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..
Slender glabrous herbs, with ternately decompound leaves, and solitary or panicled white flowers. Sepals 5 or 6, petaloid, deciduous. Petals 5, nectariform or none. Stamens numerous. Carpels 2-20, sessile (stalked in a western species), several-ovuled, forming a head of follicles in fruit. [Old Greek name for some Fumaria.]
A genus of about 15 species, natives of the north temperate zone. Besides the following, there are 3 other North American species, natives of the Pacific Coast. Type species: Isopyrum rhalictroides L.
Slender, erect, paniculately branching above; roots fibrous and sometimes tuberiferous. Basal leaves long-petioled, biternate, thin, the ultimate segments broadly obovate, obtuse, lobed or divided; upper ones similar but sessile or short-petioled; flowers several, terminal and axillary, white, $"-9" broad; sepals 5, oblong or somewhat obovate, obtuse; petals none; stamens many; filaments slender, white, thickened above; carpels few; follicles widely spreading,, ovate, 2" long, several-seeded, tipped with a beak nearly one-half their length.
In moist woods and thickets, Ontario to Minnesota, Kansas, Florida and Texas. May.