The parastic family Rafflesiaceae comprises 8 genera and about 50 species. The ovule and seed characters support the subdivision of the family by H. Harms (1935, Die natiirllichen Pflanzenfamilien, vol. 16 b). The ovules show two main evolutionary trends, viz. a change from anatropous towards orthotropous ovules (Rafflesieae and Cytineae) and one from bitegmic, as in Apodantheae, towards unitegmic ovules. The tribes Rafflesieae and Cytineae have rudimentary outer integuments, while the Mitrastemoneae are fully unitegmic. The nucellus is small and tenuinucellate throughout and degenerates early.