Floral Morphological Studies in the South African Cyphia stenopetala Diels (Cyphiaceae)

Abstract

Cyphia stenopetala is a member of the monogeneric South and tropical African family Cyphiaceae, which is characterized by a pollen‐presenting box formed by the five (empty) anthers as walls and the stylar tip as the bottom. Cyphia stenopetala uses the pollen box for self‐fertilization. Pollen is shed into the pollen box, where it germinates, and the pollen tubes form a dense felt. We assume that the pollen box in C. stenopetala is an area for an increased pollen tube competition presumably compensating for possible inbreeding depression. Flowers of outbreeding Cyphia species are distinctly proterandrous, but in the selfing C. stenopetala, flowers are proterogynous. A mucilaginous liquid secreted from the enlarged stylar channel at the top of the style may cause pollen germination. Self‐fertilization in C. stenopetala appears to be a recent evolutionary event because all flowers investigated produce nectar, and different populations can differ in time and degree of pollen germination.