Riccia

Silva, José Augusto dos Santos, Fernandes, Rozijane S. & Pinheiro Costa, Denise, 2018, Species diversity of the genus Riccia L. (Marchantiales, Ricciaceae) in Maranhão state, Brazil, Check List 14 (5), pp. 763-769 : 764

Key to the genus Riccia from Maranhão state

1 Plants semiaquatic; thalli forming partial rosettes; spores with 3–5 areolae on the distal face ................. ........................................................... R. stenophylla

1ʹ Plants usually terrestrial; thalli forming rosettes or gregarious patches; spores with more than 5 areolae on the distal face....................................................... 2

2 Scales large (0.05 mm), violaceous, imbricate, reaching beyond the lobe margins ....................... R. vitalii

2ʹ Scales small (0.01–0.02 mm), hyaline, imbricate, not reaching the lobe margins......................................... 3

3 Cells of dorsal tissue without thickened longitudinal strips ............................................ R. planobiconvexa

3ʹ Cells of dorsal tissue thickened or with longitudinal strips ......................................................................... 4

4 Cells of dorsal tissue with thickened walls; thalli margins hyaline; spores subspherical ........ R. mauryana

4ʹ Cells of dorsal tissue with two longitudinal, thickened strips; thalli margins light-green or whitish; spores tetrahedral ............................................. R. weinionis