This section is from the book "An Illustrated Flora Of The Northern United States, Canada And The British Possessions Vol1", by Nathaniel Lord Britton, Addison Brown. Also available from Amazon: An Illustrated Flora of the Northern United States, Canada and the British Possessions. 3 Volume Set..
Medium-sized or large ferns with greenish succulent stipes and 1-3-pinnate or pinnatihd blades; veins free; scales of the rootstock delicate, of thin-walled cells. .Sori usually curved, oblong to linear-oblong, or crossing the vein and recurved, sometimes unequally hippocrepi-form, rarely roundish. Indusia shaped like the sorus, attached as in Asplenium, subentire to fimbriate, rarely vestigial and concealed. [Greek, shieldless, of doubtful application.]
Asplenium thelypteroides Michx. Fl. Bor. Am. 2: 265. 1803.
Rootstock slender, sinuous, creeping. Stipes 8'-16' long, straw-colored, somewhat chaffy below, at least when young; blades lanceolate, oblong-lanceolate, or ovate-oblong, 1°-3° long, 6'-12' wide, acute or acuminate, narrowed to the base, very deeply bipinnatifid; pinnae linear-lanceolate to oblong-lanceolate, sessile, acuminate, deeply pinnatifid into numerous oblong obtuse or subacute lightly serrate-crenate segments; sori crowded, curved or straight, the lower often double; indusium light-colored and shining when young.
Bot. 12: 26. 1806. A. Filix-foemina Roth, Romer's Arch. 21: 106. 1799.
Rootstock creeping or ascending, slender for,the size of the plant. Stipes tufted, 6-12' long, straw-colored, brownish or reddish; blades broadly oblong-ovate to oblong-lanceolate, acuminate, l°-3° long, 2-pinnate; pinnae lanceolate, acuminate, short-stalked or the upper ones sessile, 4'-8' long; pinnules oblong-lanceolate to broadly elliptical, incised or serrate, the lobes or teeth often again toothed, those toward the ends of the pinnae confluent; sori short; indusia straight or curved, sometimes horseshoe-shaped.
Blades bipinnatifid; segments lightly crenate-serrate.
Blades bipinnate; pinnules variously incised or deeply serrate.