Didymodon daqingii J. Kou, R.H. Zander

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

7. Didymodon daqingii J. Kou, R.H. Zander & C.

Feng, Ann. Bot. Fenn. 56: 88. 2019. Fig. 13 .

Plants medium-sized, in compact tusts, olivaceous-green or brownish, dull. Stems 1–2 cm long, erect, simple or branched, without hyalodermis, with central strand. Rhizoidal tubers absent. Leaves flexuose when dry, patent to squarrose when wet, from ovate base abruptly narrowed into long lanceolate to subulate acumina, widely canaliculate distally, not decurrent, 2.0–2.9× 0.4–0.5 mm; margins weakly recurved in proximal 1/2–3/4, entire, bistratose in upper third of leaf; costa strong, 75–100 µm wide at leaf base, weakly narrowing upwards, excurrent into a long, fragile, chlorophyllose awn, prominent dorsally, flat ventrally, on both surfaces with quadrate cells, on ventral side smooth or papillose, on dorsal side smooth, in transverse section semicircular, ventral epidermis differentiat- ed, with outer walls not bulging, without band of translucent cells on ventral side below apex, with guide cells in 2–3 layers, ventral stereids absent, dorsal stereids in 1–3 layers, dorsal epidermis differentiated; lamina mainly unistratose, occasionally with bistratose patches in distal third; upper and median laminal cells rounded-quadrate and transversely rhomboidal, with angular lumina, 5–10×4–8 µm, smooth or with low, flat papillae; basal juxtacostal cells rectangular, 17–30×6–10 µm, with moderately thickened, straight walls, basal marginal cells slightly shorter. KOH-reaction yellowish-green. Specialized asexual reproduction absent. Dioicous. Sporophytes unknown.

This species is known from China, Inner Mongolia. We refer to it specimens from Altai and Tyva Republics in southern Siberia and from Suntar-Khayata Mt. Range in Yakutia (see also Discussion on page 137). It was collect- ed on vertical rock outcrops on steppe slope with bushes; on boulders in dry stream bed; on wet, sunny rock outcrops on steep xeric slope; and on rock outcrops on steep forested slope to the flood valley of small river. Didymodon daqingii can be recognized by combination of leaves with long, subulate acumina and long excurrent costae, bistratose leaf margins, occasional bistratose patches in upper leaf lamina, guide cells in 2–3 layers and absence of ventral stereids in transverse sections of costae. Kou et al. (2019) describe its laminal cells as low papillose, but in their illustrations there are no true papillae but cells have slightly bulging and thickened outer walls.

Figures

Fig. 13. Didymodon daqingii (from: Russia, Yakutia, Suntar Khayata Range, Ignatov & Ignatova 15-11, MHA9108739; isolate OK4062). A: habit, dry; B: habit, wet; C: upper laminal cells; D: stem transverse section; E, G: leaf transverse sections; F: mid-leaf cells; H–J: leaves; K: basal leaf cells. Scale bars: 3 mm for B; 2 mm for A; 1 mm for H–J; 100 µm for C–G, K.