Guide to Liverworts of Oregon: Bazzania ambigua (Lindenb.) Trev.
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1b plants leafy > 3b leaves not divided, not ciliate > 6a oil bodies 2+ or unknown > 7b no small dorsal lobe > 10b leaves incubous > 20b lobule absent > 23b lobule absent > 24b leaves 2-3 dentate > Bazzania 1b caducous leaves present > Bazzania 2a oil bodies 2-4 > Bazzania ambigua
Synonym: None.
Special status: Status undetermined because of confusion with B. denudata.
Recognition: Brownish green to pure green; caducous leaves evident; oil bodies 2-4 (7) per cell, spherical to fusiform, clear but not homogeneous and glistening like B. denudata and B. tricrenata, as if composed of indistinct, translucent lumps; lateral margins of the underleaves smoothly curved, not sinuose or irregular; cells of stem epidermis more-or-less quadrate.
Distribution: On bark of trees or on logs; endemic (apparently) to coastal areas of the Pacific Northwest, not reported from in California.
Comments: This is a critical taxon which Schofield (1968, 2002) and Godfrey (1977) have considered conspecific with B.denudata. I believe that much of the problems revolve around placing too much emphasis on variable morphological characters, particularly on the number of teeth. Bazzania denudata supposedly has a preponderance of leaves with three teeth while B. ambigua is supposed to have mostly bidentate leaf tips. Unfortunately, the leaf tip dentition is not a reliable diagnostic character because B. denudata has some shoots with mostly bidentate tips. Comparative study of a mixed population found in Alaska showed clearly these are distinct species, although characters separating them are somewhat subtle. Oil body number has proven to be the most reliable distinguishing character, also the nature of oil bodies helps, indistinctly translucent in B. ambigua versus clear and glistening in B. denudata. Hong (Evansia 6:33-51, 1989) points out, in addition to oil body number, underleaf margin, underleaf lobing, color, and stem cell characters. Despite what he says, however, sinuosity of underleaf margins, the underleaf lobing and brownish color are not consistent enough to be useful. The stem cells quadrate or not is difficult to determine but may prove to be useful when working with dried herbarium specimens.
Bazzania ambigua, Silver Falls, Marion Co., Oregon. DHW 2358
Bazzania ambigua, Cedar River, King Co., Washington. DHW m1979
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