Notholaena fendleri Kunze, Farrnkräuter 2: 87, plate 136. 1851; Cheilanthes cancellata Mickel; Pellaea fendleri (Kunze) Prantl

Stem scales brown. Leaves 5--25 cm. Petiole dark brown, 0.75--1.5 mm diam. Blade deltate, 4--6-pinnate proximally, leathery to somewhat herbaceous, abaxially covered by whitish farina, adaxially glabrous or glandular; rachis rounded adaxially. Pinna costae distinctly flexuous, branches arising from prominent angles. Ultimate segments not articulate, dark color of stalks continuing into segment bases abaxially; segment margins plane to recurved, often partially concealing sporangia; veins usually obscure adaxially. Sporangia submarginal, borne on distal 1/4 of secondary veins, containing 64 spores. 2 n = 54.

Sporulating summer--fall. Rocky slopes and cliffs; usually on granitic or volcanic substrates; 1700--3000 m; Colo., N.Mex., Wyo.; Mexico in Sonora.

Argyrochosma fendleri is occasionally confused with A . limitanea , which can have slightly flexuous rachises and pinna costae. All A . limitanea specimens with slightly flexuous rachises and costae have 32 spores per sporangium, whereas specimens of A . fendleri consistently have 64. This southern Rocky Mountain species is the only member of the genus that is found on acidic substrates such as granite.