Guide to Liverworts of Oregon: Marchantia polymorpha L.
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Synonym: Marchantia aquatica (Nees) Burgeff (Schuster 1992b); Marchantia polymorpha subsp. polymorpha (Paton 2000).
Special Status: None.
Recognition: Of the three species of Marchantia treated here, this is the most distinctive in its entire ventral scale appendages and thallus with a dark central stripe down its upper surface.
Distribution: Near streams, usually on mineral substrates; widespread in western Oregon, from low elevations up to 5500'/1675m. Not likely to be found in urban habitats.
Comments: In the past, M. polymorpha has generally been used in a broad sense, to include all three species recognized in this treatment. When used in a restricted sense, it must be used for the taxon Schuster (1992b) (and I) called M. aquatica. It is unfortunate that M. aquatica is not the valid name for this taxon, that what Schuster called M. aquatica appears to be a synonym of M. polymorpha L. in the strict sense. What we would prefer to call M. aquatica could be called M. latifolia according to Damsholt (2002) because he thought it was a separate species from M. polymorpha s.s. as well as M. alpestris.
Marchantia polymorpha - Jackson County, Oregon. DHW 9957a.