Monographs Details: Riccia viannae Jovet-Ast
Authority: Bischler, Hélène, et al. 2005. Marchantiidae. Fl. Neotrop. Monogr. 97: 1--262. (Published by NYBG Press)
Scientific Name:Riccia viannae Jovet-Ast
Description:Species Description - Thalli in partial rosettes, or in gregarious patches; lobes 2-3 times forked, 5-15 mm long, 2-4 mm wide, rounded or obtuse apically; dorsal side light green grayish with hyaline, inflexed margins when dry, dark green when moist; flanks often with light pink spots. Median groove deep apically, vanishing below. Epidermal cells disintegrating except in groove, spherical; below epidermis 2 layers of hyaline cells, the upper one with thickened walls. Ventral scales hyaline, reaching or extending beyond lobe margins, bordered by cells with thickened walls. Cross section of lobes twice as wide as high apically, 3-4- times as wide as high below; dorsal edge with wings of 1-4 cells laterally; flanks obliquely ascending, then concave; ventral edge convex; cells of dorsal tissue with thin longitudinal strips. Monoecious. Spores 76-120 µm diam., light brown or red-brown, wingless; distal face with 4-6 areoles across diam., granulose inside, the central larger, of 24-30 × 20-25 µm, those of the periphery 15-19 µm diam., vanishing often toward equator and replaced by tubercles or sinuose, thin and low ridges with weak or without tubercles; proximal face with weak ornamentation of low tubercles or granules, or with numerous, nearly indistinct, small areoles, triradiate scar weak or indistinct.

Discussion:Riccia viannae is related to R. lamellosa. However, the spores in the 2 species are quite distinct, those in R. lamellosa being red-brown with black ridges, in R. viannae brown (when mature) and translucent, with granulose areoles.
Distribution:Santa Catarina Brazil South America| Rio Grande do Sul Brazil South America|