lichenes

from The Century Dictionary.

• A division of cellular, mostly thalloid, cryptogamic plants, formerly regarded as constituting a distinct class, but now, in accordance with the theory of Schwendener and others, considered to be genuine fungi of the divisions Ascomycetes and Basidiomycetes. They exhibit a remarkable parasitism.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun comprising the lichens which grow symbiotically with algae; sometimes treated as an independent group more or less coordinate with algae and fungi