Monographs Details: Riccia subplana Steph.
Authority: Bischler, Hélène, et al. 2005. Marchantiidae. Fl. Neotrop. Monogr. 97: 1--262. (Published by NYBG Press)
Scientific Name:Riccia subplana Steph.
Description:Species Description - Thalli in complete or partial rosettes, 15-25 mm in diam., or in gregarious patches; lobes 2-3 times forked, 5-15 mm long, 2.5-3.8 mm wide, rounded apically, thin and flattened when dry; dorsal side light green or glaucous, with acute, often slightly ascending margins; flanks and ventral side brown-violaceous. Median groove shallow. Epidermal cells rounded, hyaline, disintegrating except in groove. Ventral scales brown-violaceous, usually not extending beyond lobe margins. Cross section of lobes 2-6 times as wide as high; dorsal edge with thin, ascending wing laterally; flanks oblique; ventral edge nearly flat; dorsal tissue occupying 1/3 of lobe height, of 4 cell layers, cells 40(-55) µm high, walls with narrow, pitted, longitudinal strip. Monoecious. Spores sub-spherical, 85-130 µm diam., violaceous-brown; distal face with 4-6(-8) complete areoles across diam., with thin, high ridges and thin, high tubercles, some connected by a thin, pink-violet membrane; proximal face with similar ornamentation, triradiate scar indistinct. Gametophytic chromosome number n = 8.

Discussion:Riccia subplana is allied to R. plano-biconvexa. The two species are best distinguished by the spores, those of R. subplana being red-violet, with fewer areoles across distal face, and protruding ridges and tubercles on the margins as seen from distal face. A thin, pink-violet membrane connects some of the ridges and gives the spores their particular appearance.

Distribution and Ecology: Riccia subplana is a neotropical species known from Guatemala, Costa Rica, Virgin Islands (St. John), Windward Islands (Guadeloupe (Duss, 1904), La Désirade, Les Saintes, Martinique), Venezuela (Infante-Sanchez & Heras Pérez, 2002), Guyana, French Guiana, Peru (Loreto), and Brazil (Amazonas). It seems infrequent and has been collected on bare soil or rocky, volcanic soil, along streets among paving stones, in gardens, in cultivation, on borders of paths, or shaded under open vegetation, from sea level to 1000 m.

Distribution:Amazonas Brazil South America| Guadeloupe South America| Martinique South America| Loreto Peru South America| Alajuela Costa Rica Central America| Cartago Costa Rica Central America| Guanacaste Costa Rica Central America| San José Costa Rica Central America| Suchitepéquez Guatemala Central America| Cayenne French Guiana South America| Saül French Guiana South America| East Demerara Guyana South America| French Guiana South America| Saint John Virgin Islands of the United States South America| Pointe-à-Pitre Guadeloupe South America|