Monographs Details: Riccia brittonii M.Howe
Bischler, Hélène, et al. 2005. Marchantiidae. Fl. Neotrop. Monogr. 97: 1--262. (Published by NYBG Press
Description:Species Description - Thalli in gregarious patches; lobes simple or once forked, 2-5 mm long, 1-2 mm wide; dorsal side light green with narrow, hyaline margins; flanks brownish, or pink-violet, or violet. Median groove deep apically, vanishing toward base of lobes. Epidermal cells disintegrating, basal walls thickened, hypodermal cells with thickened, often yellow-tinged walls. Ventral scales very small, hyaline, not extending beyond lobe margins. Cross section of lobes twice as wide as high; dorsal edge laterally ascending and acute; flanks bordered by a strip of cells with thickened walls, brownish or violet in upper part, below hyaline; ventral edge flat or slightly convex; dorsal tissue in 4 layers. Monoecious. Spores subtetrahedral, 100-140 µm diam., red-brown to dark brown, wingless but sometimes with an incomplete, yellow, narrow and granulose strip on equator; distal face with 6-9 areoles across diam., granulose inside, with thick, dark red or black-red ridges and big tubercles as wide as the ridges; proximal face with areoles of same size than those of distal face, triradiate scar well marked.
Discussion:For the characteristics distinguishing Riccia brittonii from the allied R. breutelii and R. elliottii, see under R. breutelii.Riccia brittonii has a hyaline lobe margin and thickened epidermal and hypodermal cells as in R. sorocarpa. However, the wall thickenings are less conspicuous in R. brittonii, and the spore wall ornamentation is different.
Mayagüez Puerto Rico South America