The Collaborative International Dictionary of English v.0.48:

male fern \male fern\ n.
   A fern of North America and Europe (Dryopteris filix-mas)
   whose rhizomes and stalks yield an oleoresin used to expel
   tapeworms. It is a member of the woodfern genus.
   [WordNet 1.5]

WordNet (r) 3.0 (2006):

Dryopteris filix-mas
    n 1: fern of North America and Europe whose rhizomes and stalks
         yield an oleoresin used to expel tapeworms [syn: male
         fern, Dryopteris filix-mas]