Phylum Bryophyta

Almost every land environment is home to at least one species of moss in the phylum Bryophyta (brie-AHF-uh-tuh). The thick green carpets of moss on shady forest floors actually consist of thousands of moss gametophytes. Each gametophyte is attached to the soil by rootlike structures called rhizoids (RIE-ZOYDZ). Unlike roots, rhizoids do not have vascular tissue. But rhizoids do function like roots by anchoring the moss and by absorbing water and inorganic nutrients.

Moss gametophytes are usually less than 3 cm (1.2 in.) tall. The moss sporophyte grows up from the top of the gametophyte, as shown in Figure 28-4. Gametophytes may be male, may be female, or may contain both male and female reproductive parts.

Mosses are called pioneer plants because they are often the first species to inhabit a barren area. Mosses gradually accumulate inorganic and organic matter on rock surfaces, creating a layer of soil in which other plants can grow. In areas devastated by fire, volcanic action, or human activity, pioneering mosses can help trigger the development of new biological communities. They also help prevent soil erosion by covering the soil surface and absorbing water.

figure 28-4

Moss sporophytes (thin, brown stalks) depend on the gametophytes (green, "mossy" parts) to which they are attached, because sporophytes do not undergo photosynthesis.

figure 28-4

Moss sporophytes (thin, brown stalks) depend on the gametophytes (green, "mossy" parts) to which they are attached, because sporophytes do not undergo photosynthesis.

figure 28-5

A peat farmer cuts blocks of peat, produced from moss of the genus Sphagnum, to heat his farmhouse in County Clare, Ireland.

figure 28-5

A peat farmer cuts blocks of peat, produced from moss of the genus Sphagnum, to heat his farmhouse in County Clare, Ireland.

Peat moss (of the genus Sphagnum) is a major component of bogs in northern parts of the world. Peat moss produces an acid that slows down decomposition in the swamplike bogs. Compression and chemical breakdown in peat bogs produces peat, which consists of partially decomposed plant matter. In many northern European and Asian countries, peat is mined and dried for use as fuel, as shown in Figure 28-5. Dried peat moss is widely used to enhance the water-retaining ability of potting and gardening soils. Dried peat moss is also used by florists to pack bulbs and flowers for shipping.

Word Roots and Origins liverwort from the familiar liver (body organ) and the Old English wort, meaning "herb"

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