Rio Grande Scaly Polypody

Description

Usually growing on rocky soil or in crevices; rhizomes slender, short-creeping, somewhat branched, scaly, the scales tan marginally with black centers; leaves monomorphic, closely spaced; leaf blades deeply 1-pinnatifid, the basal segments alternate, oblong to narrowly triangular in outline, to 20 cm long and 4 cm wide, subcoriaceous, strongly hygroscopic, glabrous on upper surface, the venation mostly free, sparsely scaly on lower surface with scattered to only slightly overlapping scales (blade surface not concealed), the scales ovate to ovate-lanceolate, distinctly clathrate (= net- or lattice-like in appearance) under magnification; sori round, not or only slightly sunken into blade tissue;-2n-= 148 (Andrews & Windham 1993). Moist areas of canyons (rocky slopes, ledges, crevices), at 1500-2500 m; Boot Springs in Chisos Mts. of Brewster Co. (e.g.,-C.H. Mueller s.n., 1932, BRIT, GH, NY, TEX-LL;-Warnock 1095, BRIT, SRSC, TEX-LL;-O.E. Sperry 1095, TAES), Davis Mts. of Jeff Davis Co. (e.g.,-Palmer 32196, TEX-LL, US) and Chinati Mts., Presidio Co. (M.L. Butterwick & E.J. Lott, 3897, GH, MEXU, TEX-LL-holotype, Wendt 1980); AZ and TX; also n Mexico (Coahuila, Chihuahua, and Sonora). Sporulating summer-fall. [Polypodium riograndense-(T. Wendt) Mickel,-Polypodium thyssanolepis-A. Braun ex Klotzsch var.-riograndense-T. Wendt] This species in the past was considered a variety of-P. thyssanolepis-(e.g., Wendt 1980); however, that species, which is widespread in Mexico, has densely scaly petioles and leaves, the blade scales nearly spherical, mostly areolate venation, and the basal leaf segments opposite or nearly so (Andrews & Windham 1993). Because of its rareness and limited distribution in the state, we consider this species to be of conservation concern in TX