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Mosses, hornworts, and liverworts were once placed together in the division Bryophtya. Molecular evidence, however, led to a major revision of the group’s taxonomy. Mosses alone now represent the division Bryophyta, and hornworts and liverworts are placed in the divisions Anthocerotophyta and Marchantiophyta, respectively. The term bryophyte, however, is still used informally to refer to these simple terrestrial plants. Classification of the liverworts…

The fossil record of bryophytes is poor. Some fossils, however, show a morphology, size, and cellular detail that characterize bryophytes, and the specimens are treated as fossil bryophytes. Since sex organs and attached sporophytes are absent in nearly all fossil material and because the gametophytes of some living vascular plants resemble the gametophores of some bryophytes, the assignment of…

The gametophyte form shows several developmental stages: the spore, the protonema, and the gametophore, which produces the sex organs. Spores of bryophytes are generally small, 5–20 micrometres on the average, and usually unicellular, although some spores are multicellular and considerably larger. Spores have chlorophyll when released from the sporangium. They are generally hemispheric, and the surface is often elaborately ornamented.…

Some bryophytes are unusually tolerant of extended periods of dryness and freezing, and, upon the return of moisture, they rapidly resume photosynthesis. The exact mechanism involved remains controversial. Many bryophytes grow on soil or on the persistent remains of their own growth, as well as on living or decomposing material of other plants. Some grow on bare rock…

Bryophytes generate their nutrient materials through the photosynthetic activity of the chlorophyll pigments in the chloroplasts. In addition, most bryophytes absorb water and dissolved minerals over the surface of the gametophore. Water retention at the surface is assisted by the shape and overlapping of leaves, by an abundance of rhizoids, or by capillary spaces among these structures. Water…

The life cycle of bryophytes consists of an alternation of two stages, or generations, called the sporophyte and the gametophyte. Each generation has a different physical form. When a spore germinates, it usually produces the protonema, which precedes the appearance of the more elaborately organized gametophytic plant, the gametophyte, which produces the sex organs. The protonema is usually threadlike and is highly branched in…

The peat moss genus Sphagnum is an economically important bryophyte. The harvesting, processing, and sale of Sphagnum peat is a multimillion-dollar industry. Peat is used in horticulture, as an energy source (fuel), and, to a limited extent, in the extraction of organic products, in whiskey production, and as insulation. Bryophytes are very important in initiating soil formation on barren terrain, in maintaining soil moisture, and…

Bryophytes are distributed throughout the world, from polar and alpine regions to the tropics. Water must, at some point, be present in the habitat in order for the sperm to swim to the egg. Bryophytes do not live in extremely arid sites or in seawater, although some are found in perennially damp environments within arid regions and…

Thallose bryophytes vary in size from a length of 20 cm (8 inches) and a breadth of 5 cm (2 inches; the liverwort Monoclea) to less than 1 mm (0.04 inch) in width and less than 1 mm in length (male plants of the liverwort Sphaerocarpos). The thallus is sometimes one cell layer thick through most of its…