Moss

Moss, common name for members of a division of plants (see Bryophytes), native to the entire land area of the world. Mosses grow on soil, rocks, and the bark of trees, and in bogs and shallow streams. Moss plants consist of small, slender stalks and leaves; vascular tissue is not present. They lack true roots, the functions of underground support and conduction being carried on by filamentous structures called rhizoids. The organs of sexual reproduction, called antheridia and archegonia, contain sperms and egg, respectively, and are borne on the gametophyte, which is an independent leafy plant. Fertilization can take place only when the plants are wet; after fertilization, the egg grows into a sporophyte. The sporophyte consists of a base, or foot, embedded in gametophyte tissue; a stalk that is usually long and hairlike; and a terminal capsule. The capsule, which in most species is covered by a small-toothed lid, contains numerous spores. The spores are either released explosively or by special peristome teeth. Under suitable conditions they germinate by forming slender underground filaments called protonemata. Small buds produced by protonemata give rise to gametophyte plants. Mosses also produce gametophytes from such specialized vegetative organs as bulbils, produced by rhizoids; gemmae, produced on leaves or stems; and secondary protonemata, produced by rhizoids or wounded portions of the leafy shoot (see Alternation of Generations). The division is commonly divided into three classes: the liverworts, the hornworts, and the mosses.

Many mosslike plants, unrelated to the moss division, are commonly called mosses. These include Irish moss, or carrageen, which is a red alga. Iceland moss is a common name applied to a lichen and to a flowering plant also known as wild stonecrop. Rock moss is a common name applied to several lichens that grow on rocks, and to widow's-cross. Plants known as club moss are related to the ferns. Spanish moss, or long moss, is a flowering plant that grows as an epiphyte on tree trunks in the southern regions of the United States and in the West Indies.

Scientific classification: Mosses make up the division Bryophyta. The liverworts make up the class Hepaticae, the hornworts the class Anthocerotae, and the mosses the class Musci.