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Frullania pycnantha, Liverwort
© John Braggins · 8
Frullania pycnantha, Liverwort
Thuidiopsis, Moss
© Matt von Konrat, 2004 · 9
Thuidiopsis, Moss
Hornworts, liverworts, and mosses - commonly referred to as bryophytes - are considered to be a pivotal group in our understanding of the origin of land plants because they are believed to be among the earliest diverging lineages of land plants. Mosses, liverworts and hornworts are found throughout the world in a variety of habitats, from the harsh environs of Antarctica to the lush conditions of the tropical rainforests. Bryophytes are unique among land plants in that they possess an alternation of generations, which involves a dominant, free-living, haploid gametophyte alternating with a reduced, generally dependent, diploid sporophyte. Bryophytes are small, herbaceous plants that grow closely packed together in mats or cushions on rocks, soil, or as epiphytes on the trunks and leaves of forest trees. Bryophytes are remarkably diverse for their small size and are well-adapted to moist habitats and flourish particularly well in moist, humid forests like the fog forests of the Pacific northwest or the montane rain forests of the southern hemisphere.

Significance of bryophytes
Bryophytes have a significant role in contributing to nutrient cycles, providing seed-beds for the larger plants of the community, and form microhabitats for insects and an entire array of microorganisms. Bryophytes are also very effective rainfall interceptors, and the overwhelming abundance of epiphytic liverworts in "cloud" or "mossy" forest zones is considered an important factor in eliminating the deteriorating effect of heavy rains, including adding to hill stability and helping to prevent soil erosion. The chemical compounds of some liverworts are also particularly interesting because they have important biological activities, for example, against certain cancer cell lines, anti-bacterial properties, anti-microbial, anti-fungal, and muscle relaxing activity.

Over the last decade, recent advances in DNA sequencing technology and analytical approaches to phylogenetic reconstruction, including the use of ultra-structural, morphological and anatomical data, have enabled unprecedented progress toward our understanding of plant evolution. A growing consensus suggests that the bryophytes possibly represent three separate evolutionary lineages, which are today recognized as mosses (phylum Bryophyta), liverworts (phylum Marchantiophyta) and hornworts (phylum Anthocerotophyta).

  • Mosses (Bryophyta)
    The greatest species diversity in bryophytes is found in the mosses, with estimates of the number of species ranging from 10,000 to 15,000. Higher-level classification of the mosses remains unresolved with considerable difference of opinion on the names of the major groups. However, generally four major groups or classes are recognised. These include: Sphagnopsida (peat or Sphagnum mosses), Andreaeopsida (rock or lantern mosses), Polytrichopsida (nematodontous mosses), and the Bryopsida (arthrodontous mosses). The Sphagnum mosses are one of the most ecologically and economically important groups of bryophytes. The class Bryopsida accounts for the largest and most diverse groups within the mosses with over 100 families.

  • Liverworts (Marchantiophyta)
    The estimated number of liverwort species range from 6000 to 8000. Traditionally, liverworts have been subdivided into two major groups or classes based, partially, on growth form. The class Marchantiopsida, includes the well-known genera Marchantia, Monoclea, Lunularia, and Riccia, and has a complex thalloid organisation. The class Jungermanniopsida represents an estimated 85% of liverwort species and shows an enormous amount of morphological, anatomical and ecological diversity; plants with leafy shoot systems are the most common growth form in this class, e.g., Frullania, Jubulopsis, Cololejeunea, and Radula.

  • Hornworts (Anthocerotophyta)
    Hornworts get their name from their long, horn-shaped sporophytes and are the smallest group of bryophytes with only approximately 100 species. Hornworts resemble some liverworts in having simple, unspecialized thalloid gametophytes, but they differ in many other characters. Hornworts differ from all other land plants in having only one large, algal-like chloroplast in each thallus cell.

Scientific Name Common Name
Plantae Land Plants
Embryophytes Green plants

Geographic distribution

Links to other sites

This page written and compiled by:
William R Buck New York Botanical Gardens,
Bernard Goffinet University of Connecticut,
John J Engel The Field Museum, Chicago,
Matt von Konrat The Field Museum, Chicago, and
John Pickering University of Georgia, Athens.

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