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FNA | Family List | FNA Vol. 2 | Dryopteridaceae | Dryopteris

11. Dryopteris intermedia (Muhlenberg ex Willdenow) A. Gray, Manual. 630. 1848.

Evergreen wood fern, fancy fern, dryoptère spinuleuse

Aspidium intermedium Muhlenberg ex Willdenow, Sp. Pl. 5(1): 262. 1810; Dryopteris austriaca (Jacquin) Woynar var. intermedia (Muhlenberg ex Willdenow) C. V. Morton; D. spinulosa (O. F. Mueller) Watt var. intermedia (Muhlenberg ex Willdenow) L. Underwood

Leaves monomorphic, green through winter, 32--90 × 10--20 cm. Petiole 1/3 length of leaf, scaly at least at base; scales scattered, tan. Blade green, ovate, 3-pinnate-pinnatifid, herbaceous, glandular. Pinnae ± in plane of blade, lanceolate-oblong; basal pinnae lanceolate, not reduced, basal pinnules longer than adjacent pinnules, basal basiscopic pinnule longer than basal acroscopic pinnule; pinnule margins serrate, teeth spiny. Sori midway between midvein and margin of segments. Indusia with minute glandular hairs. 2 n = 82.

Moist rocky woods, especially hemlock hardwoods, ravines, and edges of swamps; 0--2000 m; N.B., Nfld., N.S., Ont., P.E.I., Que.; Ala., Conn., Del., Ga., Ill., Ind., Iowa, Ky., Maine, Md., Mass., Mich., Minn., Mo., N.H., N.J., N.Y., N.C., Ohio, Pa., R.I., Tenn., Vt., Va., W.Va., Wis.

A related taxon, Dryopteris intermedia subsp. maderensis (J. Milde ex Alston) Fraser-Jenkins, occurs on eastern Atlantic islands.

Dryopteris intermedia and the other taxa in the " D . spinulosa complex" have long confounded taxonomists. Dryopteris intermedia is diploid and is one of the parents of the allotetraploids D . carthusiana and D . campyloptera . Dryopteris intermedia hybridizes with eight species. All hybrids are easily detected by the distinctive glandular hairs on the indusia and, usually, on the costae and costules.


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