The Columbia Encyclopedia, Sixth Edition. 2001-07.
thallophyte
common name for members of the Thallophyta (or Thallobionta), a taxonomic group in some archaic classification systems that comprised algae, fungi, and lichens. The thallophytes were considered lower plants and were grouped together because of they consisted of one cell or a relatively undifferentiated mass of cells called a thallus, instead of having an organized plant body (stem, root, and leaf).
