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..
Aquatic or partly emersed, branching, sometimes several feet long. Immersed leaves repeatedly divided into capillary segments, short-petioled, 1'~3' long; emersed leaves glabrous or pubescent, 1/2'-2' broad, petioled or the upper nearly sessile, 3-5-di-vided, the divisions cleft into linear or cuneate segments; flowers yellow, 3"-18" broad; petals 5-8, much longer than the sepals; head of fruit globose or oblong, 3"-5" long; achenes less than 1" long, callous-margined, at least toward the base, tipped with a straight persistent beak of one-half their length or more.
Perennial, floating or creeping, usually pubescent at least on the younger parts, sometimes densely so; stems slender, often rooting from the lower nodes, 2'8' long. Leaves slender-petioled, orbicular or reniform in outline, 1/4'-1' wide, palmately divided nearly to the base into obtuse lobes or segments; flowers yellow, long-peduncled, 2"-7" broad; sepals spreading, ovate, obtusish, early deciduous; petals about 5; head of fruit subglobose or ovoid-oblong, obtuse, 2"-3" long; achenes little compressed, smooth, not margined, i" long, acutish on the back, abruptly tipped with a slender style of about one-third their length.
In moist soil, Nova Scotia to Alaska, Michigan, North Dakota, south in the Rocky Mountains to New Mexico and Utah. July-Aug.
Ranunculus hyperboreus Rottb. Skrift. Kjoeb. Selsk. 10: 458. 1770.
Stem slender, glabrous, filiform, creeping, 2'-6' long. Leaves petioled, 3-lobed or cleft, broadly ovate, 2"-$" broad, 2"-4" long, obtuse, the base cuneate or rounded, the lobes oblong, obtuse, the lateral ones sometimes toothed; petioles sheathing and biauriculate; flowers few, 2"-3" broad, yellow; petals slightly shorter than the reflexed sepals; peduncles 4"-6" long; head of fruit globose, 2" broad; achenes slightly compressed, with a minute blunt point.