To understand what mosses are, you need to study the oldest group of plants. This group is of the highest type, isolated and large. Nowadays, there are almost 30 thousand species of mosses on the entire planet.
Classification
Botanists discovered and studied all known species of bryophytes, the classification of which is based on differences in morphological structure, distribution methods and structure of spore capsules. The bryophyte division can conditionally be subdivided into the following classes: deciduous, hepatic, and anthocerotic mosses.
Deciduous mosses
What are leafy mosses? They are also called bryopsids. This is a large class with about 15 thousand species. Representatives of this group are recognized as the most highly developed of all plants in this department. Bryopsids are very diverse, both in shape and in size. Sometimes they reach considerable size. The most viable stage of their existence is the gametophyte. The plant looks like a stalk with single-layer leaves arranged in a spiral. Bryopsids reproduce by spores. They are common in the tundra, marshy and humid areas. Representatives: cuckoo flax, sphagnum moss.
Liver mosses
What are hepatic mosses (liverworts)? They number about 8.5 thousand species and are divided into two subclasses: marchantium and Jungermannian liverworts. The predominant viable stage is the gametophyte. Externally, the plant resembles a flattened "stem" with leaves along. Propagated by spores with the help of an elater (special spring). Liverworms are common in tropical and temperate-humid climates. Typical representatives: hairy blepharostroma, marchanthus polymorphic, barbilophosia bulbous, ciliary ptidium.
Antocerotic Mosses
What are anthocerotic mosses? Specialists often regard this class of mosses as a subclass of hepatic mosses. It includes almost 300 species.
The sporophyte stage predominates in the
life cycle . Externally, the plant looks like a rosette-like or lobed thallus. These mosses are found in climatic zones of moderate humid and tropical type. The representative of the class is anthoceros.
Generalized characteristics of mosses
So what are mosses? These are low-growing plants, the height of which can vary from 1 mm to 60 centimeters. They grow on tree trunks, on the walls of houses, on the ground, in fresh waters and swamps. Due to salt intolerance, plants are not found in the seas and on saline soils. Most often, the structure of mosses is very simple - stems and leaves. But the roots of the plants in question are absent altogether. They absorb water and nutrients with rhizoids or with the whole body. Adaptation to terrestrial existence has led to the appearance of integumentary and mechanical tissues, as well as new cells that perform a conducting function. This plant is a perennial, most often small (only a few mm high), rarely large (up to 60 cm). His body looks like a thallus (anthocerotic or separate liverworts) or is divided into a “stem” and “leaves”. Attachment to the substrate and absorption of water is carried out by outgrowths of cells, the so-called rhizoids (as a rule, they lack a conducting system).
also not intricate. These are large light green or slightly reddish jackets. They have erect “stems”, with bundle-like foliage “branches” located. Without rhizoids, the stalk of the moss is erect (gradually dying from below), leafy in several rows, with numerous leafy lateral processes that are collected at the top of the stem in a dense head. Throughout the rest of the stem, the branches are collected in bunches. The latter consist of 3-13 branches hanging and spaced from the stem. At the top, the “branches” are shortened and assembled into a tight head. Colorless aquifers with pores make up the outer layer of the “stem”.
Single-layer “leaves” of sphagnum include cells of two types: photosynthetic and aquifers. The former are worm-shaped and contain chloroplasts located between aquifers. There are many such cells, which allows the sphagnum to absorb a large amount of water. Sphagnum sporophyte is a rounded box in which spores appear, with a lid. When the spores mature, the pressure inside the capsule increases, as a result of which the lid opens, and the mature spores are thrown out. This process takes place in warm weather for better distribution of spores.
What are green mosses? Their bright representatives include cuckoo flax. Its “stem” is covered with hard, dark green awl-shaped “leaves”. It has rhizoids and grows up to 30-40 cm. The leaves of the moss are bent and erect, with an elongated membranous vagina and a vein protruding from the apex. "Stem" has a primitive conductive system and dioecious gametophytes. The top of the "stems" ends with anteridia and archegonies. After fertilization, a sporophyte develops from the zygote, which is a box on a long stalk for the maturation of haploid spores in it. The box is covered with a falling cap with thin, lowered hairs, like linen yarn. A box of moss is divided into a lid, neck and urn. Inside the box is “hidden” a column filled with sterile cells. Around the column is sporangia. The urn and the lid border on a ring consisting of cells with thickened walls. This ring is responsible for dropping the urn and its separation from the lid.
Moss propagation methods
The sexual generation in the life cycle of a plant prevails over asexual. The reproductive organs of moss are formed directly on its body. These are the above-mentioned archegonies and anteridia. Archegonia are responsible for the formation and development of one immovable female gamete, and antheridia - for many male gametes. In a fertilized female gamete (the condition is the presence of water), the asexual generation of moss - sporophyte begins to develop. This is a kind of box on the leg attached to the body of the moss. It contains many spores that are able to germinate under favorable conditions, forming a new plant. Some species are able to reproduce vegetatively. At the same time, the thallus is separated from the adult body, which attaches itself in close proximity to the plant, and begins its independent existence and reproduction.
Moss spread
It is more difficult to determine where there is no moss than to tell where moss grows. This representative of the flora is distributed almost everywhere - from the tropics to the polar regions. In tropical regions, moss grows mainly in mountainous terrain and in forests, i.e., where high humidity prevails. Sometimes the soil covered with mosses is also found in arid territory, since this plant has the ability to temporarily stop its activity in the dry period, and with the appearance of moisture to resume it. Basically, mosses predominate in the temperate and subarctic zones of the northern hemisphere.
Moss and its meaning
The importance of mosses in nature is enormous. Firstly, thanks to these representatives of the plant world, the landscape water balance is regulated, because they are able to accumulate large reserves of moisture in the thallus. Secondly, the moss plant creates a special biocenosis, especially in areas where it completely covers the soil. In addition, this group has the ability to accumulate and retain radiation. The importance of mosses for animals is also great, because bryophytes are the main type of food for some individuals. Yes, and in human life, this plant also plays an important role. So, many types are effectively used in pharmacology. And peat formed after the death of mosses is used as fuel.