Herbs, annual, of marshes, with milky juice. Leaves petiolate, elliptic to elliptic-lanceolate. Scapes erect; umbels terminal; bracts forming an involucre. Pedicels slender. Sepals persistent, green, margin membranous. Petals white. Stamens usually 8 or 9, free. Carpels 6-9, 1-whorled. Follicles with a short beak. Seeds strongly curved; embryo horseshoe-shaped.