Riccia boumanii Dirkse, Losada & M.Stech

(Fig. 2)

Journal of Bryology 38 (2): 96 (Dirkse et al. 2016).

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Type: Spain. Prov. de Santa Cruz de Tenerife, La Gomera, La Fortaleza de Chipude, N slopes and plateau, 28°5’47.05”N, 17°17’24.31”W, 1200-1243 m a.s.l., 16.III.1988, G.M. Dirkse (holo-, RIN [RIN-015035]).

SPECIMENS EXAMINED. — China. Gansu, Maqu County, slope near road G345, 33°51’28.14”N, 101°53’28.14”E, 3744 m a.s.l., on soil, C. Shen et al. 20200827-53 (HSNU); Sichuan, Xiaojin County, Siguniang Mountains Nature Reserve, Haizigou, Huahaizi, 31°02’23.66”N, 102°55’52.76”E, 3828 m a.s.l., on soil, R.L. Zhu 20160816-14C (HSNU).

DISTRIBUTION AND HABITAT. — Known from Europe (the Canary Islands) and Asia (China) (Fig. 3). In China, it grows on moist and shady soil, from 3744 m to 3828 m (Fig. 4). The elevation of the populations in China is much higher than that of the type locality, which is from 100 m to 1640 m.

DESCRIPTION

Plants in rosettes, irregular patches or gregarious; terrestrial. Thalli small to medium-sized, 0.8-2.1 mm wide, 5-8 mm long; (1-)2-3-times furcated, shortly to deeply divided. Dorsal surface glabrous, glistening greyish-green when wet, dull, scurfy when dry; median furrow distinct at apex, but immediately become shallow and disappears posteriorly. Dorsal epidermis 2-5-stratose, cells spherical or ovoid, hyaline, in loose cell pillars. Thallus sections of lobes 0.82-1.2 mm high and 1.5-2 times as wide; air chambers absent, but consist of a series of photosynthetic filaments, 8-10 cells high. Storage tissue cells irregularly rounded, thin-walled. Ventral scales prominent, hyaline white, never purplish or violet, wavy, quadrate to hexagonal, mostly going beyond thallus margin, thin-walled. Cilia absent. Rhizoids smooth and pegged. Monoicous. Antheridia scarce, conspicuous near median furrow. Spores tetrahedral, 83-100 µm in diameter, dark brown or blackish; distal surface largely lacunose, low radiating ridges run over distal face, gradually forming small areolae, 3-10 µm in diameter; proximal surface with straight or fragmented trilete mark, distinct, areolae incomplete with papillae or short tubercles at the corners; wing distinct, 7-9 µm wide.