The genus Eugenia (Myrtaceae) in southern Africa: Ontogeny and taxonomic value of the seed

Eugenia L. in southern Africa constitutes two coordinate groups of species (groups X and Y). Each group is characterized by a particular type of seed (types X and Y respectively). This study concerns the ontogeny of both seed types. Results are compared with the literature to evaluate its taxonomic significance.In both groups the ovules are hemi-campylotropous, occasionally tending to be ana-campylotropous, sessile or sub-sessile, bitegmic and crassinucellate. Usually only one ovule per ovary matures into an overgrown seed. Abortive ovules are transformed into ovulodes.Ovules in seed type X become amphitropous resulting in sub-reniform or oblong-globose seed. A short funicle is discernible; the hilum is not extended. The testa develops from the outer integument and is relatively thin (0,1 – 0,5 mm), not multiplicative and tends to be exotestal. Two areolae pervaded by vascular strands are present. Secretory cavities develop in the cotyledons. Starch, occasionally with unidentified spherical bodies, is the main storage product. Abundant endosperm is formed.Seed type Y is globose, pachychalazal and sessile with an extended hilum. The testa is relatively thick (0,5 – 1,0 mm), multiplicative, mesotestal and pervaded by vascular strands. Secretory cavities are absent from the cotyledons. Starch is the only storage product. Relatively little endosperm is formed.Generic rank is proposed for both groups. Group X is treated as congeneric with Eugenia s. str. whereas group Y probably represents a new generic segregate