Guide to Liverworts of Oregon: Marchantia quadrata Scop.
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1a plants thallose > 2b chloroplasts numerous > 62b thallus tissue complex > 70b terrestrial > 72b pores differentiated > 73b gemmae absent > 75b trigones small or absent > 77b pores not stellate > 79a pores compound > 80b scale appendage narrow > Preissia quadrata
Synonyms: Preissia quadrata (Scop.) Nees
Special Status: ORBIC List 2.
Recognition: This species has compound pores, the only genus besides Marchantia with this kind of pore. It differs in having narrow, pointed ventral scale appendages; in Marchantia the appendages are cordate.
Distribution: Grows on soil. Found along the Sandy River in Multnomah County; Mount Jefferson Wilderness, Deschutes County (Scot Loring 5503); and in the mountains of Baker and Wallowa County.
Comments: A recent (2007) visit to the Sandy River site failed to turn up this species. It was seen there as recently as 1990 (DHW 4200).
Stotler and Crandall-Stotler (2017) first accepted the proposal of Grolle and Long (2000) to transfer Preissia back to Marchantia. This synonymy was further bolstered by papers on Marchantiaceae by Forrest, et al. (2006) and Long, et al. (2016). The latter paper erected subgenus Pressia Corda to indicate its isolation from other subgenera in Marchantia.
Little of the recent liverwort literature with which I'm familiar, including all major identification manuals used in my work, recognize this synonymy. Although the spores of Marchantia quadrata are very large and different from the tiny spores of Marchantia polymorpha, the barrel shaped spores and both male and female receptacles are stalked demonstrate their relationship.
Marchantia quadrata - Left: Elkhorn Ridge, Baker Co, Oregon. Right: North Cascades National Park, WA. M. Hutten.
Side view of thallus. North Cascades National Park, WA. M. Hutten.
Left: looking down on pores in epidermis; right: looking at bottom of pore apparatus (epidermis shaving placed upside down on slide). - North Cascades National Park, WA. M. Hutten.
Stained cross section showing pores and air chambers. - North Cascades National Park, WA. M. Hutten.
Thallus cross section (lightly stained with toluidine blue). - North Cascades National Park, WA. M. Hutten.
Spores and elaters. Pend Orielle County, Washington. Beck 2428.
Spores and elaters. Pend Orielle County, Washington. Beck 2428.
Distal aspect. Calif., Tulare Co., Sequoia Natl. Park, Mineral King, trail to Franklin Lakes. Doyle 7849 (UC).
Proximal aspect. Calif., Tulare Co., Sequoia Natl. Park, Mineral King, trail to Franklin Lakes. Doyle 7849 (UC).
Lateral aspect. Calif., Tulare Co., Sequoia Natl. Park, Mineral King, trail to Franklin Lakes. Doyle 7849 (UC).