Cystopteris fragilis (L.) Bernh.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Species Description - Lvs glabrous or inconspicuously glandular, in a small cluster on a short, densely scaly rhizome, 0.5–3.5(–4) dm, the dark brown (or distally greenish) petiole shorter than or to as long as the blade; blade mostly 3.5–20(–25) × 1.5–8 cm, (2–)2.5–4(–5) times as long as wide, 2–3 times pinnate, with 8–18 pairs of pinnae (the members of a pair often offset, especially the distal pairs), the lowest pair equaling or generally a little smaller than the next pair, the upper ones gradually reduced so that the blade tapers into a narrow tip; veins typically directed to the teeth of the pinnules, but the tooth sometimes apically slightly indented so that the vein ends in a small sinus; indusium pale, not glandular; 2n=188 in ours. Moist, mostly wooded slopes and ledges in circumneutral soil; circumboreal, s. in our range to Va. and Mo.