Osmunda Linnaeus (Osmundaceae)

Royal fern

Etymology Of uncertain derivation: from Latin os, bone + munda, cure, because the root was a remedy for rickets; or perhaps from mundae to clean, as it was used medically to clean bones. Perhaps from Osmunder, the Saxon god of war.
Description Rhizome: erect, massive, forming a trunk, occasionally branching, hairs and old stipe bases woven together with black, fibrous roots.
Frond: deciduous, dimorphic.
Stipe: stipules (flared leaf base), unique to the family/genus, hairy when young, vascular bundles: 1 in a U-shape where the top of the arms continue to curl.
Blade: 1-2-pinnate, rachis grooved, somewhat waxy, shedding water, reddish to light brown hairs.
Pinnae: catadromous, often jointed at the rachis, veins free, forked.
Sori: none, indusium: absent, sporangia: large, globose, tan or black when mature, spores green.
Distinctive Characteristics The winged stipes, the vascular bundle, and the large naked sporangium without sorus or indusium, are all unique characters.
O. regalis
Osmunda regalis.  From Bilder ur Nordens Flora (1901-1905), processing by Dr. Gerhard Keuck.
Osmunda
Osmunda regalis, claytoniana, and cinnamomea, left to right: vascular bundles at base of stipe (bottom) and apex of stipe (top). Unique to genus, indistinguishable at the species level.  Drawing from Ferns of Northeastern United States, Farida A. Wiley, 1936.
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