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Succulent annual or perennial herbs. Leaves alternate, flat, entire, with a closed basal sheath. Flowers usually bisexual, regular, hypogynous in terminal panicle or axillary cymes.Perianths of two series, each with three segments, the outer generally free, green imbricate sepals, the inner equal petals inn some petals fused into a tube. Stamens 6, all fertile or 2 or more reduced to staminodes, filaments often bearded, anthers often dissimilar. Ovary superior, of 3 or 2 fused carpels with locules (rarely two), one to several orthotropus ovules, placentation axile. Fruit a thin-walled dehiscent capsule, but rarely may be fleshy and indehiscent. Seeds usually angled, surface with smooth or rugose.

Key to the Genus

Serial Key Reference
1a. Fruit indehiscent, crustaceous or baccate; flowers always in terminal panicles Pollia
1b. Fruit a loculicidal capsule; flowers in terminal or axillary cymes or panicles 2
2a. Inflorescence terminal 3
2b. Inflorescence axillary 8
3a. Inflorescence subtended by 1 or 2 spathaceous bracts or closely invested by upper leaves 4
3b. Inflorescence not subtended by spathaceous bracts nor closely invested with upper leaves 7
4a. Perfect stamens 3; petal free Commelina
4b. Perfect stamens 6 5
5a. Spathaceous bracts single Cyanotis
5b. Spathaceous bracts two 6
6a. Petals more than 1 cm long, connate at base only Trdeacantia
6b. Petals less than 1 cm long, united into a tube Zebrina
7a. Panicle second; fertile stamens 6 or 5, staminodes 0 Floscopa
7b. Panicles not second; fertile stamens 3 rarely 2, often accompanied by staminodes Murdannia
8a. Inflorescence perforating and emerging from the base of subtending leaf sheath Amischotolype
8b. Inflorescence exerted from top of subtending leaf sheath 9
9a. Flowers borne in an involucre of boat-like overlapping bracts; leaves thick, stiff Rhoeo
9b. Flowers embedded in bulged leaf sheath Amischophacelus