13. Cheilanthes yavapensis T. Reeves ex Windham, Contr. Univ. Michigan Herb. 19: 32. 1993.
Yavapai lip fern
Stems long-creeping, 1--3 mm diam.; scales often bicolored, with broad, poorly defined, dark, central stripe and narrow, brown margins, lanceolate, straight to slightly contorted, strongly appressed, persistent. Leaves scattered, 7--35 cm; vernation noncircinate. Petiole dark brown, rounded adaxially. Blade oblong-lanceolate to nearly ovate, 4-pinnate at base, 2--6 cm wide; rachis rounded adaxially, with scattered linear-lanceolate scales and sparse monomorphic pubescence. Pinnae not articulate, dark color of stalk continuing into pinna base, basal pair not conspicuously larger than adjacent pair, usually equilateral, appearing sparsely pubescent adaxially. Costae green adaxially for most of length; abaxial scales multiseriate, lanceolate, truncate to cordate at base, without overlapping basal lobes, conspicuous, the largest 0.4--1 mm wide, strongly imbricate, often concealing ultimate segments, ciliate, cilia coarse, usually distributed entire length of scale. Ultimate segments round to oblong, beadlike, the largest usually 1--2 mm, abaxially glabrous or with a few small scales near base, adaxially appearing sparsely pubescent but actually nearly glabrous. False indusia marginal, weakly differentiated, 0.05--0.25 mm wide. Sori ± continuous around segment margins. Sporangia containing 32 spores. n = 2 n = 120, apogamous.
Sporulating summer--fall. Rocky slopes and ledges, usually on igneous substrates; 500--2400 m; Ariz., N.Mex., Tex.
Cheilanthes yavapensis is an apogamous tetraploid, apparently formed by hybridization between C . lindheimeri and C . covillei (G. J. Gastony and M. D. Windham 1989). Although C . yavapensis has long been included within the concept of C . wootonii , the discovery that the similarities resulted from hybrid convergence rather than common ancestry requires that they be recognized as two distinct species. Unfortunately, the morphologic characteristics that separate these taxa are subtle, and careful study will be necessary to determine the proper dispositon of problematic specimens. In addition to the characteristics mentioned in the key, C . yavapensis is distinguished from C . wootonii by having larger spores, averaging more than 62 µm in diameter.