Didymodon changbaiensis J.Kou, C.Feng, H.-X.Xiao & T.-T.Wu, 2023

Wu, Ting-Ting, Feng, Chao, Bian, Tao, Zhang, Guo-Li, Kou, Jin & Xiao, Hong-Xing, 2023, Didymodon changbaiensis (Pottiaceae, Musci), a new species from Changbai Mountain, China and its phylogenetic position based on molecular data, PhytoKeys 221, pp. 147-159 : 147

Didymodon changbaiensis J.Kou, C.Feng, H.-X.Xiao & T.-T.Wu sp. nov.

Figs 3 , 4 Chinese name: 长白山对齿藓

Type.

China. Jilin Province: Changbai Mountain , 42°3'35.316"N, 128°3'51.516"E, on soil over rocks, elevation 1864 m, 2 September 2020, Jin Kou 20200902234 (holotype: NENU!; isotype: NMAC 20200902234!) .

Diagnosis.

It differs from the otherwise similar D. tibeticus in its costa without a ventral costal pad of cells and ventral stereids, transverse section of costa round at mid-leaf and laminal cells with elliptical papillae over the transverse walls between two immediately adjacent cells.

Description.

Plants to 1 cm high, growing in dense turfs, brown-reddish below, green above. Stems erect, frequently branched, in transverse section rounded, central strand weakly differentiated, hyalodermis and sclerodermis absent; axillary hairs filiform, usually 3-4 cells long, with one brown basal cell and hyaline upper ones. Rhizoidal tubers absent. Leaves appressed when dry, erect when moist, ovate or ovate-triangular with a broad base, 0.85-1.3 × 0.43-0.65 mm, channelled ventrally in the upper part; lamina completely unistratose, reddish-orange in KOH; apex acuminate to acute, not cucullate; margins entire, plane, completely unistratose; costa 51.7-86.2 µm wide at base, percurrent to short-excurrent; ventral cells of costa in upper middle part of leaf quadrate or subquadrate, sparsely papillose; dorsal cells of costa in upper middle part of leaf quadrate or subquadrate, sparsely papillose; transverse section of costa round at mid-leaf; with 3-4 guide cells in one layer, absence of ventral stereids, 1-2 layers of dorsal stereids, without hydroids, ventral surface cells bulging, not forming a pad of a single layer of cells, papillose, dorsal surface cells papillose; upper and middle laminal cells subquadrate, hexagonal or shortly rectangular, 5.5-11.1 × 8.9-12.2 µm, dorsally with one low elliptical papilla over the transverse walls which reaches the two immediate cells; basal cells weakly differentiated, smooth, basal juxtacostal cells hexagonal or short-rectangular, 11.1-20 × 5.56-10 µm, evenly thick-walled; basal marginal cells oblate, 5.56-10 × 6.67-10 µm, with regular thickened transverse walls and thin longitudinal walls. Gemmae absent. Dioicous. Sporophyte unknown.

Etymology.

The specific epithet refers to Changbai Mountain, the type locality.

Habitat and distribution.

The new species is currently known only from the type locality at the north slope of Changbai Mountain, Jinlin Province, China, growing on thin soil over rocks.

Figures

Figure 3. Didymodon changbaiensis A dry plants B moist plants C cross-section of stem D axillary hairs E leaves F leaf apex G upper part of costa (dorsal) H upper part of costa (ventral) I upper leaf margin, arrows shows the laminal cells with elliptical papillae over the transverse walls between two immediately adjacent cells. Photographed on 25 May 2022 by Chao Feng from the isotype.

Figure 4. Didymodon changbaiensis A, B median leaf cells, arrows show the laminal cells with elliptical papillae over the transverse walls between two immediately adjacent cells C basal juxtacostal cells D basal marginal cells E-J cross-sections of leaves, sequentially from apex to base. Photographed on 25 May 2022 by Chao Feng from the isotype.