Liverworts are non-vascular plants in the Class Marchantiopsida, formerly known as the Hepaticae. They are colloquially called hepatics. The Division Bryophyta consists of liverworts together with mosses and hornworts.
Most liverworts consist of a prostrate, flattened, branching structure called a thallus (plant body). These liverworts are termed thallose liverworts. Other liverworts produce flattened stems with overlapping scales and are called leafy liverworts or scale liverworts.
Ancient beliefs included that liverworts cured diseases of the liver, hence the name. An unrelated flowering plant, Hepatica, is sometimes mistakenly called a liverwort, due to the similarity with the common name, "hepatics".
The liverwort gametophyte is either a leafy stem or a thallus, ie, a flat, leafless expanse of cells (resembling the lobes of the liver, hence the name).
Most leafy liverworts have stems with 2 lateral rows of leaves; many species have a third row of reduced leaves on the underside of the stem.
Liverwort sporophytes have a foot, embedded into the gametophyte tissues, and a spore capsule, normally raised above the gametophyte by a fragile stalk and persisting for only a day or so.
Early studies had suggested that mosses were sister to vascular plants, thus the conducting tissue in the centre of the stem in some moss gametophytes could be thought of "homologous" to the vascular tissue in the sporophytes of vascular plants (e.g.
In a few earlier studies the liverworts appeared not to be monophyletic (Bopp and Capesius 1998 and references).
Liverworts (Marchantiophyta) are monophyletic, despite earlier suggestions that they might not be (Quandt and Stech 2003 for references).
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