Hedwigiaceae. Genus Hedwigia

1. Median leaf cells with mostly one branched, peltate papilla on abaxial surface 2

— Median leaf cells with 2–4 branched, usually not peltate papillae on abaxial surface 3

2. Leaf apices straight; median leaf cells strongly incrassate and porose 1. H. czernyadjevae

This species is currently known from several localities in Transbaikalia, the Verkhoyansky Range in Yakutia and the mountains of the Russian Far East (Khabarovsk Territory, Bureinsky Nature Reserve). It grows mainly in the upper forest zone (to 1750 m a.s.l.), in pine/ larch forests, usually in rock fields on dry rocks.

— Leaf apices reflexed; median leaf cells slightly incrassate, not porose [H. stellata]

This species has a more oceanic distribution than H. czernyadjevae and may occur in nothwestern European Russia or the Caucasus.

3. Plants greenish; leaves 1.25–1.8 mm long; hyaline hair-points short, usually less than 10% of leaf length; perichaetial leaves with few ciliae 3. H. nemoralis

This species occurs in the southern areas of European and Asian Russia: the Black Sea coastal areas of the Caucasus, Zabaikalsky and Primorsky Territories. Its northernmost Russian locality is in Kaluga Province (ca. 54°N). It also occurs in China and eastern North America. Hedwigia nemoralis grows on dry rocks at low altitudes in broadleaved forests, usually in humid places (sea coasts, shady forests, near waterfalls, etc.).

— Plants grayish; leaves 1.5–2.2 mm long; hyaline hair-points short to very long, usually more than 10% of leaf length; perichaetial leaves with numerous ciliae 4

4. Leaves with margins narrowly recurved in lower 1/4–1/2 5

— Leaves with margins ±widely recurved in lower 2/3–3/4 7

5. Leaves straight; hyaline hair-points 30–55% of leaf length, straight, with subentire or bluntly denti­culate margins; papillae dense, with thick round branches, obscuring cell walls 5. H. emodica var. emodica

Hedwigia emodica is the most common, widespread Hedwigia species in Russia, and is especially pervasive in the Asian parts of Russia. It commonly occurs in the Caucasus and southern Siberia from the Altai Mts. to Transbaikalia and also sporadically in Murmansk Province, Northern Urals, southern Taimyr, central/eastern parts of Yakutia, Amurskaya Province, Khabarovsk/Primorsky Territories, and Kamchatka. It is found in a wide range of altitudes extending from forest zones to alpine mountain zones. Although occasionally found in mesic habitats, more often it grows in dry conditions on dry south-faced cliffs, rock outcrops on southern slopes, and dry rocks in open places, etc.

— Leaves straight or secund; hyaline hair-points (15–)23–30(–35)% of leaf length, spreading or following leaf curvature, with narrow, sharp teeth at margins; papillae with narrow branches, not obscuring cell walls 6

6. Leaves straight, rarely slightly secund; hyaline hair-points spreading, with more or less dense papillae and spinulae in proximal portion and sparse, low papillae in distal part; median leaf cells with compact papillae, often forming longitudinal rows; European Russia and Southern Siberia 6. H. mollis

Hedwigia mollis is mostly known from forest and subalpine zones in European Russia: south of Murmansk Province; Karelia; several provinces south of Moscow (Tula, Kursk, Lipetzk); Karachay-Cherkessia and Kabardino-Balkarian Republics in the Caucasus. It occurs sporadically in the South Urals from the steppe zone in Orenburg Province (type locality) to the forest zone of Bashkortostan. It also occurs in the Altai Mts on the shore of Teletzkoe Lake and in the Chulyshman River valley. Hedwigia mollis is a somewhat calcareous species found in open and shaded, mesic to xeric habitats.

— Leaves falcate-secund, hyaline hair-points following leaf curvature, with high, dense papillae and spinulae throughout; median leaf cells with irregularly spaced papillae, not forming longitudinal rows; Russian Far East 5. H. emodica var. echinata

This variety is currently known only from the Russian Far East (Primorsky and Khabarovsk Territories, Amurskaya Province). It is a low elevation (up to 1400 m a.s.l.) mountain variety found in open, shady places on dry rocks.

7(4). Leaves straight or secund; hyaline hair-points moderately papillose; spores (27.5–)30–35(–37.5) mm; European Russia 4. H. ciliata

Hedwigia ciliata is common in NW European Russia (southern Murmansk Province, Karelia, Leningrad and Pskov Provinces) and less frequent in the Tver, Moscow and Orel Provinces of Central European Russia. The species grows mainly on granite cliffs/boulders in forests or open places and often forms large mats.

— Leaves usually straight; hyaline hair-points dens­ely papillose/spinulose; spores 23–27.5 mm; East Asian Russia 2. H. kuzenevae

The distribution of H. kuzenevae is somewhat similar to that of H. czernyadjevae (both species are also similar in appearance, but differ in papillae pattern). It is common in Amurskaya Province (Zeya Nature Reserve) and known from scattered localities in northern Zabaikalsky Territory, the Sette Daban Mt. Range in Yakutia and the lower course of the Podkamennaya Tunguska River (Evenkia). It is found at low altitudes on dry rock in open or shady places.