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Psilotum is a genus of fern-like vascular plants.It is one of two genera in the family Psilotaceae commonly known as whisk ferns, the other being Tmesipteris.Plants in these two genera were once thought to be descended from the earliest surviving vascular plants, but more recent phylogenies place them as basal ferns, as a sister group to Ophioglossales.
Pteridophyte life cycle Just as with bryophytes and spermatophytes (seed plants), the life cycle of pteridophytes involves alternation of generations . This means that a diploid generation (the sporophyte, which produces spores) is followed by a haploid generation (the gametophyte or prothallus , which produces gametes ).
The family contains two genera, Psilotum and Tmesipteris. The first genus, Psilotum , consists of small shrubby plants of the dry tropics commonly known as "whisk ferns". The other genus, Tmesipteris , is an epiphyte found in Australia , New Zealand , and New Caledonia .
Tmesipteris, the hanging fork ferns, is a genus of ferns, one of two genera in the family Psilotaceae, order Psilotales (the other being Psilotum). Tmesipteris is restricted to certain lands in the Southern Pacific, notably Australia, New Zealand and New Caledonia.
The life cycle of a typical fern proceeds as follows: A diploid sporophyte phase produces haploid spores by meiosis (a process of cell division which reduces the number of chromosomes by a half). A spore grows into a free-living haploid gametophyte by mitosis (a process of cell division which maintains the number of chromosomes).
Psilotum nudum, the whisk fern, [3] is a fernlike plant. Like the other species in the order Psilotales, it lacks roots. [4]Its name, Psilotum nudum, means "bare naked" in Latin, because it lacks (or seems to lack) most of the organs of typical vascular plants, as a result of evolutionary reduction.
Leafless, dichotomously branching fossils bearing spines and possessing vascular tissue from the Devonian of Gaspé Peninsula, Canada, were thought by Dawson in 1859 to resemble the modern whiskfern, Psilotum. Accordingly, he named his new genus Psilophyton, the type species being P. princeps.
Equisetum (/ ˌ ɛ k w ɪ ˈ s iː t əm /; horsetail) is the only living genus in Equisetaceae, a family of vascular plants that reproduce by spores rather than seeds. [2]Equisetum is a "living fossil", the only living genus of the entire subclass Equisetidae, which for over 100 million years was much more diverse and dominated the understorey of late Paleozoic forests.