Erect or prostrate annual or perennial herbs with 4-angled stems. Stipules connate with the petioles to form a sheath. Leaves opposite; lamina linear-lanceolate to ovate or broadly elliptic. Inflorescence dense spherical sessile terminal or axillary heads. Calyx tube obconic, obovoid or subglobose; teeth 4–5, 2 often longer; corolla salver-shaped or funnel-shaped, lobes 4. Fruit a thin circumscissile capsule, the upper part splitting off together with the calyx lobes, the septum persistent. Seeds oblong or globose, endosperm fleshy.
Worldwide: 30-40 species mostly in South America.
Zambia: 1 taxon. |
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