Pseudoleskeella, IN

KEY TO IDENTIFICATION OF PSEUDOLESKEELLA IN View in CoL RUSSIA

1. All median leaf cells with prominent single papillae at the upper ends .............................. 3. P. papillosa In View in CoL European Russia P. papillosa View in CoL is known only from the Kola Peninsula and the Urals. In Asiatic Russia the species is known from scattered localities in many relatively well explored mountain areas, except Arctic.

— Leaf cells smooth or weakly prorate or only a few cells with single, small or large papillae at the upper cell ends ................................................................ 2

2. Costae single, percurrent; axillary brood branches usually present; corticolous, rarely saxicolous ........ ........................................................... 6. P. nervosa Pseudoleskeella nervosa is a common epiphyte in the forest zone and in the forest-steppe zone of European Russia and in the Caucasus. In Asiatic Russia it occurs in southern West Siberia and in a few localities in the Russian Far East (Kamchatka; Primorsky Territory; Sakhalin Island and Kunashir Islands).

— Costae single, forked, or double, extending 0.2–0.9

the leaf length; axillary brood branches absent; saxicolous, rarely corticolous ...................................... 3

3. Costae forked or double in most leaves from both upright and creeping stems, occasionally single in some leaves ........................................................... 4

— Costae single in all leaves or single in leaves from upright shoots and forked or double in leaves from creeping shoots ..................................................... 5

4. Leaves broadly ovate or broadly ovate-triangular at the base, abruptly tapered to acumina that are 35– 50% the leaf length .......................... 1. P. tectorum In View in CoL Russia P. tectorum View in CoL is known from most well explored mountain areas and some lowlands where calcareous outcrops are more or less numerous.

— Leaves ovate or ovate-oblong at base, somewhat abruptly tapered to acumina that are 45–70% the leaf length .............................. 4. P. rupestris var. tenuis This variety is known from scattered localities in the Urals, Altai Mountains, Yakutia, and Sakhalin Island.

5. Leaf apices acute, often blunt; acumina 0.2–0.4(– 0.5) the leaf length; leaf cells 1–1.5:1, thick-walled ....................................................... 2. P. catenulata View in CoL Pseudoleskeella catenulata View in CoL occurs mainly in European Russia and the Caucasus with scattered localities in Asiatic Russia.

— Leaf apices acuminate; acumina 0.3–0.6(–0.7) the leaf length; leaf cells 1.5–3:1, moderately thick-walled .................................................................... 6

6. Leaves from creeping shoots often with double or forked costae; leaves from upright shoots with costae to 0.3–0.5(–0.7) the leaf length ......................... ....................................... 4. P. rupestris var. tenuis

— Leaves from creeping shoots with single costae; leaves from upright shoots with costae to (0.5–)0.7– 0.9 the leaf length ................................................. 7

7. Leaf acumina 0.5–0.7 the leaf length; upper leaf cells elongate-rectangular, 4–6:1 ...... 5. P. sachalinensis Russian Far East (Sakhalin Island).

— Leaf acumina 0.3–0.5(–0.7) the leaf length; upper leaf cells rhomboidal, irregularly polygonal, and rectangular, 2–4:1 ............ 4. P. rupestris var. rupestris In View in CoL Russia P. rupestris var. rupestris View in CoL is known from the Kola Peninsula, the Urals, the Caucasus, mountains of southern Siberia, and the southern Russian Far East. It occasionally occurs in northern Siberia in areas with calcareous bedrocks.