Clonal, with deep-seated long-creeping black rhizomes as well as erect leafy crowns; sterile lvs 0.5-2(-3) m, short-petiolate; blade ±hairy along the rachis and costae, oblanceolate, 1.5-5 dm wide, pinnae numerous, alternate, gradually reduced toward the base of the blade, more abruptly so upwards, long-acuminate, deeply pinnatifid with 20+ pairs of segments, these pinnately open-veined, oblong, obtuse, with slightly revolute, crenulate margin; fertile lvs produced from midsummer to early fall, not over 7 dm, the numerous pinnae 2-6 cm נ2-4 mm, obtuse, their numerous, crowded pinnules hooded; 2n=80. Swamps and moist woods in circumneutral soil; circumboreal, in Amer. s. to Va., Mo., S.D., and B.C. (M. pensylvanica; Pteretis nodulosa)

Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.

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Varieties 2 (1 in the flora): North America, Eurasia.