moss - Classification of mosses, Habitat, Cultivation, Commercial use

A small, spore-bearing, non-vascular plant of the Class Musci, related to liverworts and hornworts. Mat- or cushion-forming, the visible plant is the gametophyte which begins as an undifferentiated body (thallus) or, more usually, a threadlike structure (protonema) reminiscent of a green alga. This develops into the more familiar plant with stems, simple, delicate leaves, and multicellular rhizoids. The sporophyte consists of a stalked capsule containing a central pillar and numerous spores. The capsule matures after the stalk has elongated, and the spores are released via pores, slits or, in some species, explosively. Mosses are found almost everywhere, most often in damp, shady places. However, some species are better able to withstand drying out, and a few even inhabit very dry places such as walls.

?Moss
"Muscinae" from Ernst Haeckel's Kunstformen der Natur, 1904
Scientific classification
Kingdom: Plantae Division: Bryophyta Class: Bryopsida
Subclasses
Sphagnidae Andreaeidae Tetraphidae Polytrichidae Archidiidae Buxbaumiidae Bryidae

Mosses are small, soft plants that are typically 1-10 cm tall, occasionally more. At certain times mosses produces spore capsules which may appear as beak-like capsules borne aloft on thin stalks. each chromosome exists with a partner that contains the same genetic information) whilst mosses (and other bryophytes) have only a single set of chromosomes (haploid, i.e. 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.

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). From the tips of stems or branches develop the sex organs of the mosses.

Mosses can be either dioicous (compare with 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 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.

Classification of mosses

Mosses were traditionally grouped with the liverworts and hornworts in the Division Bryophyta (bryophytes), within which the mosses made up the class Musci.

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. These large mosses form extensive acidic bogs in peat swamps. Aside from this character, the unique branching, thallose (flat and expanded) protonema, and explosively rupturing sporangium place it apart from other mosses. 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. over 95% of moss species belong to this subclass.

Habitat

Mosses are found chiefly in areas of low light and dampness; Mosses are common in wooded areas and at the edges of streams. Such aquatic or semi-aquatic mosses can greatly exceed the normal range of lengths seen in terestial mosses.

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. 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 gardening. In old temple gardens, moss can carpet a forest scene. 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. Samples of moss were installed in the cracks between wood slats.

Commercial use

There is a substantial market in mosses gathered from the wild. Decaying moss in the genus Sphagnum is also the major component of peat, which is "mined" for use as a fuel, as a horticultural soil additive, and in smoking malt in the production of Scotch whisky. In World War II, Sphagnum mosses were used as first-aid dressings on soldiers' wounds, as these mosses are highly absorbant and have mild antibacterial properties.

In rural 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.

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