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..
Ranunculus septentrionalis Poir. in Lam. Encycl. 6: 125. 1804.
Roots simply fibrous; plant branching, 1°-3° high, glabrous, or pubescent, the later branches procumbent and sometimes rooting at the nodes. Leaves large, petioled, 3-divided; divisions mostly stalked, usually cuneate at the base, cleft into broad lobes; lower petioles occasionally a foot long; flowers I' in diameter or more, bright yellow; petals obovate, twice the length of the spreading sepals; head of fruit globose or oval, 4" in diameter; achenes flat, strongly margined, subulate-beaked by the stout sword-shaped style which is of nearly their length and often early deciduous.
Mainly in swamps and low grounds, New Brunswick to Manitoba, Georgia and Kansas. April-July.
R. hispidus Michx. Fl. Bor. Am. 1: 321. 1803.
Usually densely villous when young, sometimes merely appressed-pubescent or glabrate when old; stems ascending or spreading, 8'-2° long; plant not stoloniferous; roots a cluster of thickened fibers. Leaves pinnately 3-5-divided, the divisions ovate, oblong or obovate, narrowed or cuneate at the base, sharply cleft or lobed, usually thin; flowers 6"-18" broad; petals oblong, about twice as long as the spreading sepals, entire or emarginate; head of fruit globose-oval or globose; achenes broadly oval, lenticular, narrowly margined, abruptly tipped by a subulate style of about one-half their length.
In dry woods and thickets, Vermont and Ontario to North Dakota, south to Georgia and Arkansas. The earliest flowering buttercup of the vicinity of New York. Ascends to 6000 ft. in North Carolina. March-May.
Ranunculus fascicularis Muhl. Cat. 54. 1813.
Appressed-pubescent; fibrous roots thickened; plant generally low, 6'-12' high, tufted. Leaves petioled, 3-5-divided; divisions stalked (especially the terminal one), deeply lobed and cleft, the lobes oblong or linear; flowers about 1' broad; petals yellow, obovate-spatulate, much longer than the spreading sepals, rounded, truncate or even emarginate; head of fruit globose, about 4" in diameter; achenes flat, slightly margined, beaked with the subulate persistent style which is nearly or quite their length.
Woods, Ontario to Massachusetts, North Carolina, Wisconsin, Kansas and Texas. Reported from Manitoba. Not common near the Atlantic coast. Bundle-rooted buttercup. Cowslip. April-May.