Grimmiaceae. Genus Niphotrichum
1. Leaves elliptic to broadly ovate-lanceolate, obtusely keeled above, broadly channeled; costae to 1/2 leaf length, usually forked near tips; upper leaf papillae large and conspicuous —
— Leaves ovate-lanceolate to ovate-triangular, sharply keeled above, narrowly channeled; costae to 3/4 leaf length, usually not forked near tips; upper leaf papillae small and inconspicuous —
2. Basal leaf cells distinctly papillose; hyaline hair-points entire to weakly serrulate (often only near tips), papillose throughout —
1. N. canescens
In European Russia this species is common in Murmansk Province and Karelia but scattered southward and known from only a few records in the central and southern parts (Saratov and Volgograd Provinces). It is frequent throughout the Caucasus and sporadic in Urals. In Asian Russia it is fairly common in Altai Mts. and widespread but not frequent throughout the mountain areas of Siberia, becoming common in Kamchatka and Chukotka. In the Arctic it is represented by subsp. latifolium. Distinctive features that help to identify this species include widely canaliculate leaves with short, branched costae and large papillae centered over the upper leaf cell lumina. It differs from N. panschii in hair-point structure: N. canescens, densely papillose throughout and moderately serrate at margins; N. panschii, papillose in lower parts but smooth or nearly so above and coarsely serrate.
— Basal leaf cells smooth or weakly papillose; hyaline hair-points serrate throughout, smooth to weakly papillose above —
2. N. panschii
Rather frequent in the Arctic regions of Asian Russia, fairly common throughout permafrost zone of Siberia and northern Far East, rather common in mountain areas of southern Siberia (but known from only a few localities in Altai Mts. ), sporadic in Kamchatka, Kommander Islands and southern part of Russian Far East. For its distinctions from N. canescens see comments under that species.
3. Plants large; basal leaf cells with high, large papillae, median leaf cells with lower, smaller papillae; alar group large, distinctly demarcated with 6-8(-10) rows of thin-walled, inflated alar cells; hyaline hair-points stout, spinose —
7. N. japonicum
Rare species known from a few localities in southern Russian Far East (Sakhalin, Primorsky Territory and Evreiskaya Province). It can be recognized by its large plants; weakly branched stems; narrowly keeled leaves with long costae; long recurved leaf margins; and stout, coarsely spinose hair-points. An especially noteworthy feature of this species is the presence of exceedingly large papillae centered over the basal leaf cell lumina that strongly contrast with the small papillae at mid-leaf.
— Plants medium-size to rather large; basal leaf cells with papillae similar to median leaf cell papillae or basal leaf cells almost smooth; alar group small, indistinctly demarcated, with 3-7 rows of enlarged alar cells; hyaline hair-poinst subulate, not or weakly spinulose —
4. Leaf margins reflexed to 1/2-3/4 leaf length —
— Leaf margins reflexed almost to apices or base of hyaline hair-points —
5. Hyaline hair-points usually long, subulate, serrulate, decurrent; basal leaf cells long, narrow with strongly incrassate walls and weak, inconspicuous papillae, clearly different from short, strongly papillose median leaf-cells; alar group weakly developed with 5-7 cell rows; pellucid marginal border at leaf base extending 1/5-1/2 leaf length —
5. N. barbuloides
Collected once in western part of Kamchatka, at 500 m a. s. l. It can be recognized by its small, pinnately branched plants; leaves contorted when dry state; shortly recurved leaf margins; inconspicuous alar groups; well-formed hyaline borders at leaf base; and thick-walled, weakly papillose to almost smooth, basal juxtacostal cells.
— Hyaline hair-points absent or very short, lowly papillose, not decurrent; basal leaf cells indistinctly different from median leaf-cells; alar group better developed with 3-8 cell rows; pellucid marginal border at leaf base indistinct —
6. N. muticum
Found in several localities in Kamchatka and Kommander Islands. Distinctive features of this species include slender, pinnately branched plants; flexuose leaves with narrow, muticous apices or with very short hyaline apicula; uniformly papillose leaf cells; and weakly developed marginal leaf borders at base.
6. Hyaline hair-poinst straight to slightly flexuose when dry, weakly papillose to smooth above, not or only slightly decurrent; leaf basal marginal borders pellucid, well developed, formed by elongate, non-sinuous, thin-walled cells —
3. N. ericoides
Arctic species rather common in islands of Arctic Ocean, in Taimyr, Arctic Yakutia and Chukotka, extends southward to Kamchatka and known from a few localities in Primorsky Territory and Kuril Islands. Grows in the mountain tundra zone. It can be distinguished from other species of the genus by its medium-sized, pinnately branched plants and sharply keeled leaves with long costae; longly recurved margins; narrow, smooth or weakly papillose, straight hair-points; and small upper leaf cell papillae.
— Hyaline hair-points sharply bent when dry, conspicuously papillose throughout, decurrent; leaf basal marginal borders not or poorly developed —
4. N. elongatum
This species was reported from Kaliningrad Province and recently found at several localities in the Russian Caucasus (Karachaevo-Cherkessian Republic and Krasnodar Territory) and in oceanic areas in the Russian Far East (Kuril Islands and Kamchatka). It is very similar to N. ericoides in most characters, but differs it having recurved tips of branches and reflexed hair-points that are more stronger papillose and longer decurrent.