Bryophyta

Bryophyta (Bryophyta), a class of archegoniate plants (about 18,000 species), divided into two subclasses: 1) leafy Bryophyta (Musci) and 2) liverwort Bryophyta (Hepaticae). The former have a stem growing from the apex and flat leaves attached to it; roots are absent and replaced by hairs (rhizoids) extending from the lower part of the stem. The latter do not have a clear division into stem and leaf; their body often resembles a lobed green plate attached by rhizoids on one side to the substrate. (They are called liverwort Bryophyta due to some resemblance to the shape of the liver.) In reproduction, Bryophyta form sexual organs: female ones—archegonia in the form of a bottle with an egg in the lower swollen part, and male ones—antheridia in the form of sacs containing a large number of spermatozoa. After fertilization, the egg grows and forms a body called a sporogonium. It usually consists of a stalk, which is a continuation of the stem, and an upper swollen part, or capsule, in which spores develop. From these, a new Bryophyta plant grows. The size of mosses is usually small (several cm), but they often grow in large quantities forming dense turfs and thickets. They are particularly important in bog vegetation and in the tundra. Bryophyta have no medical significance except for peat moss (Sphagnum), which is sometimes used as a material for absorbing secretions from wounds, etc. Sphagnum also has certain hygienic significance as a common lining in residential wooden buildings. Bryophyta are also sometimes called certain other plants, such as reindeer moss (Cladonia), Iceland moss (Cetraria), oak moss (Evernia), beard moss (Usnea), etc. However, they only have external similarity to Bryophyta and belong to another class of plants—lichens (see).