13.
Thalictrum venulosum
Trelease, Proc. Boston Soc. Nat. Hist. 23: 302. 1886.
Veiny meadow-rue, early meadow-rue
Stems erect, 20-50 cm, glabrous, from rhizomes. Leaves basal and cauline; cauline 1-3, those proximal to inflorescence petiolate, those subtending panicle branches sessile. Leaf blade 3-4×-ternately compound; leaflets obovate to orbiculate, apically 3-5-lobed, 5-20 mm, lobe margins crenate, surfaces abaxially glabrous or glandular-puberulent. Inflorescences terminal, panicles, narrow and dense, many flowered. Flowers: sepals greenish white, lanceolate or broadly ovate to elliptic or obovate, 2-4 mm; filaments colored, not white, (1.8-)3-5.5 mm; anthers 2-3.5 mm, blunt to mucronate; stigma commonly yellowish. Achenes 5-17, erect to spreading, not reflexed, nearly sessile; stipe 0.1-0.3 mm; body often distinctly curved, elliptic-oblong, nearly terete to slightly flattened, adaxial surface 3-4(-6) mm, glabrous to glandular, veins distinct, not anastomosing-reticulate; beak 1.5-2.5(-3) mm.
Flowering early summer-mid summer (Jun-Aug). Prairies, riparian woods, and coniferous, deciduous, and mixed forests; 600-3700 m; Alta., B.C., Man., N.W.T., Ont., Que., Sask., Yukon; Colo., Idaho, Minn., Mont., Nebr., Nev., N.Mex., N.Dak., Oreg., S.Dak., Utah, Wash., Wis., Wyo.
Thalctrum venulosum is similar to T . confine and T . occidentale . Careful field studies are needed to clarify the relationships among these taxa.
