Perennial herbs up to 1m tall, with stems erect to prostrate, creeping and sometimes branching at base, glabrous, with dark (black or rarely red) glands on leaves, sepals (rarely absent), petals and anthers; branching lateral, from various nodes. Stems (mature) terete or rarely (when slender) 2-lined, eglandular. Leaves opposite, decussate, sessile or up to 10 mm pseudopetiolate, free, persistent; lamina entire or sometimes wholly or proximally gland-fringed, sometimes with gland-fringed auricles, with venation pinnate, closed and tertiary reticulation dense to lax; laminar glands punctiform, pale and/or black, relatively large (cf. Sect. 9e), dense; marginal glands dark, dense to sparse; ventral resin glands absent. Inflorescence 1- c. 50-flowered, with branching dichasial and/or monochasial, from 1-4(-6) nodes, often with subsidiary branches below; bracts and bracteoles entire to gland-fringed and often glandular-auriculate, reduced. Flowers stellate or rarely infundibuliform, homostylous. Sepals 5, free, persistent, erect or rarely spreading in fruit, with margin entire to glandular-ciliate; veins 3-5; laminar glands pale and/or dark, linear to punctiform; marginal and/or intramarginal glands dark. Petals 5, persistent, erect after flowering, with or without apiculus, margin entire, with or rarely without immersed or sessile dark glands, or glandular-ciliate; laminar glands pale and/or dark, linear to punctiform, or rarely absent. Stamen fascicles 5, united 2+2+1 (i.e. '3'), persistent, with stamens totalling 9-c. 60; filaments basally united; anther gland dark; pollen type X. Ovary with 3(4) completely axile placentae, each ¥-few-ovulate; styles 3(4), free, divergent from discrete bases; stigmas narrowly capitate to claviform. Capsule 3(4)-valved, chartaceous to papyraceous, with valves longitudinally vittate. Seeds cylindric, not (rarely scarcely) carinate or appendiculate; testa scalariform-reticulate to scalariform or foveolate.