Psilotophyta
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| Psilotophyta | ||||||||
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 Closeup of Psilotum nudum | ||||||||
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Psilotophyta (the "whisk ferns"; also sometimes as Psilophyta) is a division (i.e., phylum) of the Kingdom Plantae. This division contains only two genera, Psilotum, a small shrubby plant of the dry tropics, and Tmesipteris, an epiphyte found in Australia, New Zealand, and New Caledonia. There has long been controversy about the relationships of the Psilotophyta, with some claiming that they are ferns (Pteridophyta), and others maintaining that they are descendants of the first vascular plants. Recent evidence from DNA suggests a closer affinity to the ferns.
All Psilotophyta share a few characteristics. Psilotophyta are vascular plants. They lack leaves, instead having small outgrowths called enations. The enations are not considered true leaves because there is only a vascular bundle just underneath them, but not inside, as in leaves. Psilotophyta also do not have true roots. They are anchored by rhizoids. Absorption is aided by symbiotic fungi called mycorrhizae.
Three sporangia are united into a synangium, which is considered to be a very reduced series of branches. There is a thick tapetum to nourish the developing spores, as is typical of eusporangiate plants. The gametophyte looks like a small piece of subterranean stem, but produces antheridia and archegonia.
External links
- Introduction to the Psilotales (http://www.ucmp.berkeley.edu/plants/pterophyta/psilotales.html)de:Urfarne