Monographs Details: Riccia breutelii Hampe ex Steph.
Authority: Bischler, Hélène, et al. 2005. Marchantiidae. Fl. Neotrop. Monogr. 97: 1--262. (Published by NYBG Press)
Synonyms:Riccia gaumeri Underw. ex M.Howe
Description:Species Description - Thalli in gregarious patches; lobes 2-3 times forked, 5-10 mm long, 1-2.2 mm wide, thin and flattened, rounded and slightly emarginate apically; dorsal side light brown or brownish when dry, with narrow, hyaline, slightly undulate margins; flanks and ventral side pale. Median groove deep apically, vanishing below. Epidermal cells disintegrating. Ventral scales short, hyaline. Cross section of lobes 0.3-0.4 mm high, 2-5 times as wide as high; dorsal edge acute laterally, ending in a wing with 2-3 hyaline cells apically; flanks obliquely ascending, becoming horizontal in the wings; ventral edge convex; dorsal tissue in 2-4 cell layers, cells identical to those of ventral tissue. Dioecious? Spores subtetrahedral, 100-140 µm diam., red-brown or dark brown, wingless or with incomplete, narrow, yellow strip on equator; distal face with 6-7 areoles across diam, in the smallest spores, with 7-10 in the largest spores, with thick, dark red or nearly black ridges and big tubercles; proximal face with similar or smaller areoles and narrower ridges, 20-25 per facet, triradiate scar weak.

Discussion:The Brazilian specimen has spores with 4-7 areoles only across diam, of distal face. Riccia breutelii, R. brittonii, and R. elliottii are sometimes considered to be synonyms (Howe, 1923). Several characteristics keep the 3 species apart, however. In R. elliottii, the spores are relatively small (80-90 µm diam.) and the proximal face has only 4-5 areoles per facet. In R. brittonii, the epidermal cells have thickened walls and the flanks of the lobes show a violaceous strip of cells with thickened walls.
Distribution:Pará Brazil South America| Jalisco Mexico North America| Yucatán Mexico North America| Loreto Peru South America| Guanacaste Costa Rica Central America| Junín Peru South America| Falcón Venezuela South America| Saint Kitts Saint Kitts and Nevis South America|