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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.
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.
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).
Psilotaceae is a family of ferns (class Polypodiopsida) consisting of two genera, Psilotum and Tmesipteris with about a dozen species. [1] It is the only family in the order Psilotales . [ 2 ]
Ophioglossidae is one of the four subclasses of Polypodiopsida (ferns). This subclass consists of the ferns commonly known as whisk ferns, grape ferns, adder's-tongues and moonworts. It is equivalent to the class Psilotopsida in previous treatments, including Smith et al. (2006). [2]
The term "fern ally" included under Pteridophyta generally refers to vascular spore-bearing plants that are not ferns, including lycopods, horsetails, whisk ferns and water ferns (Marsileaceae, Salviniaceae and Ceratopteris). This is not a natural grouping but rather a convenient term for non-fern, and is also discouraged, as is eusporangiate ...
There are four extant eusporangiate fern families, distributed among three classes. Each family is assigned to its own order. [1] [2] Class Psilotopsida. Order Psilotales, family Psilotaceae – Whisk ferns (2 genera, about 17 species) Order Ophioglossales, family Ophioglossaceae – Adder's-tongues (5 genera, about 80 species) Class Equisetopsida
Traditionally, whisk ferns and horsetails were historically treated as distinct from 'true' ferns. [51] Living whisk ferns and horsetails do not have the large leaves (megaphylls) which would be expected of euphyllophytes. This has probably resulted from reduction, as evidenced by early fossil horsetails, in which the leaves are broad with ...