From The Collaborative International Dictionary of English v.0.48 [gcide]:
Osmund \Os"mund\, n. (Bot.)
A fern of the genus Osmunda, or flowering fern. The most
remarkable species is the osmund royal, or royal fern
(Osmunda regalis), which grows in wet or boggy places, and
has large bipinnate fronds, often with a panicle of capsules
at the top. The rootstock contains much starch, and has been
used in stiffening linen.
[1913 Webster]
From WordNet (r) 3.0 (2006) [wn]:
osmund
n 1: any fern of the genus Osmunda: large ferns with creeping
rhizomes; naked sporangia are on modified fronds that
resemble flower clusters [syn: flowering fern, osmund]