References: Lellinger (1985); Whetstone & Atkinson in FNA (1993b).
A family of 3 genera and about 15-35 species.
Osmunda Linnaeus (Royal Fern, Cinnamon Fern, Interrupted Fern)
A genus of about 10 species, tropical and temperate.1. Leaves bipinnate, each pinna fully divided into distinct pinnules, the larger pinnules 3-7 cm long and 0.7-2.0 cm wide; spores borne on modified pinnae in the terminal portion of the leaf blade; veins mostly 2-forked...... O. regalis var. spectabilis 1. Leaves pinnate-pinnatifid, each pinna pinnatifid but not divided into distinct pinnules; spores borne either on separate, modified, fertile leaves, or on modified pinnae in the middle of the leaf blade; veins mostly 1-forked......2
Osmunda cinnamomea Linnaeus var. glandulosa Waters, Glandular Cinnamon Fern. Cp, Mt (VA): acidic seepage swamps, sphagnous seeps; rare (VA Rare List). March-May. This taxon is poorly understood, but appears to be worthy of taxonomic recognition. It is known from scattered locations in e. North America. [= F, K; O. cinnamomea -- FNA, in part (infraspecific taxa not distinguished)]
Osmunda claytoniana Linnaeus var. claytoniana, Interrupted Fern. Mt (NC, SC, VA), Pd (VA), Cp (VA): upland forests, woodlands, and balds, moist to rather dry; common (uncommon in Piedmont, rare in Coastal Plain). March-June. Ranging from Newfoundland west to MN, south to n. GA, TN, and AR; another variety occurs in e. and sc. Asia. [= C, F; O. claytoniana -- RAB, FNA, G, K, S, W, infraspecific taxa not distinguished]
Osmunda regalis Linnaeus var. spectabilis (Willdenow) A. Gray, Royal Fern. Cp, Mt, Pd (NC, SC, VA): bogs, marshes (including tidal), moist forests, floodplains, swamp forests; common. March-June. Ranging from Newfoundland west to Saskatchewan, south to FL, TX, and Mexico; var. regalis is widespread in Eurasia. [= RAB, C, F, FNA, G, K, W; O. regalis -- S, varieties not recognized]
The hybrid Osmunda Hruggii R. Tryon [O. claytoniana var. claytoniana H regalis var. spectabilis] is known from Giles County, VA and one other historic population in CT. It has 2-pinnate sterile leaves, with the pinnules sessile.
Flora of the Carolinas and Virginia, Working Draft of 27 October 1997 -- KEY TO PTERIDOPHYTE GENERA. Alan S. Weakley. The Nature Conservancy, Southeast Regional Office, Southern Conservation Science Department.