Monographs Details: Riccia crassifrons Spruce
Authority: Bischler, Hélène, et al. 2005. Marchantiidae. Fl. Neotrop. Monogr. 97: 1--262. (Published by NYBG Press)
Synonyms:Riccia spruceana Steph.
Description:Species Description - Thalli in gregarious patches; lobes 7-10 mm long, 0.7-1.2 mm wide, rounded or slightly emarginate apically, 3-4 times forked, the basal dichotomy deep, 4-5 mm long; dorsal side light brown or light greenish brown when dry. Median groove shallow, short. Pores 20-40 µm diam., bounded by 4 cells. Ventral scales absent. Cross section of lobes 0.5-0.7 mm high, as wide as high; dorsal edge projecting above the flank as wing with unistratose margin; flanks obliquely ascending, abruptly extending into the wings; ventral edge convex; air chambers in 2 layers; ventral tissue in 2-3 layers. Monoecious (fide Stephani, 1898). Sporangia bulging ventrally. Spores tetrahedral, light brown or red-brown, 55-72 µm diam.; wing vestigial, 1-5 µm wide, or absent; distal face with 6-8 areoles across diam., with thin or slightly thickened ridges and weak tubercles, sometimes with a brown or pale tubercle in the center; proximal face with areoles similar to those of distal face, with tubercles and sometimes a central tubercle, triradiate scar weak.

Discussion:Riccia crassifrons can be distinguished from the other species of subgen. Ricciella by its thallus lobes consisting of dorsal and ventral epidermis bounding 2 layers of air chambers, by the thin lateral thallus wings, and by its spores with a narrow, irregular, and partly vanishing wing.

Distribution and Ecology: Riccia crassifrons is rare and has been recorded only from Venezuela (Barinas; Infante-Sanchez & Heras Perez, 2002), Peru (Loreto) and Brazil (Amazonas). It was collected on acidic silt on river borders.

Distribution:Amazonas Brazil South America| Loreto Peru South America|