thallophyta

Century Dictionary and Cyclopedia

1. A subkingdom or group of the vegetable kingdom, embracing the Myxomycetes, Diatomaceæ, Schizophyta, Algæ, and Fungi—the lower cryptogams, as they are still most frequently called. They are plants in which the vegetative body usually consists of a thallus, which shows no differentiation into stem, leaf, and root, or if there is such differentiation it is but rudimentary. In regard to complexity of structure, they set out from the simplest forms which show no outward distinction of parts, and ascend through numberless transitions to more and more complex forms of cell and tissue, but even in the higher forms they are never differentiated into the sharply separated systems of tissue that characterize the higher plants. They never have either true vessels or woody tissue. In regard to the modes of reproduction, they are in as great variety as are the grades of structural complexity, ranging from the forms which are propagated by simple fission to forms that have the sexes as clearly differentiated and almost as perfect and complex as are to be found in the higher plants. Compare Bryophyta, Pteridophyta, Spermophyta, and Cormophyta.

GNU Webster's 1913

1. n. (Bot.) A phylum of plants of very diverse habit and structure, including the algæ, fungi, and lichens. The simpler forms, as many blue-green algæ, 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 algæ, 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.

WordNet 3.0

1. n. used only in former classifications: comprising what is now considered a heterogeneous assemblage of flowerless and seedless organisms: algae; bacteria; fungi; lichens.