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 obtusiusculus Raf. Med. Rep. (II.;
5: 359. 1808. Ranunculus alismaefolius A. Gray, Man. Ed.
5, 41. 1867. Not Geyer, 1848. Ranunculus ambigens S. Wats. Bibliog. Index 1: 16. 1878.
Mostly stout and 1°-3° high, ascending, glabrous, rooting from the lower nodes; stem hollow, sometimes nearly 1' thick at the base. Leaves lanceolate or oblong-lanceolate, 3'-6' long, 5"-12" wide, denticulate or entire, all but the uppermost on broad petioles, which clasp the stem by a broad base; flowers yellow, panicled, 6"-8" broad; petals 5-7, much exceeding the sepals; head of fruit globose or slightly elongated, 5"-6" in diameter; achenes compressed, \" long, subulate-beaked, but the beak early deciduous.
Marshes, Maine and Ontario to Georgia, Tennessee, Minnesota and Arkansas. June-Aug.
Ranunculus nivalis L. Sp. Pl. 553. 1753.
Stem simple, 4'-12' high. Basal leaves long-petioled, 3-7-lobed, or crenate, thick, glabrous, the blade about 1' broad, those of the stem short-petioled or sessile, deeply lobed; flowers solitary, 6"-9" broad, white or light yellow; calyx nearly half the length of the petals, densely black or brown hairy all over, as is the upper part of the peduncle; head of fruit oblong, 6" long; achenes tipped with the subulate style.
Ranunculus pygmaeus Wahl. Fl. Lapp. 157. 1812.
Small, 1'-2' high, glabrous or sparsely pubescent. Basal leaves slender-pelioled, deeply 3-5-lobed or divided, the blade 3"-6" wide; those of the stem similar and nearly sessile; flowers yellow, 2"-3" wide, the petals slightly exceeding the glabrous or slightly pubescent sepals; head of fruit short-oblong, 2" long; achenes 1/2" long, lenticular, tipped with a slender beak.
Quebec, Labrador, arctic America, and in the Rocky Mountains. Also in Europe and Asia.
Ranunculus Sabini R. Br. is another arctic and Rocky Mountain species, differing from this by larger flowers and densely pubescent sepals.
Ranunculus pedatifidus J. E. Smith in Rees' Cyclop, no. 72. 1813-16.
R. affinis R. Br. in Parry's Voy. App. 265. 1823.
Erect, 4'-12' high, branching. Basal leaves peti-oled, broadly ovate or nearly orbicular, about 1' broad, obtuse, irregularly deeply cleft, those of the stem deeply lobed, nearly sessile, the lobes narrow; flowers yellow, 4"-6" broad, the petals exceeding the spreading pubescent calyx; head of fruit oblong, 3"-6" long; achenes oval, tipped with a short beak, often hairy.
Labrador to Alaska, south in the Rocky Mountains to Arizona. Also in northern Asia. Rough-fruited crowfoot. Summer.