Diplazium sibiricum (Turcz. ex Kunze) Sa. Kurata
Etymology Sibericum is Siberia.
Description Rhizome: long-creeping, 3 mm. diam., stipes distant, scales large, glossy blackish-brown.
Frond: 90 cm high by 40 cm wide, deciduous, yellowing well before frost, somewhat dimorphic, fertile fronds taller, erect, sterile arching, blade/stipe ratio: 1:1 or less.
Stipe: black at base, straw-colored to pale green above, scales lanceolate to broadly lanceolate, to 10 mm long, to 3 mm broad, brown to blackish brown, polished, rather firm, twisted in distal portion, toothed at margin, becoming sparse on the rachis, vascular bundles: 2, lunate.
Blade: 2-pinnate-pinnatifid, but both more and less reported, triangular, abruptly narrowed tip, herbaceous, green above, pale green beneath, glabrous above and on lamina below, but costae and veins with hairs below.
Pinnae: 10 to 15 pair, lanceolate, to 10 cm broad at the base of the lowest ones; pinnules ovate-oblong ; costae grooved above, continuous from rachis to costae; margins crenate to dentate; veins free, forking.
Sori: linear, basal sori paired back-to-back on the same vein, others singular, indusium: linear, falling soon, whitish, margin toothed, sinus, sporangia: black, maturity: midsummer.
Dimensionality: lower pinnae turned down, forward; another source: up, backward.
Culture Habitat: steep, forested river gorges. Distribution: northern Europe, across to Siberia, south to China, Korea, Japan, Vietnam, and eastwards through the Himalayas. Hardy to -25°C, USDA Zone 5.
Distinctive Characteristics long-creeping, modest size, triangular blade, long stipe, 2-pinnate-pinnatifid
Athyrium crenatum (Sommerf.) Rupr.
Aspidium sibiricum Turcz.
Cystopteris crenata Fries
Diplazium sommerfeldtii A.Löve & D.Löve
Diplazium sibiricum
Diplazium sibiricum. from right: stipe scales, pinnule with various sori, close-up of sorus showing fimbriated margin of indusium.  Illustration from Scandinavian Ferns by Benjamin Øllgaard and Kirsten Tind, Rhodos, 1993.
Variation The Flora of Japan mentions a var. glabrum which one presumes is glabrous, but the text reverses the assessment. Elsewhere the species is described as having hairs on the costae. Assume there is a glabrous version somewhere.
Diplazium sibiricum
Diplazium sibiricum.Click through and expand: one can see the grooves of costa continuous with the rachis groove, a generic character.
 Finland: Suomussalmi, Vasonniemi, 5.7.2008, Photo © Harri Arkkio
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