Liverwort

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Liverwort, common name for members of a phylum of bryophytes, a group of usually inconspicuous plants. There are two major liverwort types: thallose liverworts and leafy liverworts. The common name, liverwort, derives from the fact that some thallose are liver-shaped in outline. About 300 genera and 6000 species of liverworts occur throughout the moist temperate to tropical regions.

Liverworts are characterized by a free-living, conspicuous, sexual (gametophytic) generation, to which is attached a usually inconspicuous, asexual (sporophytic) generation. The gametophyte may be a leafless, flattened thallus; more often it is leafy, with the leaves produced in three rows, of which one is smaller than the others. The lower surfaces of the gametophytes produce unicellular, rootlike structures called rhizoids, which serve for attachment and external water transport. The sporophytes of liverworts are simple structures consisting of a foot embedded in the gametophyte and a spore-producing capsule that opens by splitting lengthwise. Often a delicate stalk, or seta, grows between the foot and capsule and serves to elevate the capsule to aid in the dispersal of spores. The spores are produced in great numbers, and they germinate directly into new gametophytes.

Mosses are often confused with liverworts. The sporophytes of mosses are generally similar in appearance to those of liverworts but are much more complex, the spores being released through teeth at the tip of the capsule.

Scientific classification: Liverworts make up the class Hepaticae of the division Bryophyta.

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