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The Marchantiophyta () are a division of non-vascular
land plant The Embryophyta (), or land plants, are the most familiar group of green plant Plants are predominantly photosynthetic Photosynthesis is a process used by plants and other organisms to Energy transformation, convert light energy into ...

land plant
s commonly referred to as hepatics or liverworts. Like
mosses Mosses are small, non-vascular flower A flower, sometimes known as a bloom or blossom Cherry blossoms in Paris in full bloom. In botany, blossoms are the flowers of stone fruit fruit tree, trees (genus ''Prunus'') and of some other plant ...

mosses
and
hornworts Hornworts are a group of bryophytes (a group of non-vascular plants) constituting the division Anthocerotophyta (). The common name refers to the elongated horn-like structure, which is the sporophyte. As in mosses and liverworts, the flattened, ...
, they have a
gametophyte A gametophyte () is one of the two alternating multicellular phases in the life cycles of plant Plants are predominantly photosynthetic Photosynthesis is a process used by plants and other organisms to Energy transformation, convert ...
-dominant life cycle, in which cells of the plant carry only a single set of genetic information. It is estimated that there are about 9000 species of liverworts. Some of the more familiar species grow as a flattened leafless
thallus Thallus (plural: thalli), from Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through th ...
, but most species are leafy with a form very much like a flattened
moss Mosses are small, non-vascular flower A flower, sometimes known as a bloom or blossom Cherry blossoms in Paris in full bloom. In botany, blossoms are the flowers of stone fruit fruit tree, trees (genus ''Prunus'') and of some other plant ...

moss
. Leafy species can be distinguished from the apparently similar mosses on the basis of a number of features, including their single-celled
rhizoid Rhizoids are protuberances that extend from the lower epidermal cells of bryophyte Bryophytes are an informal group consisting of three divisions Division or divider may refer to: Mathematics *Division (mathematics) Division is one of th ...
s. Leafy liverworts also differ from most (but not all) mosses in that their leaves never have a costa (present in many mosses) and may bear marginal
cilia The cilium (; the plural is cilia) is an organelle In cell biology Cell biology (also cellular biology or cytology) is a branch of biology Biology is the natural science that studies life and living organisms, including their anatomy, ...
(very rare in mosses). Other differences are not universal for all mosses and liverworts, but the occurrence of leaves arranged in three ranks, the presence of deep lobes or segmented leaves, or a lack of clearly differentiated stem and leaves all point to the plant being a liverwort. Liverworts are typically small, usually from 2–20 mm wide with individual plants less than 10 cm long, and are therefore often overlooked. However, certain species may cover large patches of ground, rocks, trees or any other reasonably firm substrate on which they occur. They are distributed globally in almost every available habitat, most often in humid locations although there are desert and Arctic species as well. Some species can be a nuisance in shady greenhouses or a weed in gardens.


Physical characteristics


Description

Most liverworts are small, measuring from wide with individual plants less than long, so they are often overlooked. The most familiar liverworts consist of a prostrate, flattened, ribbon-like or branching structure called a
thallus Thallus (plural: thalli), from Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through th ...
(plant body); these liverworts are termed ''thallose liverworts''. However, most liverworts produce flattened stems with overlapping scales or leaves in two or more ranks, the middle rank is often conspicuously different from the outer ranks; these are called '' leafy liverworts'' or ''scale liverworts''.Schofield, W. B. ''Introduction to Bryology'', pp. 135–140. (New York: Macmillan, 1985). . (''See the
gallery Gallery may refer to: Arts, entertainment, and media Music Groups * Gallery (band), an American soft rock band of the 1970s Albums * ''Gallery'' (Elaiza album), 2014 album * ''Gallery'' (Great White album), a 1999 compilation album * ''Galler ...
below for examples.'') Liverworts can most reliably be distinguished from the apparently similar
moss Mosses are small, non-vascular flower A flower, sometimes known as a bloom or blossom Cherry blossoms in Paris in full bloom. In botany, blossoms are the flowers of stone fruit fruit tree, trees (genus ''Prunus'') and of some other plant ...

moss
es by their single-celled
rhizoid Rhizoids are protuberances that extend from the lower epidermal cells of bryophyte Bryophytes are an informal group consisting of three divisions Division or divider may refer to: Mathematics *Division (mathematics) Division is one of th ...
s. Other differences are not universal for all mosses and all liverworts; but the lack of clearly differentiated stem and leaves in thallose species, or in leafy species the presence of deeply lobed or segmented leaves and the presence of leaves arranged in three ranks, all point to the plant being a liverwort. Unlike any other embryophytes, most liverworts contain unique membrane-bound oil bodies containing isoprenoids in at least some of their cells, lipid droplets in the cytoplasm of all other plants being unenclosed.Harold C. Bold, C. J. Alexopoulos, and T. Delevoryas. ''Morphology of Plants and Fungi'', 5th ed., p. 189. (New York: Harper-Collins, 1987). . The overall physical similarity of some mosses and leafy liverworts means that confirmation of the identification of some groups can be performed with certainty only with the aid of
microscopy Microscopy is the technical field of using microscopes to view objects and areas of objects that cannot be seen with the naked eye (objects that are not within the resolution range of the normal eye). There are three well-known branches of micr ...

microscopy
or an experienced bryologist . Liverworts, like other bryophytes, have a
gametophyte A gametophyte () is one of the two alternating multicellular phases in the life cycles of plant Plants are predominantly photosynthetic Photosynthesis is a process used by plants and other organisms to Energy transformation, convert ...
-dominant life cycle, with the
sporophyte A sporophyte () is the diploid Ploidy () is the number of complete sets of chromosomes in a cell (biology), cell, and hence the number of possible alleles for Autosome, autosomal and Pseudoautosomal region, pseudoautosomal genes. Sets of chr ...
dependent on the gametophyte. Cells in a typical liverwort plant each contain only a single set of genetic information, so the plant's cells are
haploid Ploidy () is the number of complete sets of chromosome A chromosome is a long DNA molecule with part or all of the genetic material of an organism. Most eukaryotic chromosomes include packaging proteins called histones which, aided by ...
for the majority of its life cycle. This contrasts sharply with the pattern exhibited by nearly all animals and by vascular plants. In the more familiar
seed plant A seed is an embryonic ''Embryonic'' is the twelfth studio album by experimental rock band the Flaming Lips released on October 13, 2009, on Warner Bros. Records, Warner Bros. The band's first double album, it was released to generally positi ...
s, the haploid generation is represented only by the tiny
pollen Pollen is a powdery substance consisting of pollen grains which are microsporophytes of seed plants The spermatophytes (; ), also known as phanerogams (taxon Phanerogamae) or phaenogams (taxon Phaenogamae), comprise those plant Plant ...

pollen
and the
ovule In seed plant A seed is an embryonic ''Embryonic'' is the twelfth studio album by experimental rock band the Flaming Lips released on October 13, 2009, on Warner Bros. Records, Warner Bros. The band's first double album, it was released ...

ovule
, while the
diploid Ploidy () is the number of complete sets of chromosomes in a cell (biology), cell, and hence the number of possible alleles for Autosome, autosomal and Pseudoautosomal region, pseudoautosomal genes. Sets of chromosomes refer to the number of mate ...
generation is the familiar tree or other plant. Another unusual feature of the liverwort life cycle is that sporophytes (i.e. the
diploid Ploidy () is the number of complete sets of chromosomes in a cell (biology), cell, and hence the number of possible alleles for Autosome, autosomal and Pseudoautosomal region, pseudoautosomal genes. Sets of chromosomes refer to the number of mate ...
body) are very short-lived, withering away not long after releasing spores. In mosses, the sporophyte is more persistent and in hornworts, the sporophyte disperses spores over an extended period.


Life cycle

The life of a liverwort starts from the germination of a haploid
spore In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mecha ...
to produce a
protonema A protonema (plural: protonemata) is a thread-like chain of cells that forms the earliest stage of development of the gametophyte (the haploid Ploidy () is the number of complete sets of chromosome A chromosome is a long DNA molecule wi ...

protonema
, which is either a mass of thread-like filaments or else a flattened thallus. The protonema is a transitory stage in the life of a liverwort, from which will grow the mature gametophore ("
gamete A gamete ( /ˈɡæmiːt/; from Ancient Greek Ancient Greek includes the forms of the Greek language Greek ( el, label=Modern Greek Modern Greek (, , or , ''Kiní Neoellinikí Glóssa''), generally referred to by speakers simply ...
-bearer") plant that produces the sex organs. The male organs are known as
antheridia An antheridium is a haploid Ploidy () is the number of complete sets of chromosome A chromosome is a long DNA molecule with part or all of the genetic material of an organism. Most eukaryotic chromosomes include packaging proteins cal ...

antheridia
(''singular:'' antheridium) and produce the sperm cells. Clusters of antheridia are enclosed by a protective layer of cells called the perigonium (''plural:'' perigonia). As in other land plants, the female organs are known as
archegonia An archegonium (pl: archegonia), from the ancient Greek Ancient Greek includes the forms of the Greek language Greek ( el, label=Modern Greek Modern Greek (, , or , ''Kiní Neoellinikí Glóssa''), generally referred to by speak ...

archegonia
(''singular:'' archegonium) and are protected by the thin surrounding perichaetum (''plural:'' perichaeta). Each archegonium has a slender hollow tube, the "neck", down which the sperm swim to reach the egg cell. Liverwort species may be either
dioicous Dioicy () is a sexual system A sexual system is a pattern of sex allocationSex allocation is the allocation of resources to male versus female reproduction in sexual species.Charnov EL. (1982). ''The Theory of Sex Allocation''. Princeton Univers ...
or
monoicous Monoicy () is a sexual system in haploid Ploidy () is the number of complete sets of chromosome A chromosome is a long DNA molecule with part or all of the genetic material of an organism. Most eukaryotic chromosomes include packag ...
. In dioicous liverworts, female and male sex organs are borne on different and separate gametophyte plants. In monoicous liverworts, the two kinds of reproductive structures are borne on different branches of the same plant. In either case, the sperm must move from the antheridia where they are produced to the archegonium where the eggs are held. The
sperm Sperm is the male reproductive Cell (biology), cell, or gamete, in anisogamous forms of sexual reproduction (forms in which there is a larger, female reproductive cell and a smaller, male one). Animals produce motile sperm with a tail known as ...

sperm
of liverworts is ''biflagellate'', i.e. they have two tail-like flagellae that enable them to swim short distances,Campbell, Douglas H. ''The Structure and Development of Mosses and Ferns'', pp. 73–74. (London: The Macmillan Co., 1918)
/ref> provided that at least a thin film of water is present. Their journey may be assisted by the splashing of raindrops. In 2008, Japanese researchers discovered that some liverworts are able to fire sperm-containing water up to 15 cm in the air, enabling them to fertilize female plants growing more than a metre from the nearest male. When sperm reach the archegonia,
fertilisation Fertilisation or fertilization (see spelling differences Despite the various English dialects Dialect The term dialect (from Latin , , from the Ancient Greek word , , "discourse", from , , "through" and , , "I speak") is used in ...

fertilisation
occurs, leading to the production of a diploid sporophyte. After fertilisation, the immature
sporophyte A sporophyte () is the diploid Ploidy () is the number of complete sets of chromosomes in a cell (biology), cell, and hence the number of possible alleles for Autosome, autosomal and Pseudoautosomal region, pseudoautosomal genes. Sets of chr ...
within the archegonium develops three distinct regions: (1) a foot, which both anchors the sporophyte in place and receives nutrients from its "mother" plant, (2) a spherical or ellipsoidal capsule, inside which the spores will be produced for dispersing to new locations, and (3) a seta (stalk) which lies between the other two regions and connects them. The sporophyte lacks an
apical meristem The meristem is a type of tissue Tissue may refer to: Biology * Tissue (biology), an ensemble of similar cells that together carry out a specific function * ''Triphosa haesitata'', a species of geometer moth found in North America * ''Triphosa du ...
, an
auxin Auxins (plural of auxin ) are a class of plant hormone Plant hormones (or phytohormones) are signal molecule In biology, cell signaling (cell signalling in British English), or cell-cell communication, governs the basic activities of cell (bio ...

auxin
-sensitive point of divergence with other land plants some time in the
Late Silurian The Silurian ( ) is a period (geology), geologic period and system spanning 24.6 million years from the end of the Ordovician Period, at million years ago (annum, Mya), to the beginning of the Devonian Period, Mya. The Silurian is the shortes ...
/
Early Devonian The Devonian ( ) is a period (geology), geologic period and system of the Paleozoic, 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, ...
. When the sporophyte has developed all three regions, the seta elongates, pushing its way out of the archegonium and rupturing it. While the foot remains anchored within the parent plant, the capsule is forced out by the seta and is extended away from the plant and into the air. Within the capsule, cells divide to produce both
elater An elater is a cell (or structure attached to a cell) that is hygroscopic Hygroscopy is the phenomenon of attracting and holding water molecules via either absorption (chemistry), absorption or adsorption from the surrounding Natural environ ...
cells and spore-producing cells. The elaters are spring-like, and will push open the wall of the capsule to scatter themselves when the capsule bursts. The spore-producing cells will undergo
meiosis Meiosis (; , because it is a reductional division) is a special type of of in organisms used to produce the , such as or . It involves two rounds of division that ultimately result in four cells with only one copy of each (). Additionall ...

meiosis
to form haploid
spore In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mecha ...
s to disperse, upon which point the life cycle can start again.


Asexual reproduction

Some liverworts are capable of
asexual reproduction Asexual reproduction is a type of reproduction Reproduction (or procreation or breeding) is the biological process Biological processes are those processes that are vital for an organism In biology, an organism (from Ancient Gree ...
; in bryophytes in general "it would almost be true to say that vegetative reproduction is the rule and not the exception." For example, in ''
Riccia ''Riccia'' is a genus of liverwort The Marchantiophyta are a division of non-vascular land plants commonly referred to as hepatics or liverworts. Like mosses and hornworts, they have a gametophyte A gametophyte () is one of the two al ...
'', when the older parts of the forked thalli die, the younger tips become separate individuals. Some thallose liverworts such as ''
Marchantia polymorpha ''Marchantia polymorpha'', sometimes known as the common liverwort or umbrella liverwort, is a large Marchantiophyta, liverwort with a wide distribution around the world. It is variable in appearance and has several subspecies. It is monoicous, d ...

Marchantia polymorpha
'' and '' Lunularia cruciata'' produce small disc-shaped gemmae in shallow cups. ''Marchantia'' gemmae can be dispersed up to 120 cm by rain splashing into the cups. In '' Metzgeria'', gemmae grow at thallus margins. ''Marchantia polymorpha'' is a common weed in greenhouses, often covering the entire surface of containers; gemma dispersal is the "primary mechanism by which liverwort spreads throughout a nursery or greenhouse."


Ecology

Today, liverworts can be found in many ecosystems across the planet except the sea and excessively dry environments, or those exposed to high levels of direct solar radiation. As with most groups of living plants, they are most common (both in numbers and species) in moist tropical areas. Liverworts are more commonly found in moderate to deep shade, though desert species may tolerate direct sunlight and periods of total desiccation.


Classification


Relationship to other plants

Traditionally, the liverworts were grouped together with other
bryophyte Bryophytes are an informal group consisting of three divisions Division or divider may refer to: Mathematics *Division (mathematics) Division is one of the four basic operations of arithmetic, the ways that numbers are combined to make new n ...

bryophyte
s (
moss Mosses are small, non-vascular flower A flower, sometimes known as a bloom or blossom Cherry blossoms in Paris in full bloom. In botany, blossoms are the flowers of stone fruit fruit tree, trees (genus ''Prunus'') and of some other plant ...

moss
es and
hornwort Hornworts are a group of bryophyte Bryophytes are an informal group consisting of three divisions Division or divider may refer to: Mathematics *Division (mathematics) Division is one of the four basic operations of arithmetic, the ways th ...
s) in the Division Bryophyta, within which the liverworts made up the class Hepaticae (also called Marchantiopsida). Somewhat more recently, the liverworts were given their own division (Marchantiophyta), as bryophytes became considered to be
paraphyletic In taxonomy Taxonomy (general) is the practice and science of classification of things or concepts, including the principles that underlie such classification. The term may also refer to a specific classification scheme. Originally used only ...
. However, the most recent phylogenetic evidence indicates that liverworts are indeed likely part of a monophyletic clade ("Bryophyta ''sensu lato''" or "Bryophyta Schimp.") alongside mosses and hornworts. Hence, it has been suggested that the liverworts should be de-ranked to a class called Marchantiopsida. In addition, there is strong phylogenetic evidence to suggest that liverworts and mosses form a monophyletic subclade named Setaphyta. An important conclusion from these phylogenies is that the ancestral stomata appear to have been lost in the liverwort lineage. Among the earliest
fossil A fossil (from Classical Latin Classical Latin is the form of Latin language Latin (, or , ) is a classical language A classical language is a language A language is a structured system of communication used by humans, inc ...

fossil
s believed to be liverworts are
compression fossil A compression fossil is a fossil preserved in sedimentary rock that has undergone compression (physical), physical compression. While it is uncommon to find animals preserved as good compression fossils, it is very common to find plants preserved ...
s of '' Pallaviciniites'' from the Upper
Devonian The Devonian ( ) is a geologic period and system of the Paleozoic The Paleozoic (or Palaeozoic) Era ( ; from the Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the H ...
of
New York New York most commonly refers to: * New York City, the most populous city in the United States, located in the state of New York * New York (state), a state in the northeastern United States New York may also refer to: Film and television * New ...
. These fossils resemble modern species in the
Metzgeriales Metzgeriales is an Order (biology), order of Marchantiophyta, liverworts. The group is sometimes called the simple thalloid liverworts: "thallus, thalloid" because the members lack structures resembling stems or leaves, and "simple" because thei ...
. Another Devonian fossil called '''' also looks like a liverwort, but its relationship to other plants is still uncertain, so it may not belong to the Marchantiophyta. In 2007, the oldest fossils assignable at that time to the liverworts were announced, ''Metzgeriothallus sharonae'' from the
Givetian The Givetian is one of two faunal stage In chronostratigraphyChronostratigraphy is the branch of stratigraphy that studies the ages of rock stratum, strata in relation to time. The ultimate aim of chronostratigraphy is to arrange the sequence o ...
(Middle
Devonian The Devonian ( ) is a geologic period and system of the Paleozoic The Paleozoic (or Palaeozoic) Era ( ; from the Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the H ...
) of
New York New York most commonly refers to: * New York City, the most populous city in the United States, located in the state of New York * New York (state), a state in the northeastern United States New York may also refer to: Film and television * New ...
, United States. However, in 2010, five different types of fossilized liverwort spores were found in Argentina, dating to the much earlier Middle
Ordovician The Ordovician ( ) is a geologic period The geologic time scale (GTS) is a system of chronological dating that classifies Geology, geological strata (stratigraphy) in time. It is used by geologists, paleontology, paleontologists, and other eart ...

Ordovician
, around 470 million years ago.Walker, Matt. "Fossils of earliest land plants discovered in Argentina

(BBC, Earth News, 2010).


Internal classification

Bryology, Bryologists classify liverworts in the division Marchantiophyta. This divisional name is based on the name of the most universally recognized liverwort genus ''
Marchantia ''Marchantia'' is a genus of Marchantiophyta, liverworts in the Family (biology), family Marchantiaceae and the Order (biology), order Marchantiales. The thallus of ''Marchantia'' shows differentiation into two layers: an upper photosynthetic l ...

Marchantia
''. In addition to this
taxon In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechani ...
-based name, the liverworts are often called Hepaticophyta. This name is derived from their common Latin name as Latin was the language in which botanists published their descriptions of species. This name has led to some confusion, partly because it appears to be a taxon-based name derived from the
genus Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank In biological classification In biology, taxonomy () is the scientific study of naming, defining (Circumscription (taxonomy), circumscribing) and classifying gr ...
''
Hepatica ''Hepatica'' (hepatica, liverleaf, or liverwort) is a genus Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank In biological classification In biology, taxonomy () is the scientific study of naming, defini ...

Hepatica
'' which is actually a
flowering plant Flowering plants include multiple members of the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greec ...

flowering plant
of the buttercup family
Ranunculaceae Ranunculaceae (buttercup or crowfoot family; Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latiu ...
. In addition, the name Hepaticophyta is frequently misspelled in textbooks as Hepatophyta, which only adds to the confusion. Although there is no consensus among bryologists as to the classification of liverworts above family rank, the Marchantiophyta may be subdivided into three classes: * The Jungermanniopsida includes the two
orders Orders is a surname In some cultures, a surname, family name, or last name is the portion of one's personal name 300px, First/given, middle and last/family/surname with John Fitzgerald Kennedy as example. This shows a structure typical f ...
Metzgeriales Metzgeriales is an Order (biology), order of Marchantiophyta, liverworts. The group is sometimes called the simple thalloid liverworts: "thallus, thalloid" because the members lack structures resembling stems or leaves, and "simple" because thei ...
(simple thalloids) and
Jungermanniales Jungermanniales is the largest Order (biology), order of Marchantiophyta, liverworts. They are distinctive among the liverworts for having thin leaf-like flaps on either side of the stem. Most other liverworts are thalloid, with no leaves. Famil ...
(leafy liverworts). * The Marchantiopsida includes the three orders
Marchantiales Marchantiales is an Order (biology), order of thallose Marchantiophyta, liverworts (also known as "complex thalloid liverworts") that includes species like ''Marchantia polymorpha'', a widespread plant often found beside rivers, and ''Lunularia c ...
(complex-thallus liverworts), and Sphaerocarpales (bottle hepatics), as well as the
Blasiales Blasiales is an order (biology), order of Marchantiophyta, liverworts with a single living family (biology), family and two species. The order has traditionally been classified among the Metzgeriales, but molecular cladistics suggests a placement ...
(previously placed among the Metzgeriales). It also includes the problematic genus '' Monoclea'', which is sometimes placed in its own order Monocleales. * A third class, the
Haplomitriopsida Haplomitriopsida is a newly recognized Class (biology), class of Marchantiophyta, liverworts comprising fifteen species in three genus, genera. Recent cladistics, cladistic analyses of cell nucleus, nuclear, mitochondrial, and plastid gene seque ...
is newly recognized as the sister group of the other liverworts; it comprises the genera '' Haplomitrium'', ''
Treubia ''Treubia'' is a genus of Marchantiophyta, liverworts in the Family (biology), family Treubiaceae.Crandall-Stotler, Barbara. & Stotler, Raymond E. (2000). "Morphology and classification of the Marchantiophyta". pages 21–70 ''in'' A. Jonath ...
'', and '' Apotreubia''. An updated classification by Söderström et al. 2016 * Marchantiophyta Stotler & Crandall-Stotler 2000 **
Haplomitriopsida Haplomitriopsida is a newly recognized Class (biology), class of Marchantiophyta, liverworts comprising fifteen species in three genus, genera. Recent cladistics, cladistic analyses of cell nucleus, nuclear, mitochondrial, and plastid gene seque ...
Stotler & Crandall-Stotler 1977 *** Calobryales Hamlin 1972 ***
Treubiales Treubiaceae is a family (biology), family of Marchantiophyta, liverworts in the Order (biology), order Treubiales.Crandall-Stotler, Barbara. & Stotler, Raymond E. "Morphology and classification of the Marchantiophyta". page 63 ''in'' A. Jonathan ...
Schljakov 1972 **
Marchantiopsida Marchantiopsida is one of three classes within the liverwort phylum Marchantiophyta. Phylogeny Based on the work by Villarreal et al. 2015 Taxonomy * Blasiidae He-Nygrén et al. 2006 ** Blasiales Stotl. & Crand.-Stotl. 2000 *** Blasiaceae H.K ...
Cronquist, Takhtajan & Zimmermann 1966 *** Blasiidae He-Nygrén et al. 2006 ****
Blasiales Blasiales is an order (biology), order of Marchantiophyta, liverworts with a single living family (biology), family and two species. The order has traditionally been classified among the Metzgeriales, but molecular cladistics suggests a placement ...
Stotler & Crandall-Stotler 2000 *** Marchantiidae Engler 1893 sensu He-Nygrén et al. 2006 ****
Lunulariales ''Lunularia cruciata'', the crescent-cup liverwort, is a Marchantiophyta, liverwort of the order Marchantiales (until recently included in the Order (biology), order Lunulariales), and the only species in the genus ''Lunularia'' and family L ...
Long 2006 ****
Marchantiales Marchantiales is an Order (biology), order of thallose Marchantiophyta, liverworts (also known as "complex thalloid liverworts") that includes species like ''Marchantia polymorpha'', a widespread plant often found beside rivers, and ''Lunularia c ...
Limpricht 1877 (complex thalloids) **** Neohodgsoniales Long 2006 **** Sphaerocarpales Cavers 1910 (bottle liverworts) **
Jungermanniopsida Jungermanniopsida is the largest of three classes within the division Marchantiophyta (liverworts). Phylogeny Based on the work by Novíkov & Barabaš-Krasni 2015. Taxonomy * Jungermanniidae Engler 1893 ** Jungermanniales von Klinggräff 1858 ...
Stotler & Crandall-Stotler 1977 *** Jungermanniidae Engler 1893 (leafy liverworts) ****
Jungermanniales Jungermanniales is the largest Order (biology), order of Marchantiophyta, liverworts. They are distinctive among the liverworts for having thin leaf-like flaps on either side of the stem. Most other liverworts are thalloid, with no leaves. Famil ...
von Klinggräff 1858 ****
Porellales Porellales is an Order (biology), order of liverworts. Taxonomy * Jubulineae Müller 1909 ** Frullaniaceae Lorch 1914 *** ''Frullania'' Raddi 1818a 'Amphijubula'' Schuster 1970a; ''Schusterella'' Hattori, Sharp & Mizutani 1972; ''Steerea'' Hat ...
Schljakov 1972 **** Ptilidiales Schljakov 1972 *** Metzgeriidae Bartholomew-Began 1990 ****
Metzgeriales Metzgeriales is an Order (biology), order of Marchantiophyta, liverworts. The group is sometimes called the simple thalloid liverworts: "thallus, thalloid" because the members lack structures resembling stems or leaves, and "simple" because thei ...
Chalaud 1930 ****
Pleuroziales ''Pleurozia'' is the only genus of Marchantiophyta, liverworts in the Family (biology), family Pleuroziaceae, which is now classified in its own order Pleuroziales, but was previously included in a broader circumscription of the Jungermanniales. ...
Schljakov 1972 *** Pelliidae He-Nygrén et al. 2006 **** Fossombroniales Schljakov 1972 ****
Pallaviciniales Pallaviciniales is an Order (biology), order of liverworts. Taxonomy * Pallaviciniineae Schuster 1984 ** Hymenophytaceae Schuster 1963 *** ''Hymenophyton'' Dumortier 1835 'Umbraculum (plant), Umbraculum'' Gottsche 1861 non Schumacher 1817 non ...
Frey & Stech 2005 **** Pelliales He-Nygrén et al. 2006 It is estimated that there are about 9000 species of liverworts, at least 85% of which belong to the leafy group. Despite that fact, no liverwort genomes have been sequenced to date and only few genes identified and characterized.


Economic importance

In ancient times, it was believed that liverworts cured diseases of the liver, hence the name. In Old English, the word liverwort literally means ''liver plant''. This probably stemmed from the superficial appearance of some thalloid liverworts which resemble a liver in outline, and led to the common name of the group as ''hepatics'', from the
Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the power of the Roman Republic, it became ...

Latin
word ''hēpaticus'' for "belonging to the liver". An unrelated flowering plant, ''
Hepatica ''Hepatica'' (hepatica, liverleaf, or liverwort) is a genus Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank In biological classification In biology, taxonomy () is the scientific study of naming, defini ...

Hepatica
'', is sometimes also referred to as liverwort because it was once also used in treating diseases of the liver. This archaic relationship of plant form to function was based in the "Doctrine of Signatures".Stern, Kingsley R. ''Introductory Plant Biology'', 5th ed., p. 338. (Dubuque, Iowa: Wm. C. Brown Publishers, 1991) . Liverworts have little direct economic importance today. Their greatest impact is indirect, through the reduction of erosion along streambanks, their collection and retention of water in tropical forests, and the formation of
soil crust Soil crusts are soil Surface-water- gley developed in glacial till, Northern Ireland.">Northern_Ireland.html" ;"title="glacial till, Northern Ireland">glacial till, Northern Ireland. Soil is a mixture of organic matter, minerals, gases, liqu ...
s in deserts and polar regions. However, a few species are used by humans directly. A few species, such as ''
Riccia fluitans ''Riccia fluitans'', whose common name is floating crystalwort, is an aquatic floating plant of the Marchantiophyta, liverwort genus ''Riccia'' which is popular among aquarists as a retreat for young fry and is used in live-bearing tanks. It can b ...
'', are aquatic thallose liverworts sold for use in
aquarium An aquarium (plural: ''aquariums'' or ''aquaria'') is a vivarium Biosphere 2 in Oracle, Arizona A vivarium (Latin, literally for "place of life"; plural: ''vivaria'' or ''vivariums'') is an area, usually enclosed, for keeping and raisi ...

aquarium
s. Their thin, slender branches float on the water's surface and provide habitat for both small invertebrates and the fish that feed on them.


Gallery

A small collection of images showing liverwort structure and diversity: Image:Marchantia.jpg,
''
Marchantia ''Marchantia'' is a genus of Marchantiophyta, liverworts in the Family (biology), family Marchantiaceae and the Order (biology), order Marchantiales. The thallus of ''Marchantia'' shows differentiation into two layers: an upper photosynthetic l ...

Marchantia
polymorpha'', with antheridial and archegonial stalks.
Image:Archegonium.jpg,
The
archegonium An archegonium (pl: archegonia), from the ancient Greek Ancient Greek includes the forms of the Greek language Greek ( el, label=Modern Greek Modern Greek (, , or , ''Kiní Neoellinikí Glóssa''), generally referred to by speak ...

archegonium
of ''Porella''.
Image:Porella SPT.jpg,
A sporophyte of ''Porella'' emerging from its archegonium.
Image:Porella platyphylla.jpg,
'' Porella platyphylla'' clump growing on a tree.
Image:Pellia epiphylla5 ies.jpg,
'' Pellia epiphylla'', growing on moist soil.
Image:Plagiochila aspleniodes0.jpg,
'' Plagiochila asplenioides'', a
leafy liverwort Jungermanniales is the largest Order (biology), order of Marchantiophyta, liverworts. They are distinctive among the liverworts for having thin leaf-like flaps on either side of the stem. Most other liverworts are thalloid, with no leaves. Famili ...
.
Image:RicciaFluitans1.jpg,
''
Riccia fluitans ''Riccia fluitans'', whose common name is floating crystalwort, is an aquatic floating plant of the Marchantiophyta, liverwort genus ''Riccia'' which is popular among aquarists as a retreat for young fry and is used in live-bearing tanks. It can b ...
'', an aquatic thallose liverwort.
Image:Liverwort.jpg,
'' Conocephalum conicum'', a large thallose liverwort.


See also

*
Bryophyte Bryophytes are an informal group consisting of three divisions Division or divider may refer to: Mathematics *Division (mathematics) Division is one of the four basic operations of arithmetic, the ways that numbers are combined to make new n ...

Bryophyte
*
Embryophyte The Embryophyta (), or land plants, are the most familiar group of green plant Plants are predominantly photosynthetic Photosynthesis is a process used by plants and other organisms to Energy transformation, convert light energy into ...

Embryophyte


References


External links

* *
Liverwort structure in pictures

LiToL: Assembling the Liverwort Tree of Life
(note: for 500,000 million years ago read "480 million years ago".)





{{Good article Plant divisions Early Ordovician first appearances Extant Ordovician first appearances