Lvs clustered, 6-12(-16) dm; petiole densely woolly when young; blade pinnate-pinnatifid, dimorphic, the sterile ones oblong, to 3 dm wide, relatively firm, shining green, gradually tapering to the tip, as also the individual pinnae; pinnae oblong-lanceolate, sessile, 15-25 pairs, alternate or subopposite, to 15 נ3 cm, with a tuft of brownish hairs at the base, deeply pinnatifid, the segments 15-20 on a side, alternate, broadly oblong, obtuse or subacute, usually entire, laxly ciliate, the veins 9-12 pairs per segment; fertile lvs vernal, central, surrounded by the larger sterile outer ones, soon withering brown, essentially bipinnate, the rachis long-woolly, the pinnae 2-4 cm נ8-15 mm; sporangia cinnamon-brown; 2n=44. Swamps, streambanks, and other moist places in subacid soil; Lab. to Minn., s. to Fla., Tex., N.M., and trop. Amer.; e. Asia. Ours is var. cinnamomea.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.