Mrs. Cooper's lip fern

Stems compact to short-creeping, usually 4--8 mm diam.; scales brown at base and darker toward tip, linear-subulate, straight to slightly contorted, loosely appressed, persistent. Leaves clustered, 5--30 cm; vernation circinate. Petiole dark brown, flattened or slightly grooved distally on adaxial surface. Blade linear-oblong to lanceolate-ovate, 3-pinnate at base, 1.5--5 cm wide; rachis flattened or slightly grooved adaxially, lacking scales, with monomorphic pubescence. Pinnae not articulate, dark color of stalk continuing into pinna base, basal pair slightly smaller than adjacent pair, ± equilateral, appearing hirsute adaxially. Costae green adaxially for most of length; abaxial scales absent. Ultimate segments linear-oblong to ovate, not beadlike, the largest 3--5 mm, abaxially and adaxially hirsute with long, strongly flattened hairs. False indusia marginal, weakly differentiated, 0.05--0.25 mm wide. Sori usually discontinuous, concentrated on apical and lateral lobes. Sporangia containing 64 spores. 2 n = 60.

Sporulating late spring--summer. Calcareous cliffs and ledges; usually on limestone; 100--700 m; Calif.

Although scattered throughout much of California, Cheilanthes cooperae is apparently rare and quite localized. It appears to be most closely related to C . viscida , from which it differs in lacking glandular pubescence. The ranges of the two species do not overlap, and they seem amply distinct.