Psilotophyta


Closeup of the branches of a whisk fern, Psilotum nudum

Psilotophyta (the so-called "whisk ferns"; also sometimes as Psilophyta) is a division (ie. 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 (Pterophyta), 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 all 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 don't have true roots. They are anchored by rhizoids. Absorption is aided by 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.


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