Mannia gradsteinii, Xiang & Zhu, 2023

Xiang, You-Liang & Zhu, Rui-Liang, 2023, Morphological and molecular evidence for a new species, Mannia gradsteinii sp. nov. (Aytoniaceae) from southwestern China, Cryptogamie, Bryologie 44 (12), pp. 237-245 : 239

Mannia gradsteinii sp. nov.

( Figs 2-4 )

Similar to Mannia triandra (Scop.) Grolle but differing in larger epidermal pores (72)136-204 µm in diameter, smaller spores 47-57 µm, 3-6 areolae across the spore distal surface, air chambers with 2-4 layers and ventral scales not reaching beyond thallus edge.

HOLOTYPE. — China. Yunan, Weixi County, Tacheng Town, near Duonage Village , 27°20’39.40”N, 99°19’01.22”E, 2270 m, on soil, 28.IV.2017, Y.L. Xiang & P.F.Wang 20170428-12 (holo-, HSNU!).

ADDITIONAL SPECIMEN EXAMINED. — China. Yunnan, Weixi County, Biluoxueshan, 28°08’18.59”N, 98°47’48.26”E, 3084 m, on soil, 28.IV.2017, Y.L. Xiang & P.F. Wang 20170428-3 ( HSNU) .

ETYMOLOGY. — Mannia gradsteinii sp. nov. is named in honor of the remarkable bryologist, Prof. Stephan Robbert Gradstein on the occasion of his 80 th birthday.

ECOLOGY AND DISTRIBUTION. — Mannia gradsteinii sp. nov. occurs at altitudes of 2270-3084 m, growing on soil or on rock with a thin layer of soil under shrubs. Until now, it is known only from Weixi County, northwestern Yunnan, China.

DESCRIPTION

Plants thalloid, light green on dorsal surface, thin and delicate, sub-dichotomously branched, lobes 8-19 mm long, 2.8-4.6 mm wide; dorsal surface flat to slightly concave, with faint reticulation mark due to the underlying chamber walls; margins thin, not crenate; dorsal epidermal cells of thallus, 24-71×22-42 µm, thin-walled, trigones often absent; oil-cells scattered in epidermis, yellowish-brown; epidermal pores simple, (72)136-204 µm in diameter, surrounded by 2-3 concentric rings, each formed by 6-9 cells, cells thin-walled, radial walls not thickened; assimilatory tissue loose, with large air chambers in 2-4 layers, occupying c. 2/3-3/4 of the thallus height in the middle and completely filling the wings, without photosynthetic filaments, seldom with inconspicuous yellowish brown oil bodies in assimilation and storage tissue; rhizoids of two kinds: smooth and pegged; ventral scales in two rows, not reaching beyond thallus edge, hyaline to pale purplish, semicircular to oblong semicircular or triangular, marginal slime-papillae one-celled, hyaline, abundant, oil cells numerous; appendages 1(-2) per scale, subulate, acuminate, purplish; appendage 324-441 µm long and 73-193 µm wide, without oil cells or sometimes with a single oil cell.

Monoicous. Archegoniophore arising from apices of main branches; androecia close to archegoniophore bases; androecia sessile, usually several, slightly upraised in poorly defined slightly raised rounded clusters or depressions; female receptacles hemispherical, without pseudoperianth, 4.6-8.2 mm in diameter; receptacle usually bearing four sporophytes; stalk 8.1-12.3 mm long, 0.4-0.6 mm in diameter, with single rhizoidal furrow; spores yellow to brown, 47-57 µm in diameter (SEM), trilete, with similar sculpturing on proximal and distal surfaces, 3-6 areolae across the spore distal surface and with middle depression on spore proximal face; proximal surface incompletely areolate; proximal disc absent; equatorial apertures rather inconspicuous, usually three; equatorial rim inconspicuous; elaters yellowish brownish, 359-560 µm long, 8.7-11 µm broad at middle, 2-3-spiral.

Figures

FIG. 2. — Mannia gradsteinii sp. nov.: A, habit in the field; B, dorsal surface of thallus; C, D, female receptacle, dorsal and ventral view respectively; E-H, SEM micrographs of spores; E, F, distal view; G, proximal view; H, side view.All from Y.L. Xiang & P.F. Wang 20170428-12 (holo-,HSNU).Scale bars:A, 1 cm; B, 2 mm; C, D, 5 mm; E-H, 20 μm.

FIG. 3. — Mannia gradsteinii sp. nov.: A, C, D, transverse section of segments; B, epidermal pores; E, F, ventral scales with appendages. All from Y.L. Xiang & P.F. Wang 20170428-12 (holo-, HSNU). Scale bars: A, E, F, 250 μm; B-D, 200 μm.

FIG. 4. — Mannia gradsteinii sp. nov.: A, B, light microscopy micrographs of spores; A, distal view; B, proximal view; C, elater; D, capsule wall; E, F, transverse section of archegoniophore stalks. All from Y.L. Xiang & P.F. Wang 20170428-12 (holo-, HSNU). Scale bars: A-D, 50 μm; E, F, 200 μm.