Athyrium distentifolium var. americanum

(Butters) Boivin
Naturaliste Canad. 93: 272. 1966..
Common names: American alpine lady fern athyrie alpestre sous-espèce américaine
Synonyms: Athyrium alpestre var. americanum Butters Athyrium americanum (Butters) Maxon Athyrium americanum subsp. americanum (Butters) Lellinger Athyrium alpestre var. gaspense Fernald Athyrium distentifolium subsp. americanum (Butters) Hultén
Treatment appears in FNA Volume 2.

Stems ascending or short-creeping. Petiole straw-colored or red-brown distally, (7–)10–30 cm, base dark red-brown to black with 2 rows of teeth, swollen; scales at base brown to dark brown, lanceolate or broadly lanceolate, 13 × 3(–5) mm. Blade narrowly elliptic or lanceolate, 2–3-pinnate-pinnatifid, 15–55(–65) × 3–25 cm, moderately narrowed proximally, broadest below middle, apex acuminate. Pinnae short-stalked, narrowly deltate to deltate-oblong, apex acute. Pinnules deeply pinnatifid, segments oblong, crenulate. Rachis, costae, and costules with small, pale brown scales. Veins pinnate. Sori round to elliptic; indusia absent or very minute, scalelike. 2n = 80.

Habitat: Wet talus slopes, rocky hillsides, alpine meadows
Elevation: 600–3100 m


V2 500-distribution-map.gif

Greenland, Alta., B.C., Nfld. and Labr. (Nfld.), Que., Yukon, Alaska, Calif., Colo., Idaho, Mont., Nev., Oreg., Utah, Wash., Wyo.


Athyrium distentifolium var. americanum differs from var. distentifolium of Europe in its more finely dissected leaves with crenulate pinnule-segments, relatively broader pinnae with abruptly larger basal pinnules, and much more rudimentary indusia, if any. Japanese plants are more similar to var. americanum than to var. distentifolium, and they need further study.

Selected References


Lower Taxa


Masahiro Kato +
(Butters) Boivin +
American alpine lady fern +  and athyrie alpestre sous-espèce américaine +
Greenland +, Alta. +, B.C. +, Nfld. and Labr. (Nfld.) +, Que. +, Yukon +, Alaska +, Calif. +, Colo. +, Idaho +, Mont. +, Nev. +, Oreg. +, Utah +, Wash. +  and Wyo. +
600–3100 m +
Wet talus slopes, rocky hillsides, alpine meadows +
Naturaliste Canad. +
Athyrium alpestre var. americanum +, Athyrium americanum +, Athyrium americanum subsp. americanum +, Athyrium alpestre var. gaspense +  and Athyrium distentifolium subsp. americanum +
Athyrium distentifolium var. americanum +
Athyrium distentifolium +
variety +