KEY TO RICCIA
Guide to Liverworts of Oregon: RICCIA CONSPECTUS
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1a plants thallose > 2b chloroplasts numerous > 62b thallus tissue complex > 70b terrestrial > 72a epidermal cells uniform > Riccia
Riccia is a notoriously difficult genus which I have yet to understand sufficiently to write a decent key. Most of the species are positively identified only by spore morphology although an experienced expert can recognize them in the field. The most common species is Riccia sorocarpa, a weedy, spring ephemeral often found with the equally weedy Sphaerocarpus texanus. John Wheeler (pers. comm.) reports he has found R. sullivantii in Oregon; it is not included in the key.To skip CONSPECTUS and go directly to KEY TO SPECIES CLICK HERE
CONSPECTUS OF SPECIES
Riccia beyrichiana Hampe ex Lehm. - cilia or spines around margin; antheridial ostioles elevated
Riccia californica Aust. - cilia or spines around margin, antheridial ostioles not elevated
Riccia campbelliana M.A. Howe - no cilia or spines; margin of older part of thallus is orange to reddish brown
Riccia cavernosa Hoffm. - surface of thallus is spongy, whitish; monoicous; distal face of spore alveolate
Riccia crystallinaL.emend Raddi - surface smooth, spongy tissue below, bluish; monoicous; distal face of spore reticulate
Riccia fluitans L. - floating aquatic with thin lobes
Riccia frostii Aust. - similar to Riccia cavernosa but dioicous; distal face of spore vermiculate
Riccia glauca L. - thallus very flat posterior to short apical groove; no cilia or spines
Riccia nigrella DC - very small, with black scales and blackish margins
Riccia sorocarpa Bisch. - small to large, with deep groove throughout; no cilia or spines (but reported in California populations); spores with fine reticulation; most common species of genus
Riccia sullivantii Aust. - looks like a form of Riccia fluitans stranded on mud
Riccia trichocarpa M.A. Howe - long cilia or spines on margins and usually over sporangia