Adiantum cordifolium Sessé & Mociño, Naturaleza (Mexico City), ser. 2, 1(App.): 182. 1890; Pellaea cardiomorpha Weatherby; P. sagittata (Cavanilles) Link var. cordata (Cavanilles) A. F. Tryon

Stems compact, ascending, stout, 6--10 mm diam.; scales uniformly orange-brown and thin, lanceolate to ovate, largest scales 0.3--1 mm wide, margins dentate. Leaves somewhat dimorphic, sterile leaves shorter than fertile leaves, clustered on stem, 15--50 cm; croziers not conspicuously pubescent, densely scaly. Petiole straw-colored, tan, or gray, not lustrous, rounded or slightly flattened adaxially, without prominent articulation lines. Blade ovate-deltate, 2-pinnate proximally, 5--20 cm wide; rachis tan throughout, straight to slightly flexuous, rounded or flattened adaxially, glabrous. Pinnae perpendicular to rachis or slightly ascending, not decurrent on rachis, usually with 3--15 ultimate segments; costae straight to slightly flexuous, 25--100 mm, longer than ultimate segments. Ultimate segments round-cordate to deltate-cordate, 5--15 mm, herbaceous to leathery, glabrous or puberulent; margins recurved on fertile segments, covering less than 1/2 abaxial surface, borders whitish, crenulate; apex rounded or retuse. Veins of ultimate segments usually evident. Sporangia short-stalked, containing 64 spores, not intermixed with farina-producing glands. 2 n = 58.

Sporulating summer--fall. Rocky slopes and ledges, usually on volcanic substrates; 1000--2500 m; Tex.; Mexico.

The diploid Pellaea cordifolia has often been treated as a variety of the Central American and South American apogamous triploid, P . sagittata . The two taxa are distinguished by a number of qualitative morphologic features (A. R. Smith 1980), and it seems unlikely that they represent cytotypes of a single species. A. F. Tryon (1957) suggested that P . sagittata may have originated through hybridization between P . ovata and P . cordifolia (as P . sagittata var. cordata ).