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..
Royal Fern Family. Large ferns with creeping or suberect rootstocks. Stipes winged at the base, the blades 1-2-pinnate or tripinnatifid, with free mostly forked veins extending to the margins. Sporanges naked, large, globose, mostly stalked, borne on modified contracted pinnae and nearly covering them or (in Todea and Leptopteris. Old World genera) in clusters (sori) on the lower surface of the pinnules or segments, opening in 2 valves by a longitudinal slit; ring wanting or mere traces of one near the apex.
Three living genera, Osmunda and the two mentioned.