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Psilotophyta
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{{Taxobox
| color = lightgreen
| name = Psilotophyta
| image = Psilotum.jpg
| image_width = 240px
| image_caption = Closeup of ''Psilotum nudum''
| regnum =
Plantae
| divisio = Psilotophyta
| classis = Psilotopsida
| ordo = Psilotales
| subdivision_ranks = Families
| subdivision =
Psilotum Psilotaceae
Tmesipteridaceae
Zosterophyllopsidaâ€
}}
'''Psilotophyta''' (the "whisk ferns"; sometimes known as ''Psilophyta'') is a
division (biology) division (i.e., phylum) of the
Kingdom (biology) 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 (the
Psilophyta of the
Devonian period). 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
fungus fungi called
mycorrhizae.
Three
sporangium 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
antheridium antheridia and
archegonium archegonia.
External links
-
Introduction to the Psilotales
Category:Plants sort21 Psilotophyta
Category: cryptogams
bg:ПÑ?илотовидни
de:Urfarne
fr:Psilophyte
he:פסילופיט×?×™×?
no:Psilotaceae
pl:Psylofity
fi:Haarusanikkaiset
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