Woodsia obtusa (Spreng.) Torrey, blunt–leaf cliff fern. Perennial herb, appearing fall–deciduous, rhizomatous, fibrous–leaved, with several leaves arising close to each other from rhizome, in range to 30 cm tall; shoot in range with each leaf each arising directly from rhizome, leaves monomorphic, aboveground with numerous short glandular hairs, in range not viscid; rhizome (not observed).
Leaves (fronds) alternate, odd–2–pinnately compound–lobed having primary leaflets (pinnae) paired and opposite to above midblade widely spaced along rachis changing to alternate upper pinnae close and overlapping, petiolate, without stipules; petiole cylindric at base by channeled from below midpoint, 90+ × 2 mm, with scattered glandular hairs especially above midpetiole, having acuminate–lanceolate to narrowly triangular papery brown scale 3—4 × 1 mm especially at base to below midpoint; blade of 12+ lateral pinnae on each side rachis, ± triangular in outline, in range to 200 × 60 mm, the longest pinnae near base, the terminal pinnae pinnately–1–lobed with sinuses only halfway to midvein; rachis channeled, moderately glandular–pubescent, with pinnae arising on upper side by channel; petiolule of lower pinnae short and pinnae sessile above midblade; pinnae narrowly ovate to triangular, in range 5—30 × 3—5 mm decreasing upward, on the lowermost pinnae the lower secondary pinnae (pinnules) paired with pairs separated and spaced along channeled, lower rachilla but closer and overlapping above midpinna, the pinnules of the large pinnae with sinuses nearly to midvein and other pinnules alternating and overlapping, pinnules sessile and ± ovate, to 6 × 3.5 mm, crenate and with obtuse to acute teeth on margins and obtuse to rounded at tip, pinnately veined with midvein somewhat sunken on upper surface and raised on lower surface, glandular hairs evenly distributed on both surfaces.
Sori on lower surface on lobes between midvein and tips of pinnules, roughly round in outline, mostly 0.6—0.8 mm across, mostly not touching adjacent sori, with < 20 sporangia; indusium shallowly lobed and incomplete around edge of each sorus, ≤ peripheral sporangia, whitish, minutely glandular–ciliate on lobe margins.
Sporangia 0.2—0.25 mm across, reddish brown, ca. 40–spored.
A. C. Gibson