Small annual or perennial herbs. Leaves linear to subulate, opposite, ± connate. Flowers solitary or in few-flowered cymes, (solitary-2 in our species). Sepals 4-5, free. Petals 4-5, free, often minute or sometimes absent. Stamens 10(-5). Styles 4-5. Fruit a capsule, dehiscing to the base by 4-5 valves. Seeds minute, numerous.