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

Distribution

V2 500-distribution-map.gif

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

Discussion

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 </i>var.<i> americanum than to var. distentifolium, and they need further study.

References

None.

Lower Taxa

No lower taxa listed.