General characteristic features

Bryophytes are simplest land-dwelling cryptogams, mostly confined to moist, shady habitats, though a few (Riella, Ricciocarpus) are aquatic. Crucially, the conspicuous, long-lived phase of the life cycle is the gametophyte, not the sporophyte. In liverworts and hornworts the gametophyte is a flat, undifferentiated thallus that grows prostrate on the ground and attaches by rhizoids (of two kinds — smooth-walled and pegged) plus multicellular scales; in mosses the gametophyte is more advanced, with an erect axis bearing leaf-like structures and multicellular rhizoids. Because bryophytes entirely lack conducting tissue (xylem and phloem), they are also called 'non-vascular cryptogams'.

Vegetative reproduction happens through adventitious buds (Riccia fluitans), tubers (Anthoceros), small detachable brood bodies (Bryopteris fruticulosa), or specialised propagative structures called gemmae (Marchantia). The sporophyte is always dependent on the gametophyte and is differentiated into three recognisable parts: a basal foot embedded in the gametophyte (through which water and nutrients pass to the sporophyte), a seta, and a capsule. Inside the capsule, diploid spore mother cells undergo meiosis to produce haploid spores — bryophytes are homosporous — and in some genera thread-like elaters assist spore dispersal (e.g. Marchantia). …