Riccia boumanii

(Fig. 2) Journal of Bryology 38 (2): 96 (Dirkse et al. 2016). — 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 G 345, 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 - 14 C (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. 40 ° W 20 ° W 0 ° 20 ° E 40 ° E 60 ° E 80 ° E 100 ° E 120 ° E 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.