Palmer's spleenwort

Roots not proliferous. Stems short-creeping, unbranched; scales black with lighter margins, linear-lanceolate, 1.5--3 × 0.1--0.4 mm, margins entire. Leaves monomorphic. Petiole purplish black, lustrous, 0.5--3 cm, 1/3--1/20 length of blade; indument of black filiform scales at base. Blade linear, 1-pinnate throughout, 7--17.5 × 0.9--1.8 cm, thick, glabrous; base gradually reduced; apex gradually reduced to whiplike rooting tip. Rachis purplish black throughout, lustrous, glabrous or nearly so. Pinnae in (12--)20--40 pairs, oblong; medial pinnae 6--9 × 3--4 mm; base broadly cuneate or auriculate; margins crenate-serrate; apex obtuse. Veins free, obscure. Sori 3--7 pairs per pinna, on both basiscopic and acroscopic sides. Spores 64 per sporangium.

Shaded rocky slopes, wet ledges, often in protected places; 900--2000(--2750) m; Ariz., N.Mex., Tex.; Mexico; Central America in Guatemala, Belize.