Bryopsida
Encyclopedia
The Bryopsida constitute the largest class
of moss
es, containing 95% of all moss species
. It consists of approximately 11,500 species, common throughout the whole world.
The group is distinguished by having spore capsules
with teeth that are arthrodontous; the teeth are separate from each other and jointed at the base where they attach to the opening of the capsule. These teeth are exposed when the covering operculum
falls off. In other groups of mosses, the capsule is either nematodontous with an attached operculum, or else splits open without operculum or teeth.
) and its pattern of development is very useful both for classifying and for identifying moss families. Most Bryopsida produce a capsule with a lid (the operculum
) which falls off when the spore
s inside are mature and thus ready to be dispersed. The opening thus revealed is called the stoma (meaning "mouth") and is surrounded by one or two peristomes. A peristome
is a ring of triangular "teeth" formed from the remnants of specially thickened cell wall
s. There are usually 16 such teeth in a single peristome, and in the Bryopsida the teeth are separate from each other and able to both fold in to cover the stoma as well as fold back to open the stoma. This articulation of the teeth is termed arthrodontous.
There are two basic arthrodontous peristome types. The first type is termed haplolepidous and consists of a single circle of 16 peristome teeth. This type of peristome is characteristic of subclass Dicranidae
. The second type is the diplolepidous peristome found in subclasses Bryidae
, Funariidae
, and Timmiidae. In this type, there are two rings of peristome teeth—an inner endostome (short for endoperistome) and an exostome. The endostome is a more delicate membrane, and its teeth are aligned between the teeth of the exostome. There are a few mosses in the Bryopsida that have no peristome in their capsules. These mosses still undergo the same cell division patterns in capsule development, but the teeth do not fully develop.
Class (biology)
In biological classification, class is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, order, family, genus, and species, with class fitting between phylum and order...
of moss
Moss
Mosses are small, soft plants that are typically 1–10 cm tall, though some species are much larger. They commonly grow close together in clumps or mats in damp or shady locations. They do not have flowers or seeds, and their simple leaves cover the thin wiry stems...
es, containing 95% of all moss species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
. It consists of approximately 11,500 species, common throughout the whole world.
The group is distinguished by having spore capsules
Sporangium
A sporangium is an enclosure in which spores are formed. It can be composed of a single cell or can be multicellular. All plants, fungi, and many other lineages form sporangia at some point in their life cycle...
with teeth that are arthrodontous; the teeth are separate from each other and jointed at the base where they attach to the opening of the capsule. These teeth are exposed when the covering operculum
Operculum (botany)
An operculum, in botany, is a term generally used to describe a structure within a plant, moss, or fungus acting as a cap, flap, or lid. In plants, it may also be called a bud cap.Examples of structures identified as opercula include:...
falls off. In other groups of mosses, the capsule is either nematodontous with an attached operculum, or else splits open without operculum or teeth.
Capsule structure
Among the Bryopsida, the structure of the capsule (sporangiumSporangium
A sporangium is an enclosure in which spores are formed. It can be composed of a single cell or can be multicellular. All plants, fungi, and many other lineages form sporangia at some point in their life cycle...
) and its pattern of development is very useful both for classifying and for identifying moss families. Most Bryopsida produce a capsule with a lid (the operculum
Operculum (botany)
An operculum, in botany, is a term generally used to describe a structure within a plant, moss, or fungus acting as a cap, flap, or lid. In plants, it may also be called a bud cap.Examples of structures identified as opercula include:...
) which falls off when the spore
Spore
In biology, a spore is a reproductive structure that is adapted for dispersal and surviving for extended periods of time in unfavorable conditions. Spores form part of the life cycles of many bacteria, plants, algae, fungi and some protozoa. According to scientist Dr...
s inside are mature and thus ready to be dispersed. The opening thus revealed is called the stoma (meaning "mouth") and is surrounded by one or two peristomes. A peristome
Peristome
The word peristome is derived from the Greek peri, meaning 'around' or 'about', and stoma, 'mouth'. It is a term used to describe various anatomical features that surround an opening to an organ or structure. The term is used in plants and invertebrate animals, such as in describing the shells of...
is a ring of triangular "teeth" formed from the remnants of specially thickened cell wall
Cell wall
The cell wall is the tough, usually flexible but sometimes fairly rigid layer that surrounds some types of cells. It is located outside the cell membrane and provides these cells with structural support and protection, and also acts as a filtering mechanism. A major function of the cell wall is to...
s. There are usually 16 such teeth in a single peristome, and in the Bryopsida the teeth are separate from each other and able to both fold in to cover the stoma as well as fold back to open the stoma. This articulation of the teeth is termed arthrodontous.
There are two basic arthrodontous peristome types. The first type is termed haplolepidous and consists of a single circle of 16 peristome teeth. This type of peristome is characteristic of subclass Dicranidae
Dicranidae
The Dicranidae are a widespread group of mosses in class Bryopsida, with many species of dry or disturbed areas....
. The second type is the diplolepidous peristome found in subclasses Bryidae
Bryidae
Bryidae is an important subclass of Bryopsida. It is common throughout the whole world. Members have a double peristome with alternating tooth segments.-Classification:The classification of the Bryidae.Superorder: Bryanae...
, Funariidae
Funariidae
The Funariidae are a widespread group of mosses in class Bryopsida. The majority of species belong to the genera Funaria and Physcomitrium ....
, and Timmiidae. In this type, there are two rings of peristome teeth—an inner endostome (short for endoperistome) and an exostome. The endostome is a more delicate membrane, and its teeth are aligned between the teeth of the exostome. There are a few mosses in the Bryopsida that have no peristome in their capsules. These mosses still undergo the same cell division patterns in capsule development, but the teeth do not fully develop.
Classification
In the past, the group Bryopsida included all mosses. Current circumscriptions of the group are more limited.subclass Bryopsida
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| The current composition and phylogeny Phylogenetics In biology, phylogenetics is the study of evolutionary relatedness among groups of organisms , which is discovered through molecular sequencing data and morphological data matrices... of the Bryopsida. |
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