Wiry perennial herbs or occasionally suffrutices up to 1.1 m tall, glabrous to pubescent, with stems erect (sometimes caespitose) to spreading or creeping and rooting and branching from taproot, often woody at base, with or without condensed sterile basal or axillary shoots; dark (black) glands, when present, confined to petal and/or sepal margin and sometimes 1–5 also at leaf apex, rarely elsewhere in leaf. Stems (4)2-lined to terete, sometimes with orange or black glands. Leaves opposite, decussate, sessile or petiolate, free, persistent or deciduous, herbaceous to coriaceous; lamina entire with venation pinnate, with or rarely without up to 3 pairs of lateral veins; laminar glands all pale (rarely a few with dense contents appearing dark); intramarginal glands (sometimes apparently marginal) all pale or sometimes 1–5 apical black; ventral glands absent. Inflorescence 1- to∞-flowered, with branching dichasial or monochasial, from 1–7 nodes, with floweringbranches from up to 4 nodes below (or more in 15. thymifolium); buds usually erect (recurved in 22. monadenum and 27. taygeteum). Flowers stellate, homostylous. Sepals 5, unequal to equal, free or up to 0.6 united, imbricate, persistent, erect in fruit, with margin entire and eglandular or regularly or partially glandular-ciliate to -fimbriate; veins (1)3–5, outer sometimes branching; laminar glands pale, linear to punctiform; marginal glands black, obconic to globose or ellipsoid or absent. Petals 5, persistent, not unguiculate (cf. Sect. 17), erect or rarely spreading after flowering, without apiculus, usually red-tinged or orange- or red-veined; margin with sessile glands or glandular-ciliate or rarely entire; laminar glands pale, striiform to punctiform or absent; marginal glands black, globose to ellipsoid. Stamen fascicles ‘3’ (i.e. 2+2+1), persistent, with stamens totalling 25–60, basally united in each fascicle; anther yellow or rarely orange (3. hirsutum pro min. parte) or red (2. pulchrum), gland amber; pollen type X. Ovary with 3 axile placentae, each ∞-ovulate; styles 3, divergent from discrete bases; stigmas small. Capsule 3-valved, coriaceous to papyraceous, longitudinally vittate. Seeds cylindric or ± elongate, not carinate or appendiculate; testa papillose to shallowly rugulose.