Even in other bryophytes, the sporophyte is persistent and disperses spores over an extended period. the diploid body) are very short-lived, withering away not long after releasing spores. Another unusual feature of the liverwort life cycle is that sporophytes (i.e. In the more familiar seed plants, the haploid generation is represented only by the tiny pollen and the ovule, while the diploid generation is the familiar tree or other plant.
This contrasts sharply with the pattern exhibited by nearly all animals and by most other plants. Cells in a typical liverwort plant each contain only a single set of genetic information, so the plant's cells are haploid for the majority of its life cycle. Liverworts have a gametophyte-dominant life cycle, with the sporophyte dependent on the gametophyte. The overall physical similarity of some mosses and leafy liverworts means that confirmation of the identification of some groups can be performed with certainty only with the aid of microscopy or an experienced bryologist. In addition, 90% of liverworts contain oil bodies in at least some of their cells, and these cellular structures are absent from most other bryophytes and from all vascular plants. Other differences are not universal for all mosses and all liverworts but the lack of clearly differentiated stem and leaves in thallose species, or in leafy species the presence of deeply lobed or segmented leaves and the presence of leaves arranged in three ranks, all point to the plant being a liverwort. Liverworts can most reliably be distinguished from the apparently similar mosses by their single-celled rhizoids. Some species can be a nuisance in shady green-houses or a weed in gardens. They are distributed globally in almost every available habitat, most often in humid locations although there are desert and arctic species as well. However, certain species may cover large patches of ground, rocks, trees or any other reasonably firm substrate on which they occur. Liverworts are typically small, usually from 2-20 mm wide with individual plants less than 10 cm long, and are therefore often overlooked. Other differences are not universal for all mosses and liverworts, but the occurrence of leaves arranged in three ranks, the presence of deep lobes or segmented leaves, or a lack of clearly differentiated stem and leaves all point to the plant being a liverwort. Leafy liverworts also differ from most (but not all) mosses in that their leaves never have a costa (present in many mosses) and may bear marginal cilia (very rare in mosses). Leafy species can be distinguished from the apparently similar mosses on the basis of a number of features, including their single-celled rhizoids. Some of the more familiar species grow as a flattened leafless thallus, but most species are leafy with a form very much like a flattened moss. It is estimated that there are 6000 to 8000 species of liverworts, though when Neotropical regions are better studied this number may approach 10,000. Like other bryophytes, they have a gametophyte-dominant life cycle, in which cells of the plant carry only a single set of genetic information.
The Marchantiophyta Template:Audio-IPA are a division of bryophyte plants commonly referred to as hepatics or liverworts.
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