Fragilis means brittle, easily broken, refering to the stipes.
Rhizome: short-creeping, covered with old stipe bases, scales tan to light brown, lanceolate.
Frond: 40 cm high by 6 cm wide, deciduous, monomorphic, blade/stipe ratio: 1:1 or somewhat more.
Stipe: stipes --3 to 8-- clustered at stem apex, grooved, dark at base, straw-colored to green above, sparsely scaly, vascular bundles: 2, round or oblong, merging at stipe apex in the drawing shown below, but not merging in Ferns of Northeastern United States.
Blade: 2-pinnate-pinnatifid, ovate-lanceolate, herbaceous, glabrous.
Pinnae: 8 to 15 pair, subopposite, anadromous, lanceolate, widest just below the middle, perpendicular to the rachis, ± opposite; costae grooves above continuous from rachis to costae; margins serrate to sharply dentate; veins free, simple or forked, ending usually at teeth, forking several times in the pinnule.
Sori: round, in 1 row between midrib and margin, indusium: ovate to lanceolate, forming a hood over the sorus, but shriveling with maturity, beneath sorus on midrib side, sporangia: brown to black, maturity: midsummer to mid fall.
Dimensionality: lowest pinnae pairs bending forward, down, nearly perpendicular to the plane of the frond.
Habitat: calcareous cliff faces, also damp rocks and walls and on thin soil over rock, avoiding the most acidic rocks.
Distribution: temperate Northern and Southern Hemispheres, tropical montane in South America.
Hardy to -40°C, USDA Zone 2.
Polypodium fragile Linnaeus
Cystopteris dickieana Sim