Alaska sword fern

Nephrodium setigerum C. Presl, Reliq. Haenk. 1: 37. 1825; P. braunii (Spenner) Fée subsp. alaskense (Maxon) Calder & R. L. Taylor; P. braunii var. alaskense (Maxon) Hultén

Stems erect. Leaves arching, 4--10 dm; bulblets absent. Petiole 1/8--1/5 length of leaf, densely scaly; scales light brown, gradually diminishing in size distally. Blade lanceolate, deeply 1-pinnate-pinnatifid to 2-pinnate, base narrowed. Pinnae lanceolate, not overlapping, in 1 plane, 4--8 cm, base oblique, margins incised to costa on middle pinnae, serrulate-spiny with teeth spreading-ascending, apex acute-apiculate with subapical and apical teeth same size; microscales filiform, sparse abaxially, confined to costa adaxially. Indusia erose-ciliate. Spores brown. 2 n = 246.

Forest floor in lowland coastal forests; 0--250 m; B.C.; Alaska.

Polystichum setigerum is disjunct on Attu Island at the western tip of the Aleutian Archipelago. It is presumed to be of hybrid origin, the result of a cross between P . munitum and P . braunii (D. H. Wagner 1979). This hybrid has been produced experimentally (A. Sleep and T. Reichstein 1967) and is reported from British Columbia (see discussion under P . braunii ).