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..
Perennial subscapose glabrous herbs, with thick roots', pinnately decompound leaves, and white flowers (in our species) in peduncled umbels. Involucre of several bracts or none. Involucels of 1 to numerous bracts. Calyx-teeth rather prominent. Petals inflexed at the apex. Stylopodium depressed. Fruit globose, ovoid or ellipsoid, flattened laterally or not at all. Carpels dorsally flattened, with 3-5 flat equal wings; oil-tubes several or solitary in the intervals, few or several on the commissural side. [Greek, wave-winged, referring to the fruit.]
About 13 species, natives of western and central North America, the following typical.
Cymopterus acaulis Rydberg, Bot. Surv. Neb. 3: 38. 1894.
Low, the stem seldom over 1' high. Leaves erect or ascending, bright green, 3'-8' long, slender-petioled, pinnate or bipinnate into linear-oblong obtuse entire or lobed segments; umbels slender-peduncled, compact, 1' or less broad, several-rayed; rays only 1"-2 1/2" long; pedicels very short; involucre none; involucel of a single palmately-lobed bractlet; fruit broadly oval, about 3" in diameter when mature; oil-tubes 4-5 in the intervals; seed-face nearly flat.
In dry soil, Minnesota, Wisconsin and Iowa to Arkansas, Assiniboia, British Columbia and Colorado. April-May.