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MOSSES, (class Musci),
the common name for members of a division of plants called Bryophyta which are native to the entire land areas of the world, and grow on rocks, soil, the bark of trees, in shallow streams and bogs (sphagnum moss, which becomes peat). Moss plants consist of small, slender stalks and leaves; vascular tissue is not present. Lacking true roots, the functions of underground support and conduction are carried on by filamentous structures called rhizoids. |
Mosses have an interesting and complex system of propagation. The organs of sexual reproduction are called antheridia (containing sperms) and archegonia (the egg) and are borne on the gametophyte, which is an independent leafy plant. Fertilization can take place only when the plants are wet; after which the egg grows into a sporophyte consisting of a base or foot, embedded in gametophyte tissue; a stalk that is usually long and hairlike; and a terminal capsule. In most species this is covered by a small-toothed lid containing numerous spores that are either released explosively by special peristome teeth or, under suitable conditions, germinate by forming slender underground filaments called protonemata which produce small buds and give rise to gametophyte plants. |
| Mosses also make gametophy- tes from
such specialized vegetative organs as bulbils, produced by rhizoids; gemmae,
formed on leaves or stems; and secondary protonemata produced by rhizoids
or wounded portions of the leafy shoot (known as Alternation of Generations,
which is also used by the other divisions of bryophytes - liverworts
and hornworts) when the embryo from the sexual plant matures into a small
asexual plant that remains attached to and dependent on the sexual plant.
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| The asexual plant produces spores similar
to those formed by lower plants and are spread by wind and other carriers
to make new sexual plants. And the sexual organs of bryophytes are multicellular.
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There are about 15,000 species of mosses, and about 8,500 species of liverworts world-wide. They are very common in rainforest, and create favourable habitat for epiphytics such as the Kangaroo fern, finger ferns and the shiny film-fern which colonise tree trunks and rocks. |
Kangaroo fern. |
