Marchantia polymorpha

Marchantia polymorpha
Scientific classification
Kingdom:	Plantae
Division:	Marchantiophyta
Class:	Marchantiopsida
Order:	Marchantiales
Family:	Marchantiaceae
Genus:	Marchantia
Species:	M. polymorpha
Binomial name
Marchantia polymorpha L.
Synonyms
Marchantia alpestris Marchantia aquatica

Marchantia polymorpha, sometimes known as the common liverwort or umbrella liverwort, is a large liverwort with a wide distribution around the world. It is variable in appearance and has several subspecies. It is dioecious, having separate male and female plants.

Description

It is a thallose liverwort which forms a rosette of flattened thalli with forked branches. The thalli grow up to 10 cm long with a width of up to 2 cm. It is usually green in colour but older plants can become brown or purplish. The upper surface has a pattern of hexagonal markings. The underside is covered by many root-like rhizoids which attach the plant to the soil. The plants produce umbrella-like reproductive structures known as gametophores. The gametophores of female plants consist of a stalk with star-like rays at the top. These contain archegonia, the organs which produce the ova. Male gametophores are topped by a flattened disc containing the antheridia which produce sperm.

Reproduction

Marchantia polymorpha can reproduce both sexually and asexually. Sexual reproduction involves sperm from the male plant fertilizing ova from the female plants. A fertilized ovum develops into a small sporophyte plant which remains attached to the larger gametophyte plant. The sporophyte produces male and female spores which develop into free-living gametophyte plants.

Asexual reproduction can occur when older parts of the plant die and newer branches develop into separate plants. It can also occur by means of gemmae, balls of cells which are genetically identical to the parent and contained in cup-like structures on the upper surface of the plant. These are dispersed when rain splashes the cups and develop into new plants.

Distribution and habitat

It is found worldwide from tropical to arctic climates. It grows on moist soil and rocks in damp habitats such as the banks of streams and pools, bogs, fens and dune slacks. It rapidly colonizes burnt ground after fires. It often grows in man-made habitats such as gardens, paths and greenhouses and can be a horticultural weed.

References

• Altland, James. Marchantia polymorpha. Accessed 4 July 2009.
• British Bryological Society (2008) Marchantia polymorpha. Accessed 4 July 2009.
• Matthews, Robin F. (1993) Marchantia polymorpha. Accessed 4 July 2009.
• Raven, Peter H.; Ray F. Evert & Susan E. Eichhorn (1999) Biology of Plants, W. H. Freeman, New York.
• Rook, Earl J. S. (1999) Marchantia polymorpha. Accessed 4 July 2009.
• Smith, AJE (1989) The Liverworts of Britain and Ireland, Cambridge University Press, Cambridge.

External links

• Photos of Marchantia polymorpha