Didymodon icmadophilus (Schimp. ex Müll. Hal.) K. Saito, J. Hattori Bot. Lab.

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 : 142-143

3. Didymodon icmadophilus (Schimp. ex Müll. Hal.) K. Saito, J. Hattori Bot. Lab. 39: 519. 1975. — Barbula icmadophila Schimp. ex Müll. Hal., Syn. Musc. Frond. 1: 614. 1849. Fig. 8 .

Plants small to medium-sized, in dense tufts, brownish-green, olivacous-green or brownish, dull. Stems to 3.5 cm long, erect, simple or branched, with central strand. Rhizoidal tubers absent. Leaves erect, appressed when dry, erect-patent to spreading when wet, ovate-lanceolate, lanceolate or ovate-triangular, acuminate, not decurrent, 0.6– 2.2× 0.3–0.6 mm, canaliculate distally; margins narrowly recurved in proximal 1/2, unistratose, entire; costa moderately strong, 30–85 µm wide at base, weakly narrowing upwards, excurrent into long subula to 0.25 of leaf length, weakly prominent dorsally, on ventral side flat or weakly convex, on both surfaces with quadrate cells, smooth on ventral surface, smooth or papillose on dorsal surface, without band of translucent cells on ventral side below apex, in transverse section semicircular, with 3–5 guide cells in 1 layer, ventral stereids in (0)1–2 layers, ventral epidermis differentiated, with outer walls not bulging, dorsal stereids in 2–3 layers, dorsal epidermis differentiated; lamina unistratose; upper and median laminal cells rounded-quadrate, elliptic and transversely elliptic, 5–13×5–13 µm, with moderately thickened walls, papillose, with papillae mainly on dorsal surface, occasionally also with few papillae on ventral surface, simple or bifurcate, occasionally low; basal juxtacostal cells rectangular and quadrate, 8– 40×5–13 µm, smooth, with moderately thickened walls, chlorophyllose; basal marginal cells not differentiated or slightly shorter. KOH-reaction yellowish or orange. Specialized asexual reproduction absent. Dioicous, sporophytes rare, in the territory of Russia unknown.

This species was recorded from many areas in Russia, but most these records were erroneous, based on specimens actually belonging to other species, mainly D. validus , sometimes D. daqingii or described here D. abramovae . Here we confirm the identity of one specimen of D. icmadophilus from the Caucasus, Karachevo-Cherkessian Republic, Teberdinsky Nature Park, where it was collected on wet rocky soil near waterfall. Leaves with long-excurrent costae are also characteristic for D. daqingii and described here D. abramovae . First of these species can be separated by bistratose leaf margins and costae with two layers of guide cells and no ventral stereids; leaves of D. abramovae are more gradually tapered from ovate base and possess smooth laminal cells.

Figures

Fig. 8. Didymodon icmadophilus (from Russia, Caucasus, Karachaevo-Cherkessian Republic, Teberdinsky Nature Park, Ignatov & Ignatova 05-3531, MW9035941, isolate OK4057). A: habit, dry; B: habit, wet; C–F: leaf transverse sections; G: mid-leaf cells; H–K: leaves; L: stem transverse section; M: basal leaf cells; N: upper leaf cells. Scale bars: 2 mm for B; 1 mm for A; 0.5 mm for H–K; 100 µm for C–G, L–N.