Marchantia polymorpha, sometimes known as thecommon 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 isdioecious, having separate male and female plants.

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 rhizoidswhich 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 containarchegonia, the organs which produce the ova. Male gametophores are topped by a flattened disc containing the antheridia which produce sperm.

(From Wikipedia, February 2015)