9. Dryopteris cristata (Linnaeus) A. Gray, Manual. 631. 1848.
Crested wood fern, dryoptère à crêtes
Polypodium cristatum Linnaeus, Sp. Pl. 2: 1090. 1753
Leaves dimorphic, 35--70 × 8--12 cm; fertile leaves dying back in winter; sterile leaves several, small, green through winter, forming "rosette." Petiole 1/4--1/3 length of leaf, scaly at least at base; scales scattered, tan. Blade green, narrowly lanceolate or with parallel sides, pinnate-pinnatifid, not glandular. Pinnae of fertile leaves twisted out of plane of blade and perpendicular to it, deltate; basal pinnae deltate, somewhat reduced, basal pinnules longer than adjacent pinnules, basal basiscopic pinnule and basal acroscopic pinnule equal; pinnule margins distantly serrate, with spiny teeth. Sori midway between midvein and margin of segments. Indusia lacking glands. 2 n = 164.
Swamps, swampy woods, or open shrubby wetlands; 0--1200 m; Alta., B.C., Man., N.B., Nfld., N.S., Ont., P.E.I., Que., Sask.; Ala., Conn., Del., Ill., Ind., Iowa, Maine, Md., Mass., Mich., Minn., Mont., Nebr., N.H., N.J., N.Y., N.C., N.Dak., Ohio, Pa., R.I., Tenn., Vt., Va., W.Va., Wis.; Europe.
Dryopteris cristata is believed to be an allotetraploid derived from D . ludoviciana and an unknown diploid called " D . semicristata " by W. H. Wagner Jr. (1971). This ancestral taxon could have been either North American or Eurasian and may have become extinct during the last glaciation (T. J. Carlson and W. H. Wagner Jr. 1982). Dryopteris cristata hybridizes with five species; these hybrids can be identified by the narrow blades and deltate proximal pinnae.