4. Dryopteris filix-mas (Linnaeus) Schott, Gen. Fil. plate 67. 1834.
Male fern, dryoptère fougère mâle
Polypodium filix-mas Linnaeus, Sp. Pl. 2: 1090. 1753
Leaves monomorphic, dying back in winter, 28--120 × 10--30 cm. Petiole less than 1/4 length of leaf, scaly at least at base; scales scattered, brown, of 2 distinct kinds, 1 broad, 1 hairlike (only this species has 2 distinct forms of scales without intermediates). Blade green, ovate-lanceolate, pinnate-pinnatifid to 2-pinnate at base, firm but not leathery, not glandular. Pinnae ± in plane of blade, lanceolate; basal pinnae ovate-lanceolate, much reduced, basal pinnules or segments ± same length as adjacent pinnules, basal basiscopic pinnule and basal acroscopic pinnule equal; pinnule margins serrate to lobed. Sori midway between midvein and margin of segments. Indusia lacking glands. 2 n = 164.
Dense woods and talus slopes on limestone (ne North America); open woods among boulders and talus of granite or igneous rock (Rocky Mountains); 200--2500 m; Greenland; Alta., B.C., Nfld., N.S., Ont., Que., Sask.; Ariz., Calif., Colo., Idaho, Mich., Mont., N.Mex., Nev., Okla., Oreg., Tex., Utah, Wash., Wis., Wyo.; Europe; Asia.
The taxonomy of Dryopteris filix-mas is not well understood. In North America, this fern has been considered both an auto- and an allopolyploid and may be composed of at least two closely related taxa. Plants in the northeast and northwest are tetraploid. These differ morphologically and ecologically from a taxon of unknown chromosome number in the southwestern Rocky Mountains. The Rocky Mountain taxon closely resembles the Mexican D . pseudofilix-mas (Fée) Rothmaler. Dryopteris filix-mas also occurs in Europe, and it is known to be an allopolyploid of D . caucasica (A. Braun) Fraser-Jenkins & Corley × oreades Fomin.