The discriminating characters of some genera of the family Stemonaceae (incl. Stemona) and the genus Pentastemona (formerly in the Stemonaceae) have been amply discussed by the present author (1991). The discussion resulted in the statement that Pentastemona represents a family of its own, Pentastemonaceae, beside Stemonaceae. The forthcoming treatment of both families in Flora Malesiana (Duyfjes, 1992) requires the formal description of Pentastemonaceae. The supporting considerations for the distinction of the new family are briefly enumerated again: Pentastemonaceae (Pentastemona) Stemonaceae Growth habit monopodial sympodial Leaves dispersed distichous, opposite or verticillate Petioles shortly sheathing at the base not sheathing at the base Scale leaves on the rootstocks no scale leaves present Inflorescences essentially compound not compound Flowers 5-merous, tepals and stamens in one whorl each 4-merous, tepals and stamens each in two whorls of two Stamens connectives, together with the top of the hypanthium and the ovary grown into a complicated disk-like structure filamentous, connectives narrow or broad, mostly with conspicuous appendages; see Van Heel (1992) Ovary inferior with three parietal placentas; ovules many, anatropous superior (Stemona) or semi-inferior (Stichoneuron), with placentas basal (Stemona) or apical ( Stichoneuron), with few or many anatropous or semi-anatropous ovules Pedicels not articulated articulated Fruit inferior, berry-like superior (Stemona) or semi-inferior (Stichoneuron); Seed seeds with sarcotesta-like hyaline exotestas; arillode inflated a 2-valved capsule seeds without sarcotesta-like exotestas; arillode various, not inflated; see Bouman & Devente (1992) Pollen Exine inaperturate, scabrate sexine architecture distinct from Pentastemona; see Van der Ham (1991)