A phylum comprising the liverworts—simple plants that lack vascular tissue and possess rudimentary rootlike organs (rhizoids). Liverworts occur in moist situations (including fresh water) and as epiphytes on other plants. Like the mosses (see bryophyta), liverworts show marked alternation of generations between haploid gamete-bearing forms (gametophytes) and diploid spore-bearing forms (sporophytes), the latter being dependent on the former for nutrients, etc. The plant body (gametophyte) may be a thallus, growing closely pressed to the ground (thallose liverworts, e.g. Pellia), or it may bear many leaflike lobes (leafy liverworts). It gives rise to leafless stalks bearing capsules (sporophytes). Spores formed in the capsules are released and grow to produce new plants. Molecular studies show that the liverworts are the sister clade to all other land plants, including the mosses, with which they were formerly placed (in the class Hepaticae) in the phylum Bryophyta.

http://lifeofplant.blogspot.co.uk/2011/03/liverworts.html Introduction to liverworts, from the Plant Life website