Etymology From pycnos, close, or dense, + carpos, fruit.

Description Rhizome: short-creeping, 5 mm. diam., stipes 1-2 cm. distant, scales brown or tan, broadly lanceolate.
Frond: 100 cm high by 20 cm wide, deciduous, somewhat dimorphic, fertile fronds taller, erect, sterile arching, blade/stipe ratio: 3:1.
Stipe: reddish-brown at base, green upwards, deeply grooved above, a few scales near the base, vascular bundles: 2, curved or peanut-shaped, at an acute angle, uniting to a v-shape above.
Blade: 1-pinnate, oblong-lanceolate, ± narrowed to base, herbaceous to papery, glabrous.
Pinnae: 20 to 40 pair, linear, 1 cm wide; costae grooved above, continuous from rachis to costae; margins entire to crenate; veins free, forking.
Sori: linear or slightly curved , running from midvein halfway or almost to the margin in a herringbone pattern, indusium: linear, persistent, translucent, sinus, sporangia: black, maturity: late summer.

Culture Habitat: moist woods and slopes in neutral soil . Distribution: eastern North America. Hardy to -30°C, USDA Zone 4.

Distinctive Characteristics Narrow, pinnate blades are distinctive. Diplazium pycnocarpon is often placed in the genus Athyrium. FNA assigns it here, calling the usual criterion -- elongate back-to-back sori -- rare. So rare that no photographic example could be found.

Synonyms
Asplenium pycnocarpon Sprengel
Athyrium pycnocarpon (Sprengel) Tidestrom
Homalosorus pycnocarpos (Sprengel) Pichi-Sermolli