Diplazium pycnocarpon (Sprengel) M. Broun

Glade fern

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 -30C, 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.
Asplenium pycnocarpon Sprengel
Athyrium pycnocarpon (Sprengel) Tidestrom
Homalosorus pycnocarpos (Sprengel) Pichi-Sermolli
Diplazium pycnocarpon
Diplazium pycnocarpon. a) sterile and fertile fronds, the latter narrower with narrower pinnae; b) fertile pinna, c) veins forking once.  Illustration by V. Fulford from Ferns and Fern Allies of Canada, William J. Cody and Donald M. Britton, 1989, Agriculture Canada, used with permission.
Diplazium pycnocarpon
Diplazium pycnocarpon. Two peanut-shaped vascular bundles at an acute angle at the stipe base uniting upwards to form an inverted v-shape.  Drawing from Ferns of Northeastern United States, Farida A. Wiley, 1936.
Diplazium pycnocarpon
Diplazium pycnocarpon. Habitat: southern Wisconsin forest, an ice-walled lake plain. This is spring when only the sterile fronds can be found.
 Steve White, U.S. Forest Service
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