Annual or perennial herbs, usually with a woody base. Stems ± erect or decumbent. Leaves linear, opposite and decussate. Short stemmed leaf fascicles present in the leaf axils, the leaves thus appearing whorled. Stipules scarious, connate. Sepals 5. Petals 5. Stamens 1-10. Styles 3. Capsule dehiscing by 3 valve Seeds often winged.