8. Cheilanthes covillei Maxon, Proc. Biol. Soc. Wash. 31: 147. 1918.
Coville's lip fern
Myriopteris covillei (Maxon) A. Löve & D. Löve
Stems short-creeping, usually 2--4 mm diam.; scales usually uniformly dark brown to black or rarely with narrow, light brown margins, linear-lanceolate, straight to slightly contorted, strongly appressed, persistent. Leaves clustered, 5--30 cm; vernation noncircinate. Petiole dark brown, rounded adaxially. Blade lanceolate to ovate-deltate, 3--4-pinnate at base, 1.5--5 cm wide; rachis rounded adaxially, somewhat scaly, not pubescent. Pinnae not articulate, dark color of stalk continuing into pinna base, basal pair not conspicuously larger than adjacent pair, usually equilateral, appearing glabrous (or somewhat scaly) adaxially. Costae green adaxially for most of length; abaxial scales multiseriate, ovate-lanceolate, deeply cordate at base, with overlapping basal lobes, conspicuous, the largest 0.4--1.5 mm wide, strongly imbricate, usually concealing ultimate segments, ciliate only on basal lobes. Ultimate segments round to oblong, beadlike, the largest 1--3 mm, abaxially glabrous or with a few small scales near base, adaxially glabrous. False indusia marginal, weakly differentiated, 0.05--0.25 mm wide. Sori ± continuous around segment margins. Sporangia containing 64 spores. 2 n = 60.
Sporulating late spring--fall. Rocky slopes, cliffs, and ledges, usually on igneous substrates; 100--2500 m; Ariz., Calif., Nev., Utah; Mexico in Baja California.
Cheilanthes covillei can be difficult to distinguish from the closely related C . intertexta and C . clevelandii ; it differs from these two species in having glabrous blades and costal scales ciliate only on the basal lobes. Cheilanthes covillei is occasionally misidentified as C . fendleri because the cilia of the scales are often obscure; it is distinguished from the latter species by having rigid, dark brown stem scales that are strongly appressed. Cheilanthes covillei hybridizes with C . parryi and C . newberryi to form rare, sterile diploids known as C . × parishii Davenport and C . × fibrillosa (Davenport) Davenport ex Underwood, respectively. A third sterile diploid hybrid with C . fendleri has recently been discovered in central Arizona (M. D. Windham, unpublished).