Petiole 10--100 cm. Blade ovate-triangular to nearly pentagonal, 3-pinnate to 3-pinnate-pinnatifid, 30--200 × 15--100 cm; blades, rachises, and costae usually densely covered abaxially with abundant, contorted, lax, spreading hairs. Pinnae (proximal) triangular, distal pinnae oblong; terminal segment of each pinna ca. 4 times longer than wide, longer ultimate segments less than their width apart, ca. 1.5--5 mm wide. Pinnules at nearly 90° angle to costa; fertile ultimate segments adnate or equally decurrent and surcurrent. Outer indusia entire, pilose on margin and surface, hairs like those of axes. In dry to moist woods and open areas in partial to full sun, forming abundant colonies; 0--3000 m; Alta., B.C.; Alaska, Ariz., Calif., Colo., Idaho, Mont., Nev., N.Mex., Oreg., S.Dak., Tex., Utah, Wash., Wyo.; Mexico in Baja California, Chihuahua, and Durango.
Lvs ±densely short-hairy, the reflexed indusial margin also ciliate; pinnules nearly at right angles to the costa; cordilleran region of w. N. Amer., and locally in n. Mich., s. Ont. and s. Que.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
