Studies on the embryology and gynoecium structures inDrimys winteri (Winteraceae) and someAnnonaceae

Drimys winteri (Winteraceae) and 11 species ofAnnonaceae, namelyAnnona montana, Artabotrys hexapetalus, Bocagea sp.,Papualthia sp.,Polyalthia nitidissima, Tetrameranthus umbellatus, T. duckei, Uvaria sp.,Xylopia malayana, X. aromatica, andX. emarginata, were investigated embryologically with special reference to development of ovule and embryo sac. The ovules are anatropous, crassinucellate and in most taxa bitegmic. The inner integument is of epidermal origin. TheAnnonaceae investigated have a multi-layered, later vascularized outer integument with most probably subepidermal initiation. In contrast,Drimys winteri has a three-layered, non-vascularized outer integument of epidermal origin. The annonaceous genusTetrameranthus (T. umbellatus andT. duckei) possesses a middle integument between the inner and the outer one, stated here for the first time in a neotropic representative ofAnnonaceae. Within the angiosperms this feature occurs inAnnonaceae only. The embryological characters are rather homogeneous. Differences between the species investigated are found in, e.g. the number of cell layers in the inner integument, which is commonly two inAnnonaceae as compared to three inDrimys winteri, the presence or absence of a hypostase, the number of layers in the nucellar epidermis, great differences in size of ovules, and the species-specific pattern of tannin deposition in the ovules. In the species so far investigated the embryo sacs develop according to thePolygonum-type. InXylopia malayana andBocagea sp. in addition the carpels were investigated. They are conduplicate. InXylopia malayana the free carpels are united by an extragynoecial compitum, inBocagea sp. each stigma produces its isolated mucilage cap. The results obtained from the investigated taxa are discussed and compared with published data on embryology and gynoecium structure in other annonaceous and winteraceous taxa.