Ovule morphology, megasporogenesis and megagametogenesis of ten species of Oxalis were examined. The ovule is anatropous, bitegmic and the integuments form a zig-zag micropyle. The type of female gametophyte development is variable in the studied species. The majority of them have a monosporic Polygonum-type female gametophyte. Two of the studied species show binucleate dyad members, so they have a bisporic Allium-type female gametophyte. Only O. articulata follows tetrasporic Adoxa-type development of the megagametophyte. This is the first report of a tetrasporic female gametophyte in Oxalidaceae. The endosperm is nuclear, and development of the embryo corresponds to the Solanad type.