Mosses

Mosses, common name for members of a division (phylum) 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 sperm and eggs, 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 hair-like; and a terminal capsule. The capsule, which in most species is covered by a small-toothed lid, contains numerous spores. The spores are released either 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 new 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 damaged parts of the leafy shoot (see Alternation of Generations). The division is commonly divided into three classes: the liverworts, the hornworts, and the mosses.

Many moss-like 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 mossy saxifrage. Rock moss is a common name applied to several lichens that grow on rocks. Plants known as clubmosses are related to the ferns. Spanish moss is a flowering plant that grows as an epiphyte in trees in the southern regions of the United States and in the West Indies.

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