Athyrium alpestre (Hoppe) Clairv.

Alpine lady fern

Etymology Alpestris translates as "growing in the mountains" from alpes, Alps + estris, from.
Description Rhizome: short-creeping, forming massive clumps.
Frond: 80 cm high by 20 cm wide, deciduous, monomorphic, blade/stipe ratio: 2:1 to 3:1.
Stipe: straw-colored or red-brown distally, (7--)10--30 cm, base dark red-brown to black with 2 rows of teeth, swollen, densely scaly at base, sparsely scaly upwards; scales broadly lanceolate to linear, to 1 cm long, pale brown or brown, vascular bundles: 2, lunate, uniting to a U-shape above.
Blade: 2-pinnate pinnatifid, narrowly oblong to ovate-oblong, slightly narrowed downwards, herbaceous, yellow-green to bright green, rachis , costae, and costules with small, pale brown scales.
Pinnae: 8 to 10 pair, lanceolate, 6--10 cm long, pointed at the apex, sessile; pinnules ovate-oblong, acute at apex, 1--2 cm long, 5--8 mm broad, deeply pinnatifid; costae grooved above, continuous from rachis to costae to costules; margins distinctly serrate, teeth sometimes folding over to protect the sori; veins free, forking, usually reaching the margins.
Sori: round to elliptic; in the drawing above it is reniform, medial between the costule and margin, indusium: missing or nearly so, though some forms have one early on, sporangia: black.
Culture Habitat: wet talus slopes, rocky hillsides, alpine meadows. Distribution: high elevations or high latitudes of the Northern Hemisphere. Hardy to -30°C, USDA Zone 4, cool climate required.
Distinctive Characteristics generally looking like a smaller A. filix-femina with the distinguishing characteristics of the sorus shape, and the veins reaching the margin here, not in the lady fern.
Synonyms
Aspidium alpestre Hoppe
Pseudathyrium alpestre (Hoppe) Newman
Athyrium distentifolium Tausch ex Opiz
Athyrium alpestre subsp. americanum (Butters) Lellinger
Athyrium alpestre var. gaspense Fernald
Athyrium americanum (Butters) Maxon
Athyrium distentifolium Tausch ex Opiz subsp. americanum (Butters) Hultén
Athyrium distentifolium var. americanum (Butters) Cronquist
Athyrium alpestre
Athyrium alpestre (A. distentifolium). right: pinnule base with sori, frond and habit.  Illustration from Scandinavian Ferns by Benjamin Ĝllgaard and Kirsten Tind, Rhodos, 1993.
Notes
Compare to A. distentifolium which some observers regard as synonymous, others cite as coarser, shorter, easier to grow, and, the clincher, its indusia are sometimes visible! Not, however, in the cases shown or linked.
Athyrium alpestre
Athyrium alpestre. a) frond 2-pinnate-pinnatifid, pinnae slightly diminished at the base; b) fertile pinnule, naked, round sori, (unique here in the genus) with relexed margin partly protecting the sorus.  Illustration by V. Fulford from Ferns and Fern Allies of Canada, William J. Cody and Donald M. Britton, 1989, İ Agriculture Canada, used with permission.
Athyrium alpestre
Athyrium alpestre. Left to right: pinna base with naked sori, emerging fronds, stipe and rachis scales.  Illustration from Scandinavian Ferns by Benjamin Ĝllgaard and Kirsten Tind, Rhodos, 1993.
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