Obtusa means blunt. The lobes of the indusium are blunt, as are the pinnules.
Rhizome: creeping to erect, scales brown, uniform and others with a dark central stripe.
Frond: 40 cm high by 8 cm wide, evergreen sterile fronds, fertile fronds dying back, monomorphic superficially, but the sterile fronds decline and remain green through winter, blade/stipe ratio: 2:1.
Stipe: persistent bases of unequal lengths, light brown or straw-colored when mature, occasionally darker at very base, scales tan, vascular bundles: 2, oblong, at an acute angle, at stipe base, merging above to a u-shape; the illustration below is not entirely in accord.
Blade: 2-pinnate-pinnatifid at base, rhombic, tapering to both ends, truncated at base, herbaceous, gray-green, glands on both surfaces, rachis, costa with glandular hairs and scattered, often hairlike scales.
Pinnae: 8 to 15 pair, lowest somewhat reduced, sessile or nearly so, pairs further apart the closer to the base; pinnules opposite, 3-8 pairs before degenerating into a pinnatifid pinna tip; costae grooved above, grooves continuous from rachis to costae; margins dentate or lobed; veins free, simple or forked, ending before the margin, vein tips usually enlarged to form whitish hydathodes visible above.
Sori: round, in 1 row between midrib and margin, indusium: four lobes encircling sorus, persistent, translucent, basal, surrounding, sporangia: brown then black, maturity: early to midsummer.
Dimensionality: pinnae held nearly horizontally.
Habitat: rock ledges and slopes.
Distribution: eastern North America.
Hardy to -35°C, USDA Zone 3.
In addition to the genus characteristics, cf.,note the lack of a jointed stipe (a jumble of old stipe bases of various lengths), in summer the diagnostic indusium (see Britton & Brown), in winter the evergreen sterile fronds
Polypodium obtusum Sprengel
Aspidium obtusum Sw.
Cystopteris obtusa Presl
Woodsia perriniana (Sprengel) Hooker & Greville