Northern maidenhair, adiante du Canada

Adiantum pedatum forma billingsae Kittredge; A. pedatum forma laciniatum (Hopkins) Weatherby

Stems short-creeping; scales bronzy deep yellow, concolored, margins entire. Leaves lax-arching (rarely pendent), closely spaced, 40--75 cm. Petiole 1--2 mm diam., glabrous, occasionally glaucous. Blade fan-shaped, pseudopedate, 1-pinnate distally, 15--30 × 15--35 cm, glabrous; proximal pinnae 3--9-pinnate; rachis straight, glabrous, occasionally glaucous. Segment stalks 0.5--1.5(--1.7) mm, dark color entering into segment base. Ultimate segments oblong, ca. 3 times as long as broad; basiscopic margin straight; acroscopic margin lobed, lobes separated by narrow incisions 0--0.9(--1.1) mm wide; apex obtuse, divided into shallow, rounded lobes separated by shallow sinuses 0.1--2(--3.7) mm deep, margins of lobes crenulate or crenate-denticulate. Indusia transversely oblong, 1--3 mm, glabrous. Spores mostly 34--40 µm diam. 2 n = 58.

Sporulating summer--fall. Rich, deciduous woodlands, often on humus-covered talus slopes and moist lime soils; 0--700 m; N.B., N.S., Ont., Que.; Ala., Ark., Conn., Del., D.C., Ga., Ill., Ind., Iowa, Kans., Ky., La., Maine, Md., Mass., Mich., Minn., Miss., Mo., Nebr., N.H., N.J., N.Y., N.C., Ohio, Okla., Pa., R.I., S.C., Tenn., Vt., Va., W.Va., Wis.

Once considered a single species across its range in North America and eastern Asia, Adiantum pedatum is considered to be a complex of at least three vicariant species ( A . pedatum and A . aleuticum occur in North America) and a derivative allopolyploid species (C. A. Paris 1991). Adiantum pedatum in the strict sense is restricted to deciduous woodlands in eastern North America.