thallophyte

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Any of a group of organisms, including the algae, fungi, and lichens, that show no differentiation into stem, root, or leaf and were formerly regarded as constituting a subkingdom of the plant kingdom.

from The Century Dictionary.

• noun A plant of the subkingdom Thallophyta; one of the lower cryptogams.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Bot.) A plant belonging to the Thallophyta.
• noun (Bot.) Same as Thallogen.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun botany Any of a large number of plants that consist of a thallus only, with no flower, leaves etc.

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

• noun any of a group of cryptogamic organisms consisting principally of a thallus and thus showing no differentiation into stem and root and leaf