The Collaborative International Dictionary of English v.0.48:

Charales \Charales\ n.
   a small order of macroscopic fresh and brackish water algae
   with a distinct axis; the stoneworts.

   Syn: order Charales.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

Charales
    n 1: small order of macroscopic fresh and brackish water algae
         with a distinct axis: stoneworts [syn: Charales, order
         Charales]