Sp. Pl. 2: 1082. 1753.
Roots not proliferous. Stems short-creeping or ascending, frequently branched; scales dark reddish brown to blackish throughout, narrowly deltate, 2–4 × 0.2–0.4 mm, margins entire to undulate or with widely spaced shallow teeth. Leaves monomorphic. Petiole reddish brown at base, green distally, lustrous, 1–5(–6) cm, 1/4–1/2(–1) times length of blade; indument of dark reddish brown to black, narrowly deltate scales grading into glandular hairs. Blade linear, 1-pinnate throughout, 2–13 × 0.6–1.2 cm, thin, glabrous or with sparse minute hairs; base slightly tapering or truncate; apex acute, not rooting. Rachis green throughout, dull, glabrous or with scattered hairs as on petioles. Pinnae in 6–21 pairs, deltate to rhombic; medial pinnae 5–6 × 4–5 mm; base obtuse and often inequilateral; distal margins crenate; apex rounded to acute. Veins free, evident. Sori 2–4 pairs per pinna, on both basiscopic and acroscopic sides. Spores 64 per sporangium. 2n = 72.
Habitat: Limestone and other basic rocks
Elevation: 0–4000 m
Greenland, Alta., B.C., N.B., Nfld. and Labr. (Nfld.), N.W.T., N.S., Ont., P.E.I., Que., Yukon, Alaska, Calif., Colo., Idaho, Maine, Mich., Mont., Nev., N.Y., Oreg., S.Dak., Utah, Vt., Wash., Wis., Wyo.
Hybridization between Asplenium trichomanes-ramosum and A. trichomanes produces the fertile allotetraploid A. adulterinum, which occurs on Vancouver Island.