Fls solitary or in few-fld cymes. Sepals 2, persistent; petals 5, united below into a short cleft tube. Stamens 3-(6), opp. the 3 smaller petals; style 3-fid. Capsule ± globose, 3-valved, dehiscing explosively; seeds 3, black. Small annual to perennial glab. herbs with opp. lvs. Widespread in temperate to cold regions, with a few not well-defined spp. or of 1 aggregate sp.

2n = 96

Perennial herbs, stoloniferous, forming dense, close-set mats or cushions, often in tufts when growing among other vegetation. Stems and leafy shoots up to 3 mm diam., white, fleshy; procumbent, creeping on or just below the ground; internodes close to distant, rooting at nodes. Leaves alternate, spreading or erect, simple, linear, narrowly lanceolate to elliptic; apex subacute to obtuse, with a single prominent hydathode; petioles indistinct to distinct; margin entire; base membranous, scarious, shortly sheathing, persistent; stomata sparse on adaxial and abaxial surfaces; epidermal cells elongated, mesophyll homocentric. Inflorescences erect, lateral, cymose; peduncle up to 4 cm long; pedicels up to 30 mm long, often recurved after fertilisation; flowers 1–7 per inflorescence. Involucral leaves 2, equal, broadly ovate, apex obtuse, margin membranous, shorter than capsule. Tepals 5, equal, elliptic to obovate, white, sometimes flushed pink, ± patent at anthesis; claw indistinct to distinct, fused at base. Stamens 5, translucent, equal, to ¾ length of tepals, adnate to base of tepals; connective fixed at apex of anther. Anthers ovoid, extrorse, protandrous. Ovary obovoid, with 3 ovules. Style distinct from ovary, with three stigmatic branches, terete, translucent, white or pink; abscising after fertilisation. Stigmatic branches erect and coalescent during male phase, diverging during the female phase; papillae coarse, on adaxial surface only. Capsule ± globose, valves 3, swollen along sutures; valves at maturity dehiscent, dehiscence weakly explosive. Seeds 3 or fewer per capsule, laterally flattened, broadly obovoid; attachment plate small, ± concave with distinct flat strophiole; testa smooth to rugose, cells arranged in regular to irregular pattern, glossy; operculum present. Chromosome number 2n = 96.

Glabrous annual to perennial herbs; rosette usually 0. Stems branching, prostrate to ascending, vegetative and reproductive. Lvs many, decussate. Infl. terminal, often overtopped by vegetative shoot and apparently axillary, racemose, cymose, or reduced to a solitary bracteate fl. Sepals persistent. Petals 5, united at base into a short cleft tube. Stamens 3. Ovary superior, of 3 fused carpels; style branches 3. Ovules 3. Capsule 1-locular, dehiscent by 3 valves. Seeds 3.