Description from Flora of China
Herbs, shrubs, or trees, usually with dense rosettes of very fleshy leaves. Stems often very reduced but sometimes well developed or even with secondary thickening. Leaves rosulate, amplexicaul, thick, succulent, always glabrous, margin mostly hard dentate or spiny, apex sharply pointed. Inflorescence a subterminal, ascending to erect raceme, often branched; peduncle usually well developed; bracts persistent, scarious. Pedicel usually much shorter than perianth. Perianth usually red, orange, or yellow, rarely greenish or whitish, cylindric to 3-sided, sometimes slightly curved or with swollen base; segments usually connate to form a tube, very rarely nearly free, usually glabrous, apex spreading. Stamens 6, inserted at base of perianth tube, usually exserted; filaments subulate; anthers dorsifixed. Ovary 3-loculed; ovules many per locule. Style filiform; stigma small. Fruit a loculicidal capsule. Seeds 3-angled or flattened, often winged.
Between 350 and 400 species: S and tropical Africa (including Madagascar), tropical Arabia; one species (introduced) in China.