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{{Taxobox
| color = lightgreen
| name = Moss
| image = Haeckel Muscinae.jpg
| image_width = 240px
| image_caption = "Muscinae" from [[Ernst Haeckel]]'s ''[[Kunstformen der Natur]]'', 1904
| regnum = [[Plant]]ae
| divisio = '''Bryophyta'''
| classis = '''Bryopsida'''
| subdivision_ranks = Subclasses
| subdivision =
*[[Sphagnidae]]
*[[Andreaeidae]]
*[[Tetraphidae]]
*[[Polytrichidae]]
*[[Archidiidae]]
*[[Buxbaumiidae]]
*[[Bryidae]]
}}
'''Mosses''' are small, soft [[plant]]s that are typically 1–10 [[centimetre|cm]] tall, or occasionally more. They commonly grow close together in clumps or mats in damp or shady locations. They do not have flowers or [[seed]]s, and their simple [[leaf|leaves]] cover the thin wiry stems. At certain times mosses produces [[spore]] capsules which may appear as beak-like capsules borne aloft on thin stalks.

== Overview ==
Botanically, mosses are [[bryophyte]]s, or [[non-vascular plant]]s. They can be distinguished from the apparently similar [[Marchantiophyta|liverwort]]s ([[Marchantiophyta]] or Hepaticae) by their multi-cellular [[rhizoid]]s. Other differences are not universal for all mosses and all liverworts, but the presence of clearly differentiated "stem" and "leaves", the lack of deeply lobed or segmented leaves, and the absence of leaves arranged in three ranks, all point to the plant being a moss.

There are approximately 10,000 species of moss classified in the Bryophyta. The [[Division (biology)|division]] ''Bryophyta'' formerly included not only mosses, but also liverworts and [[hornwort]]s. These other two groups of [[bryophyte]]s now are often placed in their own divisions.

In addition to lacking a [[Vascular plants|vascular system]], mosses have a gametophyte-dominant [[biological life cycle|life cycle]], i.e. the plant's cells are [[haploid]] for most of its life cycle. Sporophytes (i.e. the [[diploid]] body) are short-lived and dependent on the gametophyte. This is in contrast to the pattern exhibited by most "higher" plants and by most animals. In [[vascular plant]]s, for example, the haploid generation is represented by the pollen and the ovule, whilst the diploid generation is the familiar flowering plant.

==Life cycle==
Most kinds of [[plant]]s have a double portion of [[chromosome]]s in their cells ([[diploid]], i.e. each chromosome exists with a partner that contains the same genetic information) whilst mosses (and other [[bryophyte]]s) have only a single set of chromosomes ([[haploid]], i.e. each chromosome exists in a unique copy within the cell). There are periods in the moss lifecycle when they do have a full, paired set of chromosomes but this is only during the [[sporophyte]] stage.

[[Image:Moss life Cycle.jpg|thumb|left|300px|Life cycle of a typical moss (''Polytrichum commune'')]]

The life of a moss starts from a haploid [[spore]], which germinates to produce a [[protonema]], which is either a mass of filaments or thalloid (flat and thallus-like). This is a transitory stage in the life of a moss. From the protonema grows the gametophore ("gamete-bearer") that is differentiated into stems and leaves ('microphylls'). From the tips of stems or branches develop the sex organs of the mosses. The female organs are known as archegonia (sing. archegonium) and are protected by a group of modified leaves known as the perichaetum (plural, perichaeta). The archegonia have necks called venters which the male sperm swim down. The male organs are known as antheridia (singular antheridium) and are enclosed by modified leaves called the perigonium (plural, perigonia).

Mosses can be either [[dioicous]] (compare [[dioecious]] in seed plants) or [[monoicous]] (compare [[monoecious]]). In dioicous mosses, both male and female sex organs are borne on different gametophyte plants. In monoicous (also called autoicous) mosses, they are borne on the same plant. In the presence of water, sperm from the antheridia swim to the archegonia and [[fertilisation]] occurs, leading to the production of a diploid sporophyte. The sperm of mosses is biflagellate,
i.e. they have two flagella that aid in propulsion. Without water, fertilisation cannot occur. After fertilisation, the immature sporophyte pushes its way out of the archegonial venter. It takes about a quarter to half a year for the [[sporophyte]] to mature. The sporophyte body comprises a long stalk, called a seta, and a capsule capped by a cap called the [[Operculum (Botany)|operculum]]. The capsule and operculum are in turn sheathed by a haploid calyptra which is the remains of the archegonial venter. The calyptra usually falls off when the capsule is mature. Within the capsule, spore-producing cells undergo [[meiosis]] to form haploid spores, upon which the cycle can start again. The mouth of the capsule is usually ringed by a set of teeth called peristome. This may be absent in some mosses.

In some mosses, green vegetative structures called gemmae are produced on leaves or branches, which can break off and form new plants without the need to go through the cycle of fertilisation. This is a means of [[asexual reproduction]].

==Classification of mosses==
[[Image:Three mosses and a tree.jpg|thumb|right|Two different types of mosses (and a lichen, in the smallest box) surround this tree trunk.]]

Mosses were traditionally grouped with the [[Marchantiophyta|liverwort]]s and [[hornwort]]s in the Division [[Bryophyta]] ([[bryophyte]]s), within which the mosses made up the class Musci. This group, however, is [[paraphyletic]] and now tends to be split up. In such system, the Division Bryophyta refers specifically to mosses. They appear to be the closest living relatives of the [[vascular plant]]s.

The mosses are grouped as a single class, now named Bryopsida, and divided into seven subclasses:
* [[Andreaeidae]]
* [[Sphagnidae]]
* [[Tetraphidae]]
* [[Polytrichidae]]
* [[Buxbaumiidae]]
* [[Bryidae]]
* [[Archidiidae]]

Andreaeidae are distinguished by the biseriate (two rows of cells) rhizoids, multiseriate (many rows of cells) protonema, and sporangium that splits along longitudinal lines. Most mosses have capsules that open at the top.

The Sphagnidae, the peat-mosses, comprise the single genus ''[[Sphagnum]]''. These large mosses form extensive acidic bogs in peat swamps. The leaves of ''Sphagnum'' have large dead cells alternating with living photosynthetic cells. The dead cells help to store water. Aside from this character, the unique branching, thallose (flat and expanded) protonema, and explosively rupturing sporangium place it apart from other mosses.

The Tetraphidae are unique (as their name implies) in having only four large peristome teeth surrounding the opening of the capsule.

Polytrichidae have leaves with lamellae, which are flaps on the leaves that look like the fins on a heat sink. These help it retain moisture. They differ from other mosses in other details of their development and anatomy too, and can also become larger than most other mosses, with e.g. ''[[Polytrichum commune]]'' forming cushions up to 40 cm high. The tallest land moss, a member of the Polytrichidae is supposed to be ''Dawsonia superba'', a native to [[New Zealand]] and [[Australia]].

The Buxbaumiidae are called 'bug mosses' because they usually have a very small and reduced gametophore and the whole plant is mostly the sporophyte capsule. The shape reminds one of a bug, which is the reason for its common name.

The Bryidae are the most diverse group; over 95% of moss species belong to this subclass.

The Archidiidae are distinguished by their extremely large spores and the way the sporangium develops.

==Habitat==
[[Image:Mokh.jpg|thumb|A moss-covered tree]]
[[Image:Moss in growth rings.jpg|thumb|Moss growing in the shelter of the growth rings of a stump]]
[[Image:Moss_closeup.jpg|thumb|A closeup of moss on a rock]]
[[Image:Mech plonnik mlode sporofity.jpg|thumb|Young sporophyte of the common hair cap moss (''Polytrichum commune'')]]

Mosses are found chiefly in areas of low light and dampness. Mosses are common in wooded areas and at the edges of streams. Mosses are also found in cracks between paving stones in damp city streets. Some types have adapted to urban conditions and are found only in cities. A few species are wholly aquatic, such as ''Fontinalis antipyretica'', and others such as ''Sphagnum'' inhabit bogs, marshes and very slow-moving waterways. Such aquatic or semi-aquatic mosses can greatly exceed the normal range of lengths seen in terestial mosses. Individual plants 20–30 cm or more long are common in ''Sphagnum'' species for example.

Wherever they occur, mosses require moisture to survive because of the small size and thinness of tissues, lack of cuticle (waxy covering to prevent water loss), and the need for liquid water to complete fertilisation. Some mosses can survive [[desiccation]], returning to life within a few hours of rehydration.

In northern latitudes, the north side of trees and rocks will generally have more moss on average than other sides. This is assumed to be because of the lack of sufficient water for reproduction on the sun-facing side of trees. South of the equator the reverse is true. In deep forests where sunlight does not penetrate, mosses grow equally well on all sides of the tree trunk.

==Cultivation==
Moss is considered a weed in grass lawns, but is deliberately encouraged to grow under aesthetic principles exemplified by [[Japanese garden]]ing. In old temple gardens, moss can carpet a
forest scene. Moss is thought to add a sense of calm, age, and stillness to a garden scene.
Rules of cultivation are not widely established. Moss collections are quite often begun using samples transplanted from the wild in a water-retaining bag. However, specific species of moss can be extremely difficult to maintain away from their natural sites with their unique combinations of light, humidity, shelter from wind, etc.

Growing moss from spores is even less controlled. Moss spores fall in a constant rain on exposed surfaces; those surfaces which are hospitable to a certain species of moss will typically be colonised by that moss within a few years of exposure to wind and rain. Materials which are porous and moisture retentive, such as [[brick]], [[wood]], and certain coarse concrete mixtures are hospitable to moss. Surfaces can also be prepared with acidic substances, including [[buttermilk]], [[yogurt]], [[urine]], and gently puréed mixtures of moss samples, water and [[ericaceous]] [[compost]].

=== Inhibiting moss growth ===
Moss growth can be inhibited by a number of methods:
* Decreasing availability of [[water]] through [[drainage]] or direct application changes.
* Increasing direct sunlight.
* Increasing number and resources available for competitive plants like [[grass]]es.
* Raising the soil [[pH]] with the application of [[Lime (mineral)|lime]].
Heavy traffic or manually disturbing the moss bed with a rake will also inhibit moss growth.

The application of products containing [[ferrous sulfate]] or [[ferrous ammonium sulfate]] will kill moss, these ingredients are typically in commercial moss control products and [[fertilizer]]s. [[Sulfur]] and [[Iron]] are [[essential nutrients]] for some competing plants like grasses. Killing moss will not prevent regrowth unless conditions favorable to their growth are changed.<ref>{{cite web
| last = Steve Whitcher, Master Gardener
| first =
| authorlink =
| coauthors =
| title = Moss Control in Lawns
| work = Gardening in Western Washington
| publisher = Washington State University
| date = 1996
| url = http://gardening.wsu.edu/library/lawn003/lawn003.htm
| format = Web
| doi =
| accessdate = February 10, 2007 }}</ref>

== Mossery ==
A passing fad for moss-collecting in the late 19th century led to the establishment of mosseries in many British and American gardens. The mossery is typically constructed out of slatted wood, with a flat roof, open to the north side (maintaining shade). Samples of moss were installed in the cracks between wood slats. The whole mossery would then be regularly moistened to maintain growth.

== Commercial use==
There is a substantial market in mosses gathered from the wild. The uses for intact moss are principally in the [[Flower|florist]] trade and for home decoration. Decaying moss in the genus ''Sphagnum'' is also the major component of [[peat]], which is "mined" for use as a [[fuel]], as a [[horticulture|horticultural]] soil additive, and in smoking [[malt]] in the production of [[Scotch whisky]]. There are growing concerns in parts of the world where this trade is growing, that significant environmental damage may be caused by commercial peat harvesting. In [[World War II]], ''Sphagnum'' mosses were used as first-aid dressings on soldiers' wounds, as these mosses are highly absorbent and have mild antibacterial properties. Some early people used it as a diaper due to its high absorbency.

In rural [[United Kingdom|UK]], ''Fontinalis antipyretica'' was traditionally used to extinguish fires as it could be found in substantial quantities in slow-moving rivers and the moss retained large volumes of water which helped extinguish the flames. This historical use is reflected in its [[binomial nomenclature|specific]] [[Latin]]/[[Greek language|Greek]] name, the approximate meaning of which is "against fire".

In Finland, peat mosses have been used to make bread during [[famines]].

== See also ==
{{commonscat|Bryophyta}}
* [[Embryophyte]]
* [[Bryophyte]]
* [[Lichen]]

==References==
<references/>

== External links ==
* [http://www.hcs.ohio-state.edu/hcs300/liver2.htm Information, diagrams and photos]
* [http://149.152.32.5/Plant_Biology/moss.html Moss description]
* [http://rbg-web2.rbge.org.uk/bbs/Resources/Fletcher.pdf Moss grower's handbook- 2.39MB, PDF file]
* [http://www.britishbryologicalsociety.org.uk/ The British Bryological Society]
* [http://www.pflanzenliebe.de/innen/innen_moose/innen_moose.html Picture Gallery of Mosses]

[[Category:Bryophyta]]

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