There are about 20,000 species of Bryophytes, the plants that lack vascular tissue. They are found throughout the world. Although more prevalent in moist and shady areas, Bryophytes can be found in alpine regions, where they are subjected to freezing, and some in deserts, where they are desiccated most of the time.
Many Bryophytes are highly specialized, and found in restricted habitats.
Associations of Bryophyes with mychorrizae are common. Impact on Structure Bryophytes lack vascular tissues so Bryophytes must absorb all water and nutrients at the surface and pass them from cell to cell. A few have modified water transport cells, call hydroids, and a few have solute conducting cells, called leptoids, but this is rare. Depending on cell to cell diffusion for transport places size restriction on Bryophytes. Gemmae propagules Fragmentation Gametophyte generation is the predominant and assimilative stage.