Monographs Details: Riccia frostii Austin
Authority: Bischler, Hélène, et al. 2005. Marchantiidae. Fl. Neotrop. Monogr. 97: 1--262. (Published by NYBG Press)
Family:Ricciaceae
Scientific Name:Riccia frostii Austin
Description:Species Description - Female thalli larger than male, in complete or incomplete rosettes, spongy, to 10 mm diam., with crowded lobes partially creeping over each other; lobes 1-1.4 mm long, l-1.3(-2) mm wide, rounded or truncate apically, 2-4 times forked, segments to 2 mm long; dorsal side green, or bluish green, or with pink spots on margins. Male thalli 0.3-1.5 mm diam., spongy, rounded or with 2-4 lobes, often crossshaped, pink on borders or over the whole dorsal side. Median groove short or absent. Pores small in younger parts, larger in older. Ventral scales absent. Cross section of lobes 0.3-0.5 mm high, 3-6 times as wide as high; dorsal edge obtuse laterally; flanks obliquely ascending; ventral edge hardly convex; air chambers 2/3-3/4 of lobe height, in 1-2 layers; ventral tissue of large cells. Dioecious. Archegonia deeply immersed, necks white or violet, protruding. Antheridial necks protruding, often purplish. Sporangia usually numerous, black, bulging mainly ventrally. Spores red-brown or yellow-brown, 40-65 µm diam.; wing narrow, 2-3 µm wide, punctate-vermiculate; distal face with irregular, branched, vermiculate ridges radiating from distal pole; proximal face with vermiculate ridges, often absent near proximal pole, triradiate scar of thin ridges. Gametophytic chromosome number n = 8.

Discussion:Riccia frostii can be distinguished from the other species of subgen. Ricciella by its spore ornamentation, with wormlike, thin ridges radiating from the distal pole.
Distribution:Neuquén Argentina South America| Rio Negro Argentina South America| Montevideo Uruguay South America|