Pellaea atropurpurea (L.) Link
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Species Description - Rhizome-scales 3–6 mm, appressed, matted, dull tawny or rusty, the young tips tan and entangled; lvs slightly dimorphic, stiffly erect, mostly 20–40 cm; petiole shorter than the blade, purplish-brown, obviously hairy (as also the rachis) especially on the upper side; pinnae 5–11 pairs, petiolulate, the sterile ones ovate to broadly oblong, the basal mostly at least twice as long as the upper and with 3–15 segments, the ultimate segments mostly 1–7.5 × 0.5–1 cm; fertile segments narrower than the sterile, linear-oblong, acute, mucronate, the irregularly revolute margin opening and commonly leaving many sporangia exposed, eventually becoming flat; 2n=87, an apogamous triploid with 32 spores per sporangium. Calcareous rocks and open woods; s. Que., Vt., and R.I. to Minn. and Wyo., s. to Fla., Ariz., and Mex.; disjunct in Sask., Alta., and B.C. Thought to have originated by hybridization of P. glabella with another undetermined sp.