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..
Coarse ferns of open or partially shaded situations, the triangular or deltoid-ovate compound blades borne upon stout stipes, these scattered upon a slender freely branched woody rootstock creeping underground. Sori in a continuous marginal line, arising from a transverse vein-like receptacle connecting the ends of the forked free veins. Indusium double, the outer conspicuous, formed by the reflexed membranous margin of the blade; the inner obscure, delicate, borne upon the receptacle. [Greek name for ferns.]
Variously regarded as containing one or several species of the "widest distribution, the several forms closely allied to the following, the generic type. P. caudatum occurs in Florida.
Pteris aquilina L. Sp. PI. 1075. 1753. Pteridium aquilinum Kuhn, in Decken's Reisen III. Bot. Ost.-Afrika II. 1879.
Stipe 1°-3° long, straw-colored or brownish, rigid, without chaff, swollen at the base. Blade 2°-4° long, 1°-3° broad, triangular to deltoid-ovate, usually subternate, the long-stalked basal pinnae and the middle ones 2-pinnate, those above 2-pinnate to lobed or simple; segments oblong to lanceolate, the under surface glabrous or pubescent.
The var. pseudocaudatum Clute, from Massachusetts southward, has long linear pinnules, nearly simple.