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 lowland ferns with leaves of two very dissimilar sorts borne separately upon a creeping rootstock, the sterile ones foliaceous and suberect, withering with frosts, the fertile ones rigidly erect, with pinnules greatly contracted into separate hard rounded berry-like divisions, these (until maturity) completely concealing the included sori, finally dehiscent and persistent throughout the winter. Sori roundish, on elevated receotacles, partially covered by delicate hood-shaped indusia fixed at the base of the receptacles. [Name ancient, not originally applied to this plant.}
A single species, O. sensibilis L.
Onoclea sensibilis L. Sp. PI. 1062. 1753-
Rootstock rather slender, copiously rooting. Fertile leaves 1°-2 1/2° high, persistent over winter, the fertile portion bipinnate, much contracted, the short pinnules rolled up into closed berry-like bodies and forming a narrow close panicle. Sterile leaves 1°-4 1/2° high, the blades broadly triangular, deeply pinnatifid, the rachis winged; pinnae lanceolate-oblong, entire, undulate, or the lower and sometimes the middle ones sinuate-pinnatifid; veins freely anastomosing, forming a somewhat regular series of narrow elongate areoles next the midvein and numerous smaller areoles between this series and the margin.
In moist soil, Newfoundland to Saskatchewan, south to Oklahoma and the Gulf states. Ascends to 3000 ft. in Virginia. Various intermediate forms between the sterile and fertile leaves occur. Sensitive to early frosts. Aug.-Nov.