Gametogenesis in Galbulimima belgraveana (Himantandraceae)

Abstract

The flowers of Galbulimima belgraveana (F. Muell.) Sprague are bisexual, calyptrate and protogynous. The numerous free stamens are laminar and arranged spirally on an elongated receptacle; only the middle stamens are fertile. There are four microsporangia embedded on the abaxial side of the microsporophyll. The tapetum is secretory and often double. A variety of spore tetrad types is produced. The mature pollen grains are single, monosulcate, scabrate, atectate, spheroidal and 2-celled.

The carpels of a flower are initially free but later become concrescent so that a single fruit is formed. The ovules are anatropous, crassinucellar and bitegminal, and show an elongated embryo sac that conforms to the polygonum type of development. There is a massive parietal tissue in early stages of ovule development. In its embryological features, the species shows close relationships to the families Annonaceae and Degeneriaceae and, to a slightly lesser extent, the Magnoliaceae and Eupomatiaceae.