Cyathodium cavernarum Kunze

Cyathodium cavernarum Kunze View in CoL

Figure 3A–E

Material examined. BRAZIL – Maranhão • Carolina, Parque Nacional Chapada das Mesas, Cachoeira São Romão ; 07°04′25″S, 047°05′26″W; alt. 256 m; 07 Jun. 2018; J. A. S Silva 275 col.; CCAA 1587 GoogleMaps . • ibid., Com- plexo Pedra Caída, cachoeira do Santuário ; 07°02′44″S, 047°27′01″W; alt. 128 m; 07 Feb. 2020; J. A. S Silva 551 col.; CCAA 2696 GoogleMaps .

Identification. Plants rupicolous. Thallus obcuneate, very thin, only 2 or 3 cells wide, with smooth rhizoids, bright green to yellowish, 4–6 × 0.6–1.0 mm, without central midrib; main axis broad and flat; dorsal surface of chlorophyllose thallus with epidermal pores with a ring of 6–8 cells; thallus in cross section with one layer of air chambers without chlorophyllose filaments; ven- tral surface with chlorophyllose cells; margin entire, greenish; ventral scales reduced or absent. Sporophyte on the ventral surface of the thallus (near the apex); involucre sac-shaped; capsule ovoid, dark brown, opening with an operculum; spores spherical and densely spinose, dark brown; elaters long.

Cyathodium cavernarum differs from other spe- cies of thallose liverworts in the study area by having a bright green thallus with few layers of cells, and a sporophyte capsule opening through a ring of cells. It differs

from other species of Cyathodium by having the rhizoids with smooth walls, a sporophyte with an operculum, and spiny spores (Bischler-Causse et al. 2005).

Distribution and ecology. Worldwide (Bischler-Causse et al. 2005 and Söderström et al. 2020). Atlantic Forest ( Minas Gerais), Caatinga ( Bahia, Ceará, Paraíba, Pernambuco, and Piauí), Brazilian Cerrado ( Goiás, Mato Grosso, Maranhão, and São Paulo), Pantanal ( Mato Grosso do Sul) ( Söderström et al. 2020; Flora do Brasil 2020; new data). We collected C. cavernarum on shaded rocks with a thin trickle of water running over the gametophyte. It was collected fertile only at the end of the rainy season.

Lepidoziaceae