Rio Grande scaly polypody

Polypodium thyssanolepis A. Braun ex Klotzsch var. riograndense T. Wendt, Amer. Fern J. 70: 6. 1980

Stems short-creeping, sparingly branched, 2--3 mm diam.; scales subulate to lanceolate-acuminate, centrally clathrate with cell luminae large and clear, surfaces glabrous, margins lacerate-ciliate. Leaves to 20 cm, strongly hygroscopic. Petiole grooved, otherwise round in cross section, sparsely scaly; scales rarely overlapping, margins denticulate to ciliate. Blade triangular-oblong to ovate, deeply pinnatifid, to 5 cm wide, moderately scaly abaxially, glabrous adaxially; scales concolored to obscurely bicolored, usually dark reddish brown throughout, broadly ovate-lanceolate, clathrate, more than 0.5 mm wide, margins fringed-ciliate. Venation mostly free with occasional areoles, never more than 1 included veinlet in fertile areoles. Sori round, discrete, surficial to shallowly embossed, soral scales attached at periphery of receptacle. Spores smooth with scattered spheric deposits on surface, 60--74 µm. 2 n = 148.

Sporulating summer--fall. Growing on rocky slopes and ledges, and in crevices, usually in moist, shaded canyons; 1500--2500 m; Ariz., Texas; n Mexico.

In the past Pleopeltis riograndensis has been treated as a variety of P . thyssanolepis , but it differs from the latter species in that the petiole and leaf are only sparsely scaly rather than densely so, the blade scales are mostly ovate or ovate-lanceolate rather than nearly spheric, the venation is mostly free rather than mostly areolate, and the basal segments of the blade are alternate rather than opposite to nearly opposite.