Rhizome short and compactly branched, sclerified, beset with old petiole-bases, the scales 4-6 נ1-1.5 mm, with firm dark midstripe; lvs numerous, tufted, evergreen, firm, with stramineous to greenish petioles, those of the sterile lvs 3-15 cm, those of the fertile lvs longer (to 20+ cm) and nearly or fully equaling the sterile blades; sterile blades 2-11 נ1.5-6 cm, ca thrice pinnate, with ±rounded, toothed ultimate segments to 8 נ4 mm; fertile blades 4-14 נ1.5-5 cm, 2-3 times pinnate, the ultimate segments linear or linear-oblong, 4-12 נ1-2 mm, the margins broadly reflexed but not much modified, tending to open out as the sporangia mature; sori eventually covering the whole lower surface of the pinnule; 2n=60 (Amer. pls). Rock crevices; Que. to Alas., s. to n. Mich., ne. Minn., and N.M.; Eurasia. The Amer. pls are var. acrostichoides (R. Br.) C. B. Clarke. (C. a.)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.