Liverworts
 
Liverworts are in the botanical division Marchantiophyta. There are about 9,000 species globally, and about 300 in Britain and Ireland.  They are found in most habitats except the sea and dry or very hot sunlit places.  Generally they prefer moister habitats and light to deep shade, often with acid soils.  Like mosses, the dominant life stage is the haploid gametophyte, which produces eggs and sperm, but it is now thought the liverworts and mosses are not closely related.
 
Liverworts are less often found (or noticed) in gardens than mosses. Jennifer Owen only recorded Marchantia polymorpha.1. The Sheffield BUGS project found only four species,2. while the Buckingham Palace survey3. listed 4 species outside greenhouses.
 
We can divide the garden liverworts into two groups:
 
 
“Thalloid” liverworts
 
Here the body of the plant is thalloid - that is forming a little, often lobed, strap-like form looking not unlike a miniature green liver – hence the name liverworts. Little mats of Marchantia polymorpha, the common or umbrella liverwort, live up to their name, being a frequent flowerpot, path-edge and greenhouse invader in damp soils. This is one of our larger liverworts, easily visible with the naked eye and characterised by a flattened thallus up to 10cm long, green in colour, with a pattern of polygonal markings and little umbrella-like reproductive structures called gametophores separated into female ones with star-like rays on a stalk (the umbrellas) and the male flattened discs. Both sexes do not occur on the same thallus.  Sperms shed by the male structures fertilise the female's eggs which are held under the star structures. The fertilised eggs develop into spore producing structures retained under the star, and are shed when ripe.
 
 
Another thalloid liverwort Pellia epiphylla (left) was found both in Sheffield gardens and at Buckingham palace. In this species both male and female structures are found on the same thallus, and the shiny black spore-producing diploid sporophyte is carried up above the thallus on a stem.
 
 
 
Marchantia polymorpha   Above: view of the thallus. 
 
Below left: with disc-like male gametophores.  Below right: star-shaped female gametophores.
Leafy liverworts
 
The leafy liverworts are structured as an elongate stem with leaves growing out from it.  They are more numerous than the thalloid species, especially in damp warm climates.  A common British and Irish species is bifid crestwort, Lophocolea bidentata, a delicate translucent, pale-green plant with bilobed leaves and shoot only 2-4mm wide, growing several centimetres long. The leaf lobes are drawn out to a narrow point. If you can turn it over to see the under-leaves, they are much smaller and also bilobed. 
 
 
 
Above: Dilated scalewort Frullania dilatata.  The specimen on the right is rather dry and darker in colour
 
If you look closely at your tree bark you may see purplish little branched leafy liverworts.  Frullania dilatata is one of the commonest, more usually found on ash, willow or poplar in well-lit surroundings and common throughout Britain. You will need a lens – the leaves are only about 1mm wide and 2.3mm long, with rounded lobes and large (for the plant that is) helmet-shaped lobules (small pouches or sacs next to the primary leaf lobe). Underleaves are present too.
 
 
 
References
 
1.  Owen, J. (2010) Wildlife of a garden: a thirty-year study.
 
2.  Smith, R.M, Thompson, K. Warren, P.H. and Gaston, K.J. (2010) Urban domestic gardens (XIII): Composition of the bryophyte and lichen floras, and determinants of species richness. Biological Conservation 143:873–882
 
3.  McClintock, D. (1963) Bryophytes and Fungi  Proc. S. Lond. ent. nat. Hist, Soc  1963 (2)  pp36-38
 
 
Page written by Penny Anderson, compiled by Steve Head
Bifid crestwort, Lophocolea bidentata
Liverworts
 
Liverworts are in the botanical division Marchantiophyta. There are about 9,000 species globally, and about 300 in Britain and Ireland.  They are found in most habitats except the sea and dry or very hot sunlit places.  Generally they prefer moister habitats and light to deep shade, often with acid soils.  Like mosses, the dominant life stage is the haploid gametophyte, which produces eggs and sperm, but it is now thought the liverworts and mosses are not closely related.
 
Liverworts are less often found (or noticed) in gardens than mosses. Jennifer Owen only recorded Marchantia polymorpha.1. The Sheffield BUGS project found only four species,2. while the Buckingham Palace survey3. listed 4 species outside greenhouses.
 
We can divide the garden liverworts into two groups:
 
“Thalloid” liverworts
 
Here the body of the plant is thalloid - that is forming a little, often lobed, strap-like form looking not unlike a miniature green liver – hence the name liverworts. Little mats of Marchantia polymorpha, the common or umbrella liverwort, live up to their name, being a frequent flowerpot, path-edge and greenhouse invader in damp soils. This is one of our larger liverworts, easily visible with the naked eye and characterised by a flattened thallus up to 10cm long, green in colour, with a pattern of polygonal markings and little umbrella-like reproductive structures called gametophores separated into female ones with star-like rays on a stalk (the umbrellas) and the male flattened discs. Both sexes do not occur on the same thallus.  Sperms shed by the male structures fertilise the female's eggs which are held under the star structures. The fertilised eggs develop into spore producing structures retained under the star, and are shed when ripe.
 
 
Marchantia polymorpha   Above: view of the thallus. 
 
Below left: with disc-like male gametophores.  Below right: star-shaped female gametophores.
 
 
Another thalloid liverwort Pellia epiphylla (left) was found both in Sheffield gardens and at Buckingham palace. In this species both male and female structures are found on the same thallus, and the shiny black spore-producing diploid sporophyte is carried up above the thallus on a stem.
 
Riccia sorocarpa Common crystalwort
 
This is a thalloid liverwort that grows in little irregular rosettes up to 2cm diameter. The thallus branches are  broader than long, and greyish-green in colour. They have a distinctive V-shaped groove down the middle of each thallus branch. There is a very narrow colourless margin to the thallus as well (visible through a hand lens).
 
This is a common species that you will find on the soil surface in fields, gardens, on bare waste ground, footpaths and gravel tracks.  There are other similar species in the same habitat but which are not as widespread in the country.
 
 
Leafy liverworts
 
The leafy liverworts are structured  as an elongate stem with leaves growing out from it.  They are more numerous than the thalloid species, especially in damp warm climates.  A common British and Irish species is bifid crestwort, Lophocolea bidentata, a delicate translucent, pale-green plant with bilobed leaves and shoot only 2-4mm wide, growing several centimetres long. The leaf lobes are drawn out to a narrow point. If you can turn it over to see the under-leaves, they are much smaller and also bilobed. 
 
 
 
Bifid crestwort, Lophocolea bidentata
 
Riccia sorocarpa Common crystalwort
 
 
This is a thalloid liverwort that grows in little irregular rosettes up to 2cm diameter. The thallus branches are  broader than long, and greyish-green in colour. They have a distinctive V-shaped groove down the middle of each thallus branch. There is a very narrow colourless margin to the thallus as well (visible through a hand lens).
 
This is a common species that you will find on the soil surface in fields, gardens, on bare waste ground, footpaths and gravel tracks.  There are other similar species in the same habitat but which are not as widespread in the country.
 
Above: Dilated scalewort Frullania dilatata.  The specimen on the right is rather dry and darker in colour
 
If you look closely at your tree bark you may see purplish little branched leafy liverworts.  Frullania dilatata is one of the commonest, more usually found on ash, willow or poplar in well-lit surroundings and common throughout Britain. You will need a lens – the leaves are only about 1mm wide and 2.3mm long, with rounded lobes and large (for the plant that is) helmet-shaped lobules (small pouches or sacs next to the primary leaf lobe). Underleaves are present too.
 
 
 
References
 
1.  Owen, J. (2010) Wildlife of a garden: a thirty-year study.
 
2.  Smith, R.M, Thompson, K. Warren, P.H. and Gaston, K.J. (2010) Urban domestic gardens (XIII): Composition of the bryophyte and lichen floras, and determinants of species richness. Biological Conservation 143:873–882
 
3.  McClintock, D. (1963) Bryophytes and Fungi  Proc. S. Lond. ent. nat. Hist, Soc  1963 (2)  pp36-38
 
 
Page written by Penny Anderson, compiled by Steve Head
Above: Dilated scalewort Frullania dilatata.  The specimen on the right is rather dry and darker in colour
 
If you look closely at your tree bark you may see purplish little branched leafy liverworts.  Frullania dilatata is one of the commonest, more usually found on ash, willow or poplar in well-lit surroundings and common throughout Britain. You will need a lens – the leaves are only about 1mm wide and 2.3mm long, with rounded lobes and large (for the plant that is) helmet-shaped lobules (small pouches or sacs next to the primary leaf lobe). Underleaves are present too.
 
 
 
References
 
1.  Owen, J. (2010) Wildlife of a garden: a thirty-year study.
 
2.  Smith, R.M, Thompson, K. Warren, P.H. and Gaston, K.J. (2010) Urban domestic gardens (XIII): Composition of the bryophyte and lichen floras, and determinants of species richness. Biological Conservation 143:873–882
 
3.  McClintock, D. (1963) Bryophytes and Fungi  Proc. S. Lond. ent. nat. Hist, Soc  1963 (2)  pp36-38
 
 
Page written by Penny Anderson, compiled by Steve Head
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