Densa means crowded, or thickly packed.
Rhizome: short-creeping, scales brown to black or often bicolored with dark central stripe.
Frond: 25 cm high , evergreen, somewhat dimorphic, fertile fronds with longer stipes and narrower segments, blade/stipe ratio: 1:3.
Stipe: dark reddish brown, with single groove, glabrous, vascular bundles: 1.
Blade: 3-pinnate at base, or more, triangular, leathery , glabrous.
Pinnae: 5 to 7 pair, composed of very narrow segments; pinnules pointed tips; segments linear, 3-8 mm, midrib prominent below; margins entire; veins obscure, free.
Sori: sporangia, submarginal, continuous along length of segments except at apex, indusium: false, inrolled margin, broad, thin, dry, sporangia: dark brown.
Habitat: crevices, rocky outcrops, associated with serpentine, sometimes in chaparral.
Distribution: western North America, British Columbia, western Montana south to Califormia, disjunct in Quebec.
Hardy to -30°C, USDA Zone 4, but given the distribution, the source is likely important.
The long, narrow segments, the very long stipe, and the broad, thin indusium are distinctive.
Onychium densum Brackenridge
Cheilanthes siliquosa Maxon
Pellaea densa (Brackenridge) Hooker