Rhizomes slender, creeping, black, shiny, apex clothed with brown ovate-lanceolate scales. Fronds distant; fertile lamina (15-)20-30(-50) cm; stipe stramineous, 10-22(-35) cm, slender, with sparse scales at base; lamina nearly tripartite, usually 2-pinnate-pinnatifid, pentagonal-ovate or broadly ovate-triangular, 7-15(-20) cm long and wide, thinly herbaceous or submembranous, base broadly cuneate, apex acuminate; basal pair of pinnae nearly as large as other portion of lamina, narrowly triangular, (3.5-)5-9(-12) × 2.5-4(-7) cm, pinnate-pinnatifid, base subtruncate, with stalk (0.8-)1-1.5(-2.5) cm, portion of rachis between basal pinnae and central lamina ca. 3 cm; pinnules 5 or 6 pairs, oblong-lanceolate, 1.5-2(-4) × 0.5-2 cm, base rounded-cuneate, sessile, apex acute or acuminate, opposite or subopposite, spreading; largest pinnules with 6-10 pairs of segments, segments approximate, oblong to narrowly ovate, ca. 4 mm, lobed to narrow costular wing, entire to shallowly lobed at margin, rounded-obtuse at apex; second basal pair of pinnae 1.5-4 cm apart from basal pair, sometimes shortly stalked, upper pinnae sessile; veins pinnate in segment, simple, oblique, visible abaxially; rachis and costae slender, eglandular. Sori small, exindusiate, orbicular, abaxial on veins. Spore wall surface rugate, foveolate. 2n = 160.
Stems 0.5--1.5 mm diam.; scales 1--4 mm. Fertile leaves usually 12--42 cm. Petiole 9--28 cm, with sparse glandular hairs distally; scales 2--6 mm. Blade broadly deltate, 2-pinnate-pinnatifid, 3--14 cm, lax and delicate, abaxial surface and rachis glabrous or with sparse glandular hairs, adaxial surface glabrous. Pinna apex entire, rounded. Proximal pinnae 2--12 cm, ± perpendicular to rachis, with basiscopic pinnules ± perpendicular to costa; basal basiscopic pinnule usually sessile, pinnatifid or rarely pinnate-pinnatifid, if sessile then with basal basiscopic pinnulet often equaling or longer than adjacent pinnulet; 2d basal basiscopic pinnule sessile, with basal basiscopic pinnulet equaling or longer than adjacent pinnulet; basal acroscopic pinnule sessile, with basal basiscopic pinnulet longer than or equaling adjacent pinnulet. Pinnae of 2d pair usually sessile with basal basiscopic pinnule longer than or equaling adjacent pinnule and about equal to basal acroscopic pinnule; basal acroscopic pinnule equaling or slightly shorter than adjacent pinnule, often with entire, rounded apex. Pinnae of 3d pair sessile with basal basiscopic pinnule equaling adjacent pinnule and equaling basal acroscopic pinnules; basal acroscopic pinnule equaling or slightly shorter than adjacent pinnule. Ultimate segments of proximal pinnae oblong, entire to crenate, apex entire, rounded. Spores 34--39 µm. 2 n = 160.
"Petiole 10–30 cm; blade yellow-green, scaleless, deltoid-pentagonal, to 18 × 25 cm, bipinnate-pinnatifid to tripinnate-pinnatifid, glabrous or occasionally slightly glandular especially along the rachis, pinnae several pairs, opposite, the members of the lowest pair deltoid and each nearly as long as the rest of the blade, with a petiolule to 2.5 cm long, distinctly asymmetrical, the lowest basiscopic segment evidently the largest, mostly a third as long as the main rachis or longer; ultimate segments oblong, 8–18 mm, obtuse, the margins crenate to subpinnatifid, not recurved; veins 2–6 pairs, mostly simple; 2n=160 (ours). Cool woods and talus-slopes; circumboreal, s. to Va., N.C., O., Ill., Io., and Ariz. A vegetatively reproducing hybrid with the next is G. ×heterosporum W. H. Wagner."
|Common oak fern, gymnocarpe fougère-du-chêne|