Annual or perennial herb up to 70 cm. tall, glabrous, sometimes rough, never glandular-pubescent, sometimes a subshrub with several ± erect or trailing herbaceous shoots and woody base; stems not much branched. Leaves 5–50 × 0·5–4 mm., alternate, subopposite or fasciculate, narrowly linear to lanceolate, entire, with prominent midrib below; petiole short, with swollen base. Inflorescences terminal and lateral, 5–50-flowered, pedunculate, umbelliform, laxly branched. Flowers small, greenish-white; pedicels up to 2 mm. long; bracteoles membranous, whitish, lanceolate. Perianth-segments 5, 2–3 mm. long, slightly unequal, membranous, whitish but with greenish keel, broadly ovate, obtuse, mucronate. Staminodes 0(-5), when present very small and caducous. Stamens 7 with filaments enlarged and fimbriate below. Ovary 2-lobed, glabrous. Mericarps sometimes bigger than perianth-segments, with 2 usually large smooth auricles at base, the outer face alveolate-tuberculate to spinescent.
