from
The Collaborative International Dictionary of English v.0.48
Thallophyta \Thal*loph"y*ta\, n. pl. [NL. See {Thallophyte}.]
(Bot.)
A phylum of plants of very diverse habit and structure,
including the algae, fungi, and lichens. The simpler forms,
as many blue-green algae, yeasts, etc., are unicellular and
reproduce vegetatively or by means of asexual spores; in the
higher forms the plant body is a thallus, which may be
filamentous or may consist of plates of cells; it is commonly
undifferentiated into stem, leaves, and roots, and shows no
distinct tissue systems; the fronds of many algae, however,
are modified to serve many of the functions of the
above-named organs. Both asexual and sexual reproduction,
often of a complex type, occur in these forms. The
Thallophyta exist almost exclusively as gametophytes, the
sporophyte being absent or rudimentary. By those who do not
separate the Myxophyta from the Tallophyta as a distinct
phylum the latter is treated as the lowermost group in the
vegetable kingdom.
[Webster 1913 Suppl.]