Mosses are small flowerless plants that usually grow in dense green clumps or mats, in damp or shady locations. The individual plants are usually composed of simple, one-cell thick leaves, covering a thin stem that supports them but does not conduct water and nutrients (nonvascular).
Since moss gametophytes have no vascular system to transport water through the plant or waterproofing systems to prevent tissue water from evaporating, they must have a damp environment in which to grow, and a surrounding of liquid water to reproduce. Since mosses are autotrophic they require enough sunlight to conduct photosynthesis. Shade tolerance varies by species, just as it does with higher plants. In most areas, mosses grow chiefly in areas of dampness and shade, such as wooded areas and at the edges of streams; but they can grow anywhere in cool damp cloudy climates, and some species are adapted to sunny, seasonally dry areas like alpine rocks or stabilized sand dunes. Wherever they occur, mosses require high levels of moisture to survive because of the lack of a vascular system, and the need for liquid water to complete fertilisation. Many mosses can survive desiccation, sometimes for months, returning to life within a few hours of rehydration.
Mosses are commonly confused with lichens, hornworts, and liverworts. Lichens may superficially look like mosses, and have a common names that includes the word moss, but are not related to mosses. Mosses, hornworts, and liverworts are collectively called “bryophytes”. Bryophytes share the properties of not having vascular tissue and producing spores instead of flowers and seeds. Bryophytes have the haploid gametophyte generation as the dominant phase of the life cycle. This contrasts with the pattern in all vascular plants (seed plants and pteridophytes), where the diploid sporophyte generation is dominant.
Mosses are in the phylum (division) Bryophyta, which formerly also included hornworts and liverworts. These other two groups of bryophytes are now placed in their own divisions. There are approximately 12,000 species of moss classified in the Bryophyta.The main commercial use of mosses is for decorative purposes, such as in gardens and in the florist trade. Traditional uses of mosses included as insulation and for the ability to absorb liquids up to 20 times their weight. Slider shot of the sun shining through the shrubs in a bushes, with moss in the foreground.