This section is from the book "An Illustrated Flora Of The Northern United States, Canada And The British Possessions Vol2", by Nathaniel Lord Britton, Addison Brown. Also available from Amazon: An Illustrated Flora of the Northern United States, Canada and the British Possessions. 3 Volume Set..
An annual glabrous herb, with pinnately dissected somewhat shining leaves, and compound umbels, both terminal and opposite the leaves. Involucre none, or of a single bract. Bracts of the involucels 1-5, setaceous, turned to one side. Calyx-teeth obsolete. Petals inflexed at the apex. Stylopodium broad, thick. Fruit globose-ovoid, glabrous. Carpels dorsally compressed, the 5 ribs prominent, corky, acute, nearly equal; oil-tubes solitary in the intervals, 2 on the commissural side. Seed-face flat. [Greek, burning, from the shining foliage.]
A monotypic genus of Europe and Asia.
Aethusa Cynapium L. Sp. Pl. 256. 1753.
Erect, leafy, dichotomously branched, rather slender, 1°-2 1/2° high. Leaves 2-3-pinnate, the lower slender-petioled, the upper nearly sessile; petiole-bases dilated; ultimate segments linear, acutish; umbels long-peduncled, 2'-3' broad in fruit, 8-12-rayed; rays 1/2-1 1/2' long; pedicels 1"-4" long; bractlets of the involucels 2-4, linear, turned downward; fruit about 1 1/2" long, somewhat longer than broad; flowers white.