Erythraea Borkhausen.

Annuals. Stems erect, obscurely 4angled. Leaves opposite. Cymes pseudodichotomous, sometimes spicate. Flowers [4 or] 5merous. Calyx lobed nearly to base. Corolla salverform, lobes shorter than tube. Stamens inserted at throat of corolla tube; filaments filiform, erect at first, helically coiled later; anthers dehiscing longitudinally. Ovary partly 2-locular. Style linear; stigma lobes orbicular. Capsules 2valved, many seeded. Seed coat alveolate.

40-50 species: worldwide except subsaharan Africa; two species in China.