Acrostichoides is the word that means resembling the Acrostichum, a tropical fern, where the sori completely cover the undersurface.
Rhizome: short-creeping, branching, covered with old stipe bases, scales bicolored, dense, broadly lanceolate to linear.
Frond: 25 cm high by 4 cm wide, evergreen, and persistent after withering the following spring, dimorphic, the sterile fronds much shorter than the fertile ones, blade/stipe ratio: 1:3.
Stipe: brown at base, then straw-colored, then green, scales at base and cylindrical hairs scattered along the upper groove of the stipe and rachis, continuing to the costa, vascular bundles: 2.
Blade: 2-pinnate fertile fronds, the sterile sometimes more, deltate to ovate, herbaceous, bright green, hydathodes sunken beneath the surface.
Pinnae: 5 to 6 pair, lanceolate, 1-2 cm, the fertile ones contracted; margins entire; veins free.
Sori: elongate, submarginal, indusium: false, strongly enrolled, sporangia: yellow, maturity: summer.
Habitat: Noncalcareous cliff crevices, rock outcrops, and talus, often in relatively dry habitats, typically montane .
Distribution: western and northern North America at higher altitudes or latitudes, northern China, Mongolia, Siberia.
Hardy to -40°C, USDA Zone 2, requires a cool summer.
Cryptogramma crispa (Linnaeus) R. Brown ex Hooker subsp. acrostichoides (R. Brown) Hultén
Cryptogramma crispa var. acrostichoides (R. Brown) C. B. Clarke
Illustration by Edgar Paulton, from How to Know the Ferns and Fern Allies, John T. Mickel, © 1979 Wm. C. Brown Co.