Didymodon mongolicus D.P. Zhao & T.R. Zhang

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 : 148-149

8. Didymodon mongolicus D.P. Zhao & T.R. Zhang ,

Bangladesh J. Pl.Taxon. 23(2): 175. 2016. Fig. 14 .

Plants small, in dense tufts, brownish-green or brown, dull. Stems to 3 cm long, erect, simple or branched, without hyalodermis, with central strand. Rhizoidal tubers absent. Leaves erect and appressed when dry, erectopatent when wet, ovate to ovate-lanceolate, with wide bases and short acumina, narrowly acute, not decurrent, 0.5–1.3 × 0.25–0.5 mm, canaliculate distally; margins narrowly recurved in proximal 1/2–2/3, unistratose, entire; costa 25–60 µm wide at leaf base, weakly narrowing upwards, percurrent, prominent dorsally, flat or slighly concave ventrally, on both surfaces with quadrate, smooth or papillose cells, without band of translucent cells on ventral side below apex, in transverse section semicircular or almost circular, with 3–5 guide cells in 1 layer, ventral stereids in 0–1 layers, ventral epidermis differentiated, with flat or slightly bulging outer walls, dorsal stereids or substereids in (0)1–2 layers, dorsal epidermis differentiated; lamina unistratose; upper and median laminal cells rounded-quadrate, short rectangular and transversely rectangular, 7–11×7–10 µm, with moderately thickened walls, smooth on both surfaces or on dorsal surface with 1–2 simple papillae per cell; basal juxtacostal cells short rectangular and quadrate, 13–30×7–9 µm, with moderately thickened, straight walls, smooth, chlorophyllose; basal marginal cells in 8–9 rows quadrate and transversely rectangular. KOH-reaction yellowish or orange. Specialized asexual reproduction absent. Dioicous. Perigonia not seen. Perichetia terminal. Sporophytes unknown.

Didymodon mongolicus is known from China (Inner Mongolia) and Mongolia; in the present study its presence in southern Siberia, Yakutia, and Dagestan is confirmed. Its Chinese and Mongolian plants have leaves with smooth cells, whereas in populations from Russia plants both with smooth and papillose on dorsal surface cells were revealed. Plants with papillose on dorsal suface leaf cells resemble D. tibeticus and D. icmadophilus . However, D. tibeticus is a smaller plant with leaves to 0.45 mm long, having flat margins, and D. icmadophilus has wider leaf bases and long excurrent costae.

Figures

Fig. 14. Didymodon mongolicus (from: Russia, Yakutia, Ust-Nera, Ignatov & Ignatova 5-1508, MHA9109166; isolate OK3327). A: habit, dry; B: habit, wet; C–E: leaf transverse sections; F: mid-leaf cells; G: upper laminal cells; H–K: leaves; L: basal leaf cells. Scale bars: 2 mm for A–B; 0.5 mm for H–K; 100 µm for C–G, L.