<P> Between 510 - 630 million years ago, land plants evolved from aquatic plants, specifically green algae . Molecular phylogenetic studies conclude that bryophytes are the earliest diverging lineages of the extant land plants . They provide insights into the migration of plants from aquatic environments to land . A number of physical features link bryophytes to both land plants and aquatic plants . </P> <P> Distinct adaptations observed in bryophytes have allowed plants to colonize Earth's terrestrial environments . To prevent desiccation of plant tissues in a terrestrial environment, a waxy cuticle covering the soft tissue of the plant provides protection . The development of gametangia provided further protection specifically for gametes . They also have embryonic development which is a significant adaptation seen in land plants and not green algae . While bryophytes have no truly vascularized tissue, they do have organs that have specific functions, similar to those functions of leaves and stems in higher level land plants . </P> <P> Bryophytes also exhibit connections to their aquatic ancestry . They share various features with their green algae ancestors . Both green algae and bryophytes have chlorophyll a and b, and the chloroplast structures are similar . Like algae and land plants, bryophytes also produce starch and contain cellulose in their walls . </P> <P> Bryophytes depend on water for reproduction and survival . A thin layer of water is required on the surface of the plant to enable the movement of sperm between gametophytes and the fertilization of an egg . </P>

Cell wall of bryophyta is made up of