Linnaea 9: 67. 1834.
Roots not proliferous. Stems erect or ascending, rarely branched; scales black throughout, linear-lanceolate, 2–3 × 0.2–0.4 mm, margin entire, apex attenuate. Leaves monomorphic. Petiole black or purplish black throughout, lustrous, 0.3–5 cm, 1/4–1/15 length of blade; indument of black filiform scales at base. Blade linear or narrowly oblanceolate, 1-pinnate throughout, 6–22(–37) × 1–1.8(–2.3) cm, thin, glabrous; base tapered; apex acute, not rooting. Rachis black throughout, lustrous, glabrous. Pinnae in 15–40 pairs, oblong; medial pinnae somewhat asymmetric, oblong, 4–10 × 2–4(–5) mm; base acute, acroscopically enlarged; margins serrate to crenate, lobed; apex obtuse. Veins free, evident. Sori 3–6 pairs per pinna, on both basiscopic and acroscopic sides of pinnae. Spores 64 per sporangium. 2n = 144, 216.
Habitat: Sinkholes, limestone rocks in shady hammocks, masonry
Elevation: 0–50 m
Fla., Ga., Mexico, West Indies in Cuba, Puerto Rico, Bermuda, Central America in Belize.
The tetraploid cytotype (4 x) of Asplenium heterochroum hybridizes with A. resiliens (3 x) to produce A. × heteroresiliens (5 x). It is extremely rare and local, known in northern peninsular Florida from Alachua, Citrus, Columbia, Jackson, and Marion counties.