Leaves alternate, no stipules (except for Hydrocotyle vulgaris). Flowers small, 5-petalled, in umbels, usually in turn arranged in an umbel. The whole flowerhead thus looks like a flat opened umbrella, whose spokes (rays) are the stalks of the secondary umbels. Flowers of white-flowered species often tinged pink. The strap-like upper and lower bracts at the base at the primary and secondary umbels respectively, and the dry usually ridged fruit, are both important in identification.