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..
Thalictrum clavatum DC. Syst. 1: 171. 1818.
Glabrous, branching, 6'-24' high. Leaves basal and cauline, biternate; leaflets oval, ovate, or the terminal obovate-cuneate, thin, pale beneath, stalked, with 3 main lobes and a few secondary ones, their margins not revolute; inflorescence cymose; flowers perfect; filaments clavate and petal-like; anthers oblong, blunt; achenes spreading, equalling their stipes or longer, obliquely oblong, narrowed at each end, flattened; stigma minute.
Thalictrum dioicum var. coriaceum Britton, Bull. Torr. Club 18: 363. 1891.
Tall, 3°-5° high, the large rootstocks and roots bright yellow. Stem striate, panicu-lately branched above; leaves 3-4-ternate, short-petioled, the lower petioles expanded at the base into stipule-like appendages; leaflets obovate or reniform-orbicular, coriaceous, nearly white beneath, usually deeply and sharply incised, the veins prominent on the lower surface; flowers dioecious, the staminate nearly white, the anthers linear, subulate-tipped, longer than the filiform filaments; pistillate flowers purple; achenes oblong-ovoid, subacute, stalked, sharply ribbed, somewhat longer than the persistent style.
Thalictrum caulophylloides Small, Bull. Torr. Club 25: 136. 1898.
Tall, 2 1/2°-5 1/2° high, the creeping rootstocks and the roots, pale. Stem finely striate, rather widely branched above; leaves 3-4-ternate, very short-petioled, with the stipular appendages smaller than in T. coriaceum; leaflets thinnish, but firm, broadly oval, suborbicular or somewhat reniform in outline, larger than in T. coriaceum, the terminal ones wider than long, all 3-5-lobed, pale or glaucous beneath; flowers dioecious, the staminate greenish, the anthers narrowly linear, larger, longer- and more slender-tipped than in T. coriaceum; pistillate flowers greenish-purple; achenes elliptic, acute, decidedly stalked, sharply ridged, much longer than the persistent style.
On mountain sides and river banks, Maryland and Virginia near the District of Columbia and in eastern Tennessee. May-July.