Fabronia rostrata Broth., Symb. Sin.

Fabronia rostrata Broth., Symb. Sin. View in CoL 4: 92. 1929.

Type. China: Yunnan, Mekong, 28°11’N, Handel-Mazzetti 8018 (holotype H) .

Illustrations: Figs. 9 View Fig : 11; 10: 9 and 11: 20; see also Dudov et al., 2015.

Plants small, in flat, loose or moderately compact mats, light green or grayish, glossy. Stems 10–15 cm, prostrate, irregularly branched, evenly foliate. Leaves appressed and imbricate when dry, erectopatent to spreading when wet, 0.6–1.0(–1.2) u 0.4–0.5 mm, ovate-lanceolate, gradually narrowed into a long and narrow acumen, slightly concave; margins plane, finely serrulate; costa slender, reaching 0.4–0.6 of leaf length; laminal cells rhomboidal, thin-walled, smooth, 30–60 u 6–10 µm, with length/width ratio 2–4:1 and cell length, µm/ leaf length, mm ratio 19.5–33.7; apical leaf cell to 110 µm long; alar cells differentiated, quadrate, in 3–4 rows at margin. Autoicous. Seta 2–3 mm. Capsule ovoid, 0.6– 0.9 mm long. Operculum almost flat, with rather long oblique beak. Peristome totally reduced. Spores 10–15 µm.

Distribution and ecology. Fabronia rostrata was originally collected in NW Yunnan, at 2325 m a.s.l., on granite rocks in a dry oxbow of Mekong River ( Brotherus, 1929). Gao & Fu (2002) report the species from another locality in Yunnan and from Henan, describing its habitats as “rocks and tree trunks in forests”. In Zabaikalsky Territory the species grew at low elevation, up to 650 m a.s.l., on rock outcrops; in Amurskaya Province it was collected at 400–650 m a.s.l., on rock in the forest and on Tilia amurensis trunk.

Specimens examined: RUSSIA: Zabaikalsky Territory, Nerchinsko-Zavodskiy District, near Nerchinsky Zavod settlement, 658 m alt., 25.VII.2012, Afonina 3912 (LE); Amurskaya Province: Zeisky Disctrict, Zeya Nature Reserve, Tukhuringra range: Gilyiskiy bay of Zeya reservoir, right shore, at 0.3 km to W from cordon “Medvezhiy” 628 m alt., 2.VIII.2013, Dudov & Kotel’nikova# 2013_Br_0021; Izvestkoviy bay of Zeya reservoir, right shore near Izvestkoviy stream estruary 421 m alt., 4.VIII.2013. Dudov & Kotel’nikova 2013_Br_0336 (MW).

Differentiation. In the description of this species V.F. Brotherus (1929) noted such characteristic features of the species as finely serrulate leaf margins and operculum with rather long oblique beak. These characters, as well as the absence of peristome, allow its separation from both F. ciliata and F. pusilla which possess much stronger serrate leaf margins (especially the latter species), mammillate operculum and well-developed, albeit fragile single peristome of 16 teeth, strongly reflexed in dry state and appressed to the urn of opened capsules. Even if partly brocken, teeth remains are apparent enough to indicate peristome presence in these species.