Marchantia polymorpha subsp. polymorpha

A large, dioicous thallose liverwort that form thick forked, prostrate mats. The upper surface has a network of lines and cup shaped resceptacles that contain gemmae. Marchantia polymorpha occurs as 3 subspecies in Britain. Marchantia polymorpha subs. polymorpha has a broad black midrib which is usually quite prominent and distinctive. It is found in more natural habitats than Marchantia polymorpha subsp. ruderalis such as on rocks and stones besides streams and rivers. It has a scattered distribution in Britain and is frequent but local in south Wales. Most records in West Glamorgan are from the banks of streams in the uplands of Neath Port Talbot. All subspecies produce sexual structures in receptacles. Male plants produce flat topped receptacles on stalks with rounded lobes along their margin. The female receptacles are also produced on stalks, but they have distinctive, finger-like lobes (see photos of Marchantia polymorpha subsp. ruderalis).

Marchantia polymorpha subsp. montivagans has been recorded in southeast Wales but not in West Glamorgan.