Bryophytes of Santa Barbara

Marchantia polymorpha L.

Marchantia polymorpha is a large complex thallose liverwort with distinctive circular gemmae cups with a fringed margin, containing disc-shaped gemmae (asexual propagules capable of developing into new, genetically identical plants). Thalli come in a variety of shades of green, are 5-10 mm wide and up to 10 cm long, and often have a dark line down the center (midrib), along which the gemmae cups are situated. The upper surface is dotted with complex pores and polygonal reticulations. The species is dioicous, with separate male and female plants, males with stalked antheridiophores with circular tops, and females with stalked archegoniophores with carpocephela with 7-11 long narrow lobes.
Scroll down for photos with labeled parts and more detailed descriptions.
Marchantia polymorpha
Marchantia polymorpha CC BY-NC Amanda Heinrich
Marchantia polymorpha is the poster-child of liverworts, appearing in text books across the globe. It does not appear to be common in the wild in Santa Barbara County, so I have included only a few photos of asexual plants, but more information is readily information on the web.
Detailed Descriptions with Photos (click to enlarge)

Marchantia polymorpha has distinctive circular gemmae cups with a fringed margin on the upper surface of the wide thallus, typically along the midrib. Gemmae cups contain disc-shaped gemmae which are asexual propagules capable of developing into new, genetically identical plants.

Circular gemmae cups are diagnostic for the genus Marchantia.

Marchantia polymorpha
Marchantia polymorpha with circular gemmae cups. CC BY-NC Amanda Heinrich

The dorsal surface of Marchantia polymorpha may have a dark line along the midrib, which may be continuous or interrupted, strong or weak.

Marchantia polymorpha
Marchantia polymorpha with dark line along midrib. CC BY-NC Amanda Heinrich
Habitat and Distribution

Marchantia polymorpha has a nearly worldwide distribution, and is often found in greenhouses and gardens, as well as on soil and on rock near creeks, rivers, and seeps.

Thus far, I have seen Marchantia polymorpha at only one location in the wild in Santa Barbara County, in the creek below Tangerine Falls in Cold Spring Canyon.

Map generated by google maps using data from the Consortium of Bryophyte Herbaria of accessioned collections from herbaria.

Marchantia polymorpha distribution
Name: The genus, Marchantia, is named for Nicholas Marchant, a French botanist from the seventeeth century. The specific epithet, polymorpha, refers to the many (poly = Greek for many) forms (morph = Greek for form, shape) of this worldwide species.
Similar Species in Santa Barbara County: Marchantia is the only genus with circular gemmae cups, and M. polymorpha is the only species recognized in the state of California. There are, however, many other species of Marchantia elsewhere in North America and around the world.
References and Further Reading
Contributions toward a bryoflora of California III. Keys and annotated species catalogue for liverworts and hornworts, William T. Doyle and Raymond E. Stotler, Madroño, A West American Journal of Botany, Volume 53, Number 2. This issue can be ordered here here.