Dryopteris clintoniana (D. C. Eat.) Dowell

Dryopteris clintoniana is a North American endemic and an allohexaploid derived from D . cristata and D . goldiana . Dryopteris clintoniana hybridizes with six species. Hybrids can be identified by the fairly narrow blades and elongate-deltate proximal pinnae.

Leaves dimorphic, 45--100 × 12--20 cm; fertile leaves dying back in winter; sterile leaves 1--several, smaller, green through winter. Petiole 1/4--1/3 length of leaf, scaly at least at base; scales scattered, tan, sometimes with dark brown center. Blade green, lanceolate, with nearly parallel sides, pinnate-pinnatifid, herbaceous, not glandular. Pinnae of fertile leaves twisted out of plane of blade but not fully perpendicular to it, narrowly elongate-deltate; basal pinnae narrowly elongate-deltate, much reduced; basal pinnules longer than or equal to adjacent pinnules, basal basiscopic pinnule and basal acroscopic pinnule equal; pinnule margins serrate or biserrate, with spiny teeth. Sori midway between midvein and margin of segments. Indusia lacking glands. 2 n = 246.

N.B., Ont., Que.; Conn., Ind., Maine, Mass., Mich., N.H., N.J., N.Y., Ohio, Pa., R.I., Vt.

Swampy woods; 50--600m.

Aspidium cristatum (Linnaeus) Swartz var. clintonianum D. C. Eaton in A. Gray, Manual ed. 5, 665. 1867; Dryopteris cristata (Linnaeus) A. Gray var. clintoniana (D. C. Eaton) L. Underwood

Dryopteris clintoniana, commonly known as Clinton's wood fern, is a fern of hybrid origin native to the northern hemisphere. It is a fertile hexaploid, arising as a species by doubling of its chromosome number from a hybrid between Dryopteris cristata, a tetraploid, and Dryopteris goldieana, a diploid. It is more northern in its range than either parent species.

This fern will be found in wet areas, similar to the habitat of D. cristata.