2. Perianth at the time of maturity firm, tubular, tightly clasping the fruit. Flowers unisexual. Annual herbs.--Species 2. North and South Africa, also naturalized in the Mascarene Islands. =Emex= Neck. Perianth at the time of maturity more or less membranous, not tubular and not clasping the fruit very tightly.--Species 45. Some are used as vegetables, for tanning and dyeing, or in medicine. “Dock.” =Rumex= L. 3. Seed with ruminate albumen. Shrubs with 5, 7-10, or 20-50 stamens. [Subfamily =COCCOLOBOIDEAE=.] 4 Seed with homogeneous albumen. Herbs or undershrubs, more rarely shrubs with 6 or 12-18 stamens. [Subfamily =POLYGONOIDEAE=.] 5 4. Flowers unisexual. Perianth-segments 4 or 6, the outer deciduous. Stamens 20-50. Erect shrubs or trees.--Species 1. West Africa. [Tribe TRIPLARIDEAE.] =Symmeria= Benth. Flowers hermaphrodite. Perianth-segments 5, united at the base into a tube becoming two-winged in fruit. Stamens 5-10. Mostly climbing, tendril-bearing plants.--Species 3. West Africa. [Tribe COCCOLOBEAE.] =Brunnichia= Banks 5. Stem woody, shrubby. Leaves small. Stamens 6 or 12-18. Filaments united at the base. [Tribe ATRAPHAXIDEAE.] 6 Stem herbaceous or woody at the base only. Stamens 8, more rarely 5-7. Filaments free, but sometimes inserted on a ring-shaped disc. [Tribe POLYGONEAE.] 7 6. Perianth-segments 4, the inner much enlarged in fruit. Stamens 6, the outer with a callosity at the base. Stigmas 2. Fruit glabrous. Embryo lateral. Leaves ovate or orbicular.--Species 1. Egypt. =Atraphaxis= L. Perianth-segments 5-6, not enlarged in fruit. Stamens 12-18, with a hairy appendage at the base. Stigmas 4. Fruit bristly. Embryo axile. Leaves linear or subulate.--Species 1. North Africa. =Calligonum= L. 7. Perianth-segments of the hermaphrodite and female flowers united below into a narrow tube. Flowers polygamous.--Species 17. Central and South Africa. Some are used as vegetables and for making bread. (Including _Raphanopsis_ Welw.) (Plate 39.) Oxygonum Burch. Perianth-segments not united below into a narrow tube. 8 8. Seed with broad, folded cotyledons. Perianth shorter than the fruit. Leaves cordate.--Species 1 (_F. esculentum_ Moench, buckwheat). Cultivated as a cereal or fodder-plant. (Under _Polygonum_ L.) =Fagopyrum= Gaertn. [Illustration: POLYGONACEAE. _FLOW. PL. AFR._ _Pl. 39._ J. Fleischmann del. Oxygonum sinuatum (Hochst. and Steud.) Benth. and Hook. _A_ Fruiting plant. _B_ Flower cut lengthwise. _C_ Fruit cut lengthwise.] [Illustration: CHENOPODIACEAE. _FLOW. PL. AFR._ _Pl. 40._ J. Fleischmann del. Traganum nudatum Del. _A_ Flowering branch. _B_ Part of a fruiting branch,. _C_ End of a branch. _D_ Flower with bracts and bracteoles. _E_ Flower cut lengthwise.] Seed with narrow, not folded cotyledons.--Species 50. Some are poisonous, others serve as ornamental, medicinal, or fodder-plants, or yield tanning and dyeing materials. =Polygonum= L. ORDER CENTROSPERMAE SUBORDER CHENOPODIINEAE