Bryophyte

Bryophyte is a traditional name used to refer to all embryophytes (land plants) that are non-vascular plants, namely the mosses, hornworts, and liverworts. The defining features of bryophytes are that their life cycles are dominated by the gametophyte stage, that their sporophytes are unbranched and that they do not have a true vascular tissue containing lignin, although some have specialized tissues for the transport of water. Bryophytes are usually considered to be a paraphyletic group and not a natural (monophyletic) group, although some studies have produced contrary results. Regardless of their status, the name is convenient and remains in use as an informal collective term. Bryophytes produce enclosed reproductive structures (gametangia and sporangia), but they produce neither flowers nor seeds, reproducing via spores. The term "bryophyte" comes from Greek βρύον, bryon, "tree-moss, oyster-green" + φυτόν – phyton "plant".

Like all land plants (embryophytes), bryophytes have life cycles with alternation of generations. In each cycle, a haploid gametophyte, each of whose cells contains a fixed number of unpaired chromosomes, alternates with a diploid sporophyte, whose cell contain two sets of paired chromosomes. Gametophytes produce haploid sperm and eggs which fuse to form diploid zygotes that grow into sporophytes. Sporophytes produce haploid spores by meiosis, that grow into gametophytes.

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