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..
Graceful ferns of rocky hillsides, woods and ravines, with much divided leaves, the stipes and branches slender or filiform, rigid, polished, usually dark-colored and shining. Sori appearing marginal, borne at the ends of the free forking veins, on the under side of reflexed indusiiform marginal lobes of the pinnules or segments. [Name ancient.]
Blades ovate-lanceolate in outline, with a continuous main rachis.
Blades reniform-orbicular, the two equal divisions with pinnate branches.
Adiantum Capillus-Veneris L. Sp. PI. 1096. 1753-
Rootstock creeping, rather slender, chaffy with light-brown scales. Stipes very slender, black, or nearly so and shining, 3'-12' long; blades ovate-lanceolate in outline, 2-pinnate below, simply pinnate above, membranous, 6'-2° long, 4-12' wide at the base; pinnules and upper pinnae wedge-obovate or rhomboid, rather long-stalked, glabrous, the upper margin rounded and more or less deeply incised, the sterile lobes crenate or dentate-serrate, the fertile ones with lunate or transversely oblong indusia; main and secondary rachises and stalks of the pinnules black or dark brown.
In ravines, Virginia to Florida, west to Missouri, Utah and California. Also in South Dakota. Ascends to 1300 ft. in Kentucky. Also in tropical America, and in the warmer parts of the Old World. June-Aug. True or black maiden's-hair. I.ady's-hair. Dudder-grass.
Adiantum pedatum L. Sp. PI. 1095. 1753.
Rootstock slender, creeping, chaffy, rooting along its whole length. Stipes 9'-18' long, dark chestnut-brown, polished and shining, once forked at the summit; blades reni-form-orbicular in outline, 8'-18' broad, membranous, the pinnae arising from the outer sides of the two equal branches, somewhat pedately arranged, the larger ones 6'-10' long, 1'-2' wide; pinnules oblong, triangular-oblong, or the terminal one fan-shaped, short-stalked, the lower margin entire and slightly curved, the upper margin cleft or lobed, the lobes bearing the linear-oblong, often short sori.
In woods. Nova Scotia and Quebec to Alaska, south to Georgia, Louisiana, Kansas; Rocky Mountains to Utah and California. Ascends to 5000 ft. in Virginia. Also in Asia. July-Sept. Most of the western and northwestern specimens and from the Gaspe region, Quebec, are referable to the var. aleuticum Rupr., characterized by its fewer and more strict pinnae and more deeply cleft pinnules and stouter suberect rootstock.