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SporePlants213-page10 - states We shall discuss Structure...

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Spore-Dispersing Vascular Plants - 10 Pteridophyta Psilotales (The Whisk Ferns) The Psilotales contains two living genera and records of many fossils dating back about 350-400 million years. Historically they were thought to have been the most primitive of vascular plants; their morphology is similar to the oldest fossil vascular plants. However, DNA evidence has shown that Psilotophytes are evolutionarily advanced but degenerate fern relatives. The two living Genera are: Psilotum Tmesipteris Both genera are found in tropical to subtropical habitats. Psilotum is reasonably abundant in moist areas of Hawaii and is also found in some of the southern US
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Unformatted text preview: states. We shall discuss . Structure As is true of all vascular plants the sporophyte generation of the Psilophytes is predominant. Vascular tissue however, is found just in stems. Psilotum lacks true vascular roots or true vascular leaves. sporophytes have dichotomously branched, vascular aerial stems, which arise from underground vascular rhizomes. Rhizoids, found on the rhizomes, associate with mycorrhizae for absorption of water and nutrients. Enations, small scalelike structures spiral up the stem, and are often thought of as miniature “leaves”....
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