Riccia stenophylla Spruce, 1889

Fernandes, Rozijane Santos, Silva, José Augusto dos Santos, Ottoni, Felipe Polivanov & Pinheiro Costa, Denise, 2021, Diversity of thalloid liverworts in Brazilian Savanna of Parque Nacional da Chapada das Mesas, Maranhão, Brazil, Check List 17 (1), pp. 45-58 : 54

Riccia stenophylla Spruce

Figure 7A–E

Material examined. BRAZIL – Maranhão • Carolina, Parque Nacional Chapada das Mesas, Cachoeira do Prata ; 06°59′41″S, 047°09′53″W; alt. 197 m; 29 Oct. 2017; J. A. S. Silva 146 col.; CCAA 1533 . • ibid.; J. A. S. Silva 202 col.; CCAA 1578 . • ibid.; J. A. S. Silva 229 col.; CCAA 1551 .

Identification. Plants terrestrial or semiaquatic. Thallus bright green, dichotomous, 2–8 × 0.2–0.4 mm, linear, without central midrib; dorsal surface with or without a slight median groove with photosynthetic cells, with pores bounded by four or five cells; air chambers in one or two layers; ventral surface greenish; margin entire, green to hyaline; ventral scales hyaline, 0.01 mm long. Sporophytes immersed in the thallus, forming a bulge ventrally, without involucre; capsule spherical, brown; spores tetrahedral, brown to yellow, without elaters.

Riccia stenophylla is a terrestrial or semiaquatic plant, with a long and slender thallus, smooth median

area with or without a groove, and sporophyte forming a bulge ventrally. Riccia stenophylla is sometimes misidentified as R. fluitans L. since these species are both semiaquatic and have a thin stem and internal sporophyte forming a ventral bulge in the thallus. However, R. fluitans has a Holarctic distribution ( Gradstein and Costa 2003; Stotler and Crandall-Stotler 2017), while R. stenophylla is a Neotropical species ( Gradstein et al. 2016).

Distribution and ecology. Tropical and subtropical America ( Argentina, Brazil, Colombia, Costa Rica, United States, Guatemala, Mexico, Nicaragua, Panama, Paraguay, Peru, and Uruguay) (Bischler-Causse et al. 2005; Gradstein et al. 2016; GBIF.org 2020). Brazilian biomes and states: Atlantic Forest (Espírito Santo, Paraná, Rio de Janeiro, Santa Catarina, and São Paulo), Caatinga (Bahia, Ceará, Paraíba, and Pernambuco), Cerrado (Goiás, Maranhão, and Mato Grosso), Pantanal (Mato Grosso do Sul), and Pampas (Rio Grande do Sul) ( Flora do Brasil 2020). We found this species only at the end of the rainy season in ravines near rivers and streams in open habitats which were partially exposed to the sun.