of other Rubiaceae. Plant Ecology and Evolution 155(3): 394-403.