The Collaborative International Dictionary of English v.0.48:

Onoclea \Onoclea\ prop. n.
   A genus consisting of only species: the sensitive fern; in
   some classifications it is included in the Polypodiaceae.

   Syn: genus Onoclea.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

Onoclea
    n 1: one species: sensitive fern; in some classifications
         included in Polypodiaceae [syn: Onoclea, genus Onoclea]