TORDYLIIUM, HART-WORT, in botany: A genus of plants belonging to the class of pentandria, and order of digynia; and in the natural system arranged under the 45th order, Umbellatae. The corollas are radiated, and all hermaphrodite; the fruit is roundish, and crenated on the margin; the involucre long and undivided. There are seven species; of which two are British, the nodosum and officinale.
1. The nodosum, or knotted parsley, has simple sessile umbels, the exterior seeds being rough. It grows in the borders of corn-fields, and in dry stony places. 2. The officinale, official hart-wort, has partial involucre, as long as the flowers; leaflets oval and jagged; the seeds are large and flat, and their edges notched.