Didymodon hengduanensis J.A. Jiménez, D.G. Long, Shevock & J. Guerra, Phytotaxa

Ignatova, E. A., Fedosov, V. E., Kuznetsova, O. I., Fedorova, A. V. & Ignatov, M. S., 2024, On the genus Didymodon s. str. (Pottiaceae, Bryophyta) in Russia, Arctoa 33 (2), pp. 129-155 : 147-148

6. Didymodon hengduanensis J.A. Jiménez, D.G. Long, Shevock & J. Guerra, Phytotaxa 275(3): 288, 1, 2. 2016. Fig. 12 .

Plants medium-sized to large, in dense tufts, dim green or yellowish green above, brownish below, dull. Stems to 3.5 cm long, erect, simple or branched, without hyalodermis, with central strand. Rhizoidal tubers absent. Leaves appressed and slightly incurved when dry, erectopatent to patent when wet, from ovate base abruptly narrowed into narrow triangular acumina, acuminate, not decurrent, 1.8–2.7× 0.6–0.9 mm, canaliculate distally; margins narrowly recurved at proximal 1/2, unistratose, entire; costa strong, 60–100 mm wide at leaf base, weakly narrowed upwards, percurrent or ending few cells below apex, on dorsal side prominent, on ventral side flat or weakly convex, on both sides with quadrate, smooth cells, without band of translucent cells on ventral side below apex, in transverse section semicircular, with 4–6 guide cells in 1 layer, ventral stereids in 1(2) layers, ventral epidermis differentiated, with not or slightly bulging outer walls, dorsal stereids in 1–2 layers, dorsal epidermis differentiated; lamina unistratose; upper and medi- an laminal cells round-quadrate, elliptic and transversely elliptic, 4–10×5–10 µm, with moderately thickened walls, on both surfaces with 1(2) simple papillae per cell; basal juxtacostal cells short rectangular, rarer quadrate, 8–45×5–10 µm, smooth, with moderately thickened, straight walls, chlorophyllose; basal marginal cells in 8– 10 rows quadrate and transversely rectangular. KOH-reaction yellow. Specialized asexual reproduction absent. Dioicous. Perigonia terminal. Setae 8–10 mm, reddish-brown. Capsules ovate-cylinfric, ca. 2 mm long, brown. Opercula high conic, ca. 1 mm long. Peristome on very low basal membrane, teeth 32, 1100 µm long, spirally twisted, pale reddish, papillose. Spores 14–16 µm.

This species in currently known from few localities in China (Yunnan and Sichuan) and from two localities in Russia: Sedaya Mt. in Primorsky Territory and Slyudyanka River valley in Irkutsk Province. It was collect- ed on rocky soil at roadside and on blocks of marble in a quarry. It can be distinguished from D. validus in having sparsely papillose laminal cells (versus smooth) .

Figures

Fig. 12. Didymodon hengduanensis (A, F–P from: Russia, Primorsky Territory, Sedaya Mt., Ignatov & Ignatova 13-1517, MHA9109153; isolate OK3326; B–D from: Russia, Irkutsk Province, Slyudyanka, Ignatov et al. 18-4492, MW9090873, isolate OK4058). A: habit, wet; B: plant with sporophyte; C: capsule; D: male plant; E: habit, dry; F, J: upper laminal cells; G–I, O: leaves; K: mid-leaf cells; L–N: leaf transverse sections; P: basal leaf cells. Scale bars: 3 mm for A–B, D; 2 mm for C, E; 1 mm for G–I, O; 100 µm for F, J–N, P.