The Bryophyta include the simplest and most primitive members of Embryophyta. They are the first plants to grow on land. In bryophyta, the gametophyte is the conspicuous, longer-lived phase of the life-cycle as compared with the sprorophyte generations. The gametophyte plant body is either is flattened thallus or a definite rootless leafy shoot. Roots are altogether absent and their function is taken up by unicellular or multicellular rhizoids which arise from the ventral surface of the thallus. The life cycle shows a distinct heteromorphic alternation of generation. Sxeual reproduction is of oogamous type. The Sxeual organs are multicellular which are surrounded by a sterile sheath. The male reproductive organ is antheridium consisting of a sterile jacket layer which encloses a mass of antherozoid mother cells. Each of which gives rise to a single ciliated motile antherozoid. The female reproductive organ is the archegonium. The archegonium is a multicellular, flask-shaped organ consisting of neck canal cells, a ventral canal cell and an egg. The venter wall enlarges with the developing embryo to form a protective envelope, the calyptra. External water is essential for fertilization. The sporophyte is a simple structure consisting of a foot, seta and a terminal spore producing capsule. The sporophyte is totally dependent on the gemetophyte for its water and mineral nutrition. The spores are morphologically all alike in size and form. Spore germinates to produce a protonemal phase which leads to the formation of adult type of gametophytic plant.
Proskauer (1957) divided bryophyta into 3 main classes -
1. Hepaticopsida (Hepaticae) -Thallus dorsiventral, may be thalloid or foliose; rhizoids unicellular; scales present; Sxeual organs on the dorsal side of the thallus; columella absent in capsule; stomata absent on the wall of capsule; spores develop from endothecium of capsules e.g. Riccia, Merchantia
2. Anthocerotopsida (Anthocerotae) -he gametophyte is thalloid and dorsiventral; rhizoids without septa; scales absent; Sxeual organs embedded on the dorsal surface of the gametophyte; capsule with central columella; elaters present; sporogonium elongated and cylindrical with cell wall containing chlorophyll; spores develop from amphithecium of capsule e.g. Anthoceros
3. Bryopsida (Musci) -Gametophyte erect and leafy; rhizoids multicellular with oblique septa; Sxeual organs on apical portion of gametophyte; Sporophyte differentiated into foot, seta and capsule; seta quite long; capsule wall having stomata; spore sac usually separated from the capsule wall by air space; elaters absent; columella present; spores develop from outer layer of endothecium; capsule oval with operculum and peristomial teeth e.g. Funarea, Sphagnum