Psilotophyta
Psilotophyta , division of vascular plants consisting of only two genera, Psilotum and Tmesipteris, with very few species. These plants are characterized by the lack of roots, and, in one species, leaves are lacking also. The green, photosynthetic stem is well-developed. Like higher plants, e.g., the angiosperms ( Magnoliophyta ), Psilotophyta has specialized conducting, or vascular, tissue (xylem and phloem). Psilotum, with only two species, is widespread in tropical and subtropical areas, whereas Tmesipteris species is restricted to Australia and neighboring islands. The spore-producing structures are produced in clusters in the axil of a leaflike at the end of a short lateral branch. The gametophyte plant, arising from germination of a spore, is small and colorless, and derives its nutrition through a specialized association with a fungus. Sexual structures on the gametophyte produce eggs and sperm. The motile sperm, with numerous flagella, are able to swim through a film of water to the egg. The fertilized egg, or zygote, first absorbs nourishment from the gametophyte, and later becomes photosynthetic and self-sustaining. The life cycle is very much like that of ferns .
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Psilotophyta
Book article from: The Columbia Encyclopedia, Sixth Edition
Psilotophyta , division of vascular plants consisting of only two genera, Psilotum...Like higher plants, e.g., the angiosperms ( Magnoliophyta ), Psilotophyta has specialized conducting, or vascular, tissue (xylem and phloem...
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Rhyniophyta
Book article from: The Columbia Encyclopedia, Sixth Edition
...most important. These plants date from the Silurian and Devonian age. Relatively simple in structure, they resemble the Psilotophyta in many features, such as the lack of clearly developed roots. Like modern higher plants the Rhyniophyta had the specialized...
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plant
Book article from: The Columbia Encyclopedia, Sixth Edition
...land. Three of the divisions of the vascular plants are currently represented by only a very few species. They are the Psilotophyta , with only three living species; the Lycopodiophyta (club mosses); and the Equisetophyta (horsetails). All the plants...
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Seedless Vascular Plants
Book article from: Biology
...spore production in living seedless vascular plants is found in the leafless whisk fern, Psilotum, a member of the phylum Psilotophyta. This sporophyte (2n) plant, really little more than a branching twig, has many sets of three-fused sporangia, which...
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