10. Pellaea mucronata (D. C. Eaton) D. C. Eaton in Emory, Rep. U.S. Mex. Bound. 2(1): 233. 1859.
Allosorus mucronatus D. C. Eaton, Amer. J. Sci. Arts 22: 138. 1856; Pellaea ornithopus Hooker
Stems compact, ascending, stout, 5--10 mm diam.; scales bicolored, linear-subulate, 0.1--0.3 mm wide, centers black, thick, margins brown, thin, erose-dentate. Leaves monomorphic, clustered on stem, 7--45 cm; croziers sparsely villous. Petiole dark brown, lustrous, flattened to slightly grooved adaxially, without prominent articulation lines. Blade ovate-deltate, (2--)3-pinnate proximally, 4--18 cm wide; rachis brown throughout, straight, shallowly grooved adaxially, usually glabrous. Pinnae perpendicular to rachis to strongly ascending, not decurrent on rachis, usually with 9--40 ultimate segments; costae straight, 10--70 mm, much longer than ultimate segments. Ultimate segments narrowly oblong, 2--12 mm, leathery, glabrous; margins recurved to strongly revolute on fertile segments, usually covering more than 1/2 abaxial surface, borders greenish, usually dentate; apex mucronate. Veins of ultimate segments obscure. Sporangia short-stalked, containing 64 spores, intermixed with abundant farina-producing glands.
Pellaea mucronata encompasses two morphologic extremes that tend to occupy different habitats and are treated here as subspecies. The typical 3-pinnate form ( P . mucronata subsp. mucronata ) is scattered throughout California and southern Nevada, usually below 1800 m elevation. The 2-pinnate form with ascending, overlapping pinnae ( P . mucronata subsp. californica ) is apparently confined to the Sierra Nevada and Transverse Ranges of California at elevations greater than 1800 m. The taxonomic status of these entities remains in dispute, and they are often treated as mere ecological forms. W. H. Wagner Jr. et al. (1983) indicated that natural hybrids formed between P . bridgesii and these two taxa are morphologically distinct, suggesting that the differences observed between the subspecies of P . mucronata are genetically based. In addition to P . bridgesii , subsp. mucronata apparently hybridizes with both P . truncata and P . brachyptera (see comments under those species).