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Psilotaceae
Psilotaceae is a family of ferns (class Polypodiopsida) consisting of two genera, ''Psilotum'' and ''Tmesipteris'' with about a dozen species. It is the only family in the order Psilotales. Description Once thought to be descendants of early vascular plants (the Psilophyta of the Devonian period), Psilotaceae have been shown by molecular phylogenetics to be ferns (Polypodiopsida), and a sister group of the Ophioglossaceae. 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. All members of Psilotaceae are vascular plants without any true roots. Rather, the plants are anchored by an underground system of rhizomes. The small, stem-like gametophytes of Psilotaceae are located in this rhizome system, and they aid in a plant's nutrient absorption through ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Psilotaceae
Psilotaceae is a family of ferns (class Polypodiopsida) consisting of two genera, ''Psilotum'' and ''Tmesipteris'' with about a dozen species. It is the only family in the order Psilotales. Description Once thought to be descendants of early vascular plants (the Psilophyta of the Devonian period), Psilotaceae have been shown by molecular phylogenetics to be ferns (Polypodiopsida), and a sister group of the Ophioglossaceae. 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. All members of Psilotaceae are vascular plants without any true roots. Rather, the plants are anchored by an underground system of rhizomes. The small, stem-like gametophytes of Psilotaceae are located in this rhizome system, and they aid in a plant's nutrient absorption through ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Psilotum
''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. They lack true roots and leaves are very reduced, the stems being the organs containing photosynthetic and conducting tissue. There are only two species in ''Psilotum'' and a hybrid between the two. They differ from those in ''Tmesipteris'' in having stems with many branches and a synangium with three lobes rather than two. Description and life cycle Whisk ferns in the genus ''Psilotum'' lack true roots but are anchored by creeping rhizomes. The stems have many branches with paired enations, which look like small leaves but have no vascular tissue. Above these enations there are synangia formed by the fusion of three sp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polypodiopsida
A fern (Polypodiopsida or Polypodiophyta ) is a member of a group of vascular plants (plants with xylem and phloem) that reproduce via spores and have neither seeds nor flowers. The polypodiophytes include all living pteridophytes except the lycopods, and differ from mosses and other bryophytes by being vascular, i.e., having specialized tissues that conduct water and nutrients and in having life cycles in which the branched sporophyte is the dominant phase. Ferns have complex leaves called megaphylls, that are more complex than the microphylls of clubmosses. Most ferns are leptosporangiate ferns. They produce coiled fiddleheads that uncoil and expand into fronds. The group includes about 10,560 known extant species. Ferns are defined here in the broad sense, being all of the Polypodiopsida, comprising both the leptosporangiate (Polypodiidae) and eusporangiate ferns, the latter group including horsetails, whisk ferns, marattioid ferns, and ophioglossoid ferns. Ferns first ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tmesipteris
''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. In New Zealand this hanging epiphyte is common in the warm temperate rain forests of both main islands, where it can normally be found as short spiky dark-green fronds (10–15 cm long), often with lighter bag-like sporangia at the bases of some of its "leaves". The plant possesses no true leaves; what appear to be leaves Phylloclade, are flattened stems. The fronds emerge directly from the fibrous root-mats which clad the trunks of mature tree ferns such as ''Dicksonia'' and ''Cyathea''. ''Tmesipteris'' is from the Greek language, meaning a "cut fern", referring to the truncated leaf tips. Species Species include: *''Tmesipteris elongata'' P.A.Dang - from Australia (Victoria and Tasmania) and New Ze ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fern
A fern (Polypodiopsida or Polypodiophyta ) is a member of a group of vascular plants (plants with xylem and phloem) that reproduce via spores and have neither seeds nor flowers. The polypodiophytes include all living pteridophytes except the lycopods, and differ from mosses and other bryophytes by being vascular, i.e., having specialized tissues that conduct water and nutrients and in having life cycles in which the branched sporophyte is the dominant phase. Ferns have complex leaves called megaphylls, that are more complex than the microphylls of clubmosses. Most ferns are leptosporangiate ferns. They produce coiled fiddleheads that uncoil and expand into fronds. The group includes about 10,560 known extant species. Ferns are defined here in the broad sense, being all of the Polypodiopsida, comprising both the leptosporangiate (Polypodiidae) and eusporangiate ferns, the latter group including horsetails, whisk ferns, marattioid ferns, and ophioglossoid ferns. Ferns first ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Eusporangiate Fern
Eusporangiate ferns are vascular spore plants, whose sporangia arise from several epidermal cells and not from a single cell as in leptosporangiate ferns. Typically these ferns have reduced root systems and sporangia that produce large amounts of spores (up to 7000 spores per sporangium in '' Christensenia'') There are four extant eusporangiate fern families, distributed among three classes. Each family is assigned to its own order. *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 **Order Equisetales, family Equisetaceae – Horsetails (1 genus, about 15 species) *Class Marattiopsida **Order Marattiales, family Marattiaceae – Marattoid ferns (6 genera, about 500 species) The following diagram shows a likely phylogenic placement of eusporangiate fern classes within the vascular plants. Cladistics While it ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Psilotum Nudum
''Psilotum nudum'', the whisk fern, is a fernlike plant. Like the other species in the order Psilotales, it lacks roots. 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. (Note that leaves are not actually absent, but greatly reduced.) Development The embryo has only two parts, a distal shoot apex and a proximal foot. The shoot apex produces a rhizome without roots, possibly because ''P. nudum'' and relatives are often epiphytes. The rhizome in turn will eventually produce greatly reduced leaves instead of roots. These processes are heavily influenced by auxin concentrations. Distribution ''P. nudum'' is found in tropical Africa, Central America, tropical and subtropical North America, South America, tropical Asia, Australia, Hawaii, southern Japan, Lord Howe Island, New Zealand, with a few isolated populations in SW Europe ("Los Alcornocales", Sp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Psilophytopsida
Psilophytopsida is a now obsolete class containing one order, Psilophytales, which was previously used to classify a number of extinct plants which are now placed elsewhere. The class was established in 1917, under the name Psilophyta, with only three genera (''Rhynia'', ''Horneophyton'' and ''Psilophyton'') for a group of fossil plants from the Upper Silurian and Devonian periods which lack true roots and leaves, but have a vascular system within a branching cylindrical stem. The living Psilotaceae, the whisk-ferns, were sometimes added to the class, which was then usually called Psilopsida. This classification is no longer in use. The class should not be confused with the current use of the name Psilotopsida, which refers to a class of living ferns, containing only Psilotaceae (whisk-ferns) and Ophioglossaceae (moon-worts and adder's-tongue ferns). Description The class was created in 1917 by Kidston and Lang for fossils found in the Rhynie Chert Bed. Three genera were i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gametophyte
A gametophyte () is one of the two alternation of generations, alternating multicellular organism, multicellular phases in the life cycles of plants and algae. It is a haploid multicellular organism that develops from a haploid spore that has one set of chromosomes. The gametophyte is the Sexual reproduction of plants, sexual phase in the life cycle of plants and algae. It develops sex organs that produce gametes, haploid sex cells that participate in fertilization to form a diploid zygote which has a double set of chromosomes. Cell division of the zygote results in a new diploid multicellular organism, the second stage in the life cycle known as the sporophyte. The sporophyte can produce haploid spores by meiosis that on germination produce a new generation of gametophytes. Algae In some multicellular green algae (''Ulva lactuca'' is one example), red algae and brown algae, sporophytes and gametophytes may be externally indistinguishable (isomorphic). In ''Ulva (genus), Ulv ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Devonian
The Devonian ( ) is a geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, where rocks from this period were first studied. The first significant adaptive radiation of life on dry land occurred during the Devonian. Free-sporing vascular plants began to spread across dry land, forming extensive forests which covered the continents. By the middle of the Devonian, several groups of plants had evolved leaves and true roots, and by the end of the period the first seed-bearing plants appeared. The arthropod groups of myriapods, arachnids and hexapods also became well-established early in this period, after starting their expansion to land at least from the Ordovician period. Fish reached substantial diversity during this time, leading the Devonian to often be dubbed the Age of Fishes. The placoderms began dominating ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phylloclade
Phylloclades and cladodes are flattened, photosynthetic shoots, which are usually considered to be modified branches. The two terms are used either differently or interchangeably by different authors. ''Phyllocladus'', a genus of conifer, is named after these structures. Phylloclades/cladodes have been identified in fossils dating from as early as the Permian. Definition and morphology The term "phylloclade" is from the New Latin ''phyllocladium'', itself derived from Greek ''phyllo'', leaf, and ''klados'', branch. Definitions of the terms "phylloclade" and "cladode" vary. All agree that they are flattened structures that are photosynthetic and resemble leaf-like branches. In one definition, phylloclades are a subset of cladodes, namely those that greatly resemble or perform the function of leaves, as in Butcher's broom (''Ruscus aculeatus'') as well as ''Phyllanthus'' and some ''Asparagus'' species. By an alternative definition, cladodes are distinguished by their limited gr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ophioglossidae
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). The subclass contains two orders, Psilotales and Ophioglossales, whose relationship was only confirmed by molecular phylogenetic studies. Taxonomy Smith et al. (2006) carried out the first higher-level pteridophyte classification published in the molecular phylogenetic era, and considered the ferns (monilophytes), with four classes. They placed the whisk ferns and related taxa in the class Psilotopsida, with two orders. Mark W. Chase and James L. Reveal (2009) classified them as two separate subclasses, Psilotidae and Ophioglossidae, corresponding to those orders within a much broader grouping, the class Equisetopsida ''sensu lato''. Christenhusz ''et al.'', 2011, included both the Ophioglossal ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
