Riccia boumanii Dirkse, Losada & M.Stech

Xiang, You-Liang, Ma, Xiao-Ying, Shen, Chao, Lu, Shi-Hui, Huang, Wen-Zhuan, Tian, Gui-Quan & Zhu, Rui-Liang, 2022, The Macaronesian liverwort Riccia boumanii Dirkse, Losada & M. Stech (Marchantiophyta: Ricciaceae) confirmed new to Asia by morphological and molecular evidence, Cryptogamie, Bryologie 20 (14), pp. 201-209 : 204-207

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.

Figures

FIG. 2. — Riccia boumanii Dirkse, Losada & M.Stech: A, habit in the field; B-G, light microscopy micrographs; B-E, transverse section of segments; D, showing the dorsal hyaline epithelial cells; F, proximal face of spore; G, distal face of spore; H, I, SEM micrographs of spores; H, distal face; I, proximal face. All from R.L. Zhu 20160816-14C (HSNU). Scale bars: A, 2 mm; B, C, 500 μm; D, 100 μm; E, 200 μm; F-I, 50 μm.

FIG. 3. — Distribution of Riccia boumanii Dirkse, Losada & M.Stech (red dots), based on data from Dirkse et al. (2016) and this study. The distribution in the Canary Islands is shown in the black rectangle.

FIG. 4. — Habitat of Riccia boumanii Dirkse, Losada & M.Stech in Huahaizi, Haizigou, Siguniang Mountains Nature Reserve, Sichuan, China. The population was found around the lake.