Tortella fleischeri (E. Bauer) J.J. Amann, Beitr. Kryptogamenfl.

Tortella fleischeri (E. Bauer) J.J. Amann, Beitr. Kryptogamenfl. View in CoL Schweiz 7(2): 30. 1933. – Trichostomum fleischeri E. Bauer, Musci Eur. Exsic. 15: no. 741. 1910. Fig. 5 View Fig , 6E, J View Fig .

Plants small to medium-sized, in dense, easily separated tufts, light-green, yellowish-green or rusty-brownish. Stems to 6 cm long, irregularly branched, densely foliate, weakly tomentose, round or triangular in transverse section, with distinct or weak central strand. Leaves 2.0–5.0(–7.0)×0.5–1.0 mm, lanceolate or linear-lanceolate, with length:width ratio 4–7:1, twisted around their axis or contorted when dry, erect-spreading to recurved when wet, occasionally secund, sigmoid, limbs gradually narrowed distally, narrow acuminate at apex, not cucullate, keeled above; leaf bases quadrate, moderately widened; margins plane in mid-leaf, widely incurved above, entire, wavy; costa strong, 60–140 µm wide at base, gradually narrowing distally, with elongate, smooth cells on ventral surface at least in midleaf, on dorsal surface with elongate, not papillose cells, with few spinulae, excurrent into long, sharply dentate mucro, in transverse section in 1 layer of guide cells, 2 stereid bands, with narrow band of undifferentiated ventral epidermis in the centre, dorsal epidermis not differentiated; lamina unistratose; upper and median laminal cells rounded-quadrate, 8–12 µm wide, thick-walled, densely papillose, papillae massive, not obscuring cell walls; basal laminal cells elongate-rectangular, moderately thick- or thin-walled, smooth, hyaline or yellowish; transition between basal and limb cells abrupt, V-shaped, or more or less gradual, U-shaped. Dioicous, sporophytes very rare, in the territory of Russia unknown.

Distribution and ecology. This species was described from Austria. Köckinger & Hedenäs (2023) characterize it as calciphilous and cryophilous species, usually growing above tree line. Outside the Alps, they report it from Slovakia, Montenegro, and Scotland, considering its presence in the latter locality as surprising, as it is usually substituted in the north of Europe by ecologically similar T. cuspidatissima and T. spitzbergensis . Nevertheless, in Russia it was discovered in the northeastern European part, where T. cuspidatissima was not found and T. spitzbergensis was recorded only on Novaya Zemlya. Tortella fleischeri was identified in collections from Nenetz Autonomous district, on Yugorsky Peninsula and Vaigach Island. It was also revealed in collections from Novaya Zemlya (belongs to Arkhangelsk Province) and Yamalo-Nenets Autonomous District in the north of West Siberia.

According to the label data, Tortella fleischeri grew on gravely substrate in different types of tundra.

Differentiation. Specimens from Russia were stored in herbaria under the names T. tortuosa and T. cf. arctica . From both these species T. fleischeri differs by presence of stem central strand (however, sometimes indistinct) and narrow strip of smooth cells along ventral surface of costa. From T. cuspidatissima and T. spitzbergensis , which also have stem central strand and costa smooth ventrally, T. fleischeri (at least specimens from Russian Arctic) differ in having abrupt, V- or U-shaped transition between basal and limb cells ( Fig. 6 View Fig ).