7. Flowers unisexual or polygamous; no sterile ones. Filaments free.--Species 20. Some of them have edible seeds or are used as vegetables, in medicine or as ornamental plants. (Including _Albersia_ Kunth, _Amblogyna_ Rafin., and _Euxolus_ Rafin.) =Amarantus= L. Flowers hermaphrodite. Partial inflorescences consisting of one fertile and two sterile flowers. 8 8. Sterile flowers comb-shaped. Filaments free. Style short; stigma 2-lobed.--Species 1. Tropical and North Africa. Used as a vegetable. =Digera= Forsk. Sterile flowers wing-shaped. Filaments united at the base. Style long; stigmas 2.--Species 1. Northern East Africa (Somaliland). =Pleuropterantha= Franch. 9. Flowers solitary in the axil of each bract. 10 Flowers in clusters of two or more; usually some of them sterile. 20 10. Spurious staminodes (sterile processes) interposed between the fertile stamens. 11 Spurious staminodes wanting. 18 11. Perianth densely covered with silky or woolly hairs. 12 Perianth glabrous or scantily hairy. 15 12. Perianth-segments firmly leathery, silky-hairy, 3-nerved. Shrubs. Leaves alternate, fleshy.--Species 1. South Africa to Damaraland. (Under _Sericocoma_ Fenzl). =Calicorema= Hook. fil. Perianth-segments more or less membranous. 13 13. Branches jointed. Leaves very small, opposite, ovate, acuminate. Undershrubs.--Species 1. Southern West Africa (Hereroland). =Arthraerua= Schinz Branches continuous. 14 14. Perianth-segments silky, more or less thickened and hardened at the base, 1-nerved. Flowers small. Ovary hairy. Stigma capitate.--Species 8. Southern and Central Africa. =Sericocoma= Fenzl Perianth-segments woolly, not thickened. Flowers very small, in dense spikes.--Species 10. Some are used as vegetables or as ornamental plants. (_Ouret_ Adans.) =Aerva= Forsk. 15. Spurious staminodes minute, narrow, acute, unappendaged. Perianth-segments brownish-red, stiff-leathery, large, oblong, 3-nerved. Inflorescence head-like, ovoid. Leaves usually alternate. Undershrubs.--Species 1. Southern West Africa (Angola and Congo). =Mechowia= Schinz Spurious staminodes more or less quadrate, fringed or appendaged. Leaves opposite. 16 16. Spurious staminodes fringed below the top. Perianth-segments erect, oblong, blunt, thickened below. Flowers erect, spicate. Leaves small, sessile, linear-oblong. Herbs.--Species 1. Southern East Africa. (Under _Pandiaka_ Hook. fil.) =Argyrostachys= Lopr. Spurious staminodes fringed at the top or prolonged into appendages. Perianth-segments pointed. Flowers usually bent downwards. 17 17. Perianth-segments red or yellow, elliptical, hardened at the base, faintly 1-5-nerved. Shrubs or undershrubs.--Species 7. Central Africa to Transvaal. =Centema= Hook. fil. Perianth-segments white, green or brown, lanceolate, stiff-leathery, usually 3-ribbed.--Species 30. Some of them yield a substitute for soap or are used in medicine. (Including _Achyropsis_ Moq. and _Pandiaka_ Moq.) (Plate 41.) =Achyranthes= L.