taxonID	type	description	language	source
D368BB7CFFFE604E9D8B8E784A51FADA.taxon	description	Figs. 5 – 6.	en	Ignatova, E. A., Fedorova, A. V., Kuznetsova, O. I., Ignatov, M. S. (2019): Taxonomy of the Plagiothecium laetum complex (Plagiotheciaceae, Bryophyta) in Russia. Arctoa 28 (1): 28-45, DOI: 10.15298/arctoa.28.05, URL: https://doi.org/10.15298/arctoa.28.05
D368BB7CFFF360419DD58E464A9AFE24.taxon	description	Description. Plants medium-sized, in more or less dense, somewhat rigid lustrous mats. Stems creeping, 1 – 3 cm long, foliage complanate to more commonly subcomplanate due to homomallous leaves. Leaves forming 30 – 50 ° angle with stem, curved towards substrate by their distal part, 1.3 – 2.0 (– 2.2) × 0.55 – 0.9 mm; ovate-oblong, more or less symmetric to slightly asymmetric, concave (in slides plicate and crumpled), tapered to acute apex or shortly acuminate, decurrent in 2 – 4 rows of rectangular to almost quadrate cells; leaf margins narrowly recurved on one or both sides, occasionally flat, entire or faintly denticulate at apex; costa short and double; laminal cells 80 – 150 × 6 – 10 µm. Gemmae rarely present, of 3 – 4 quadrate or short rectangular cells. Autoicous. Sporophytes usually present. Setae 15 – 20 mm long; capsules curved, inclined to horizontal, 1.5 – 2.0 mm long. Exostome teeth ca. 500 µm long; basal membrane of endostome ca. 200 µm high, segments slightly longer than exostome teeth, cilia 2, 300 µm long, distinctly nodose. Spores 9 – 12 µm.	en	Ignatova, E. A., Fedorova, A. V., Kuznetsova, O. I., Ignatov, M. S. (2019): Taxonomy of the Plagiothecium laetum complex (Plagiotheciaceae, Bryophyta) in Russia. Arctoa 28 (1): 28-45, DOI: 10.15298/arctoa.28.05, URL: https://doi.org/10.15298/arctoa.28.05
D368BB7CFFF360419DD58E464A9AFE24.taxon	distribution	Distribution and ecology. The species is rather common in European Russia, although more rare compared to P. denticulatum and P. rossicum. It occurs in boreal and hemiboreal forests of European Russia, partly in broadleaved forests, and in the Caucasus. No specimens were seen from the Asian Russia, except for eastern slope of subpolar Ural Mts. The species grows on trunk bases, fresh logs, stumps, sometimes of sandy soil on vertical banks along roads, occasionally on rocks. The habitat where this species is more common than other species of the genus are exserted roots of Pinus sylvestris in mesic to moderately dry forest types. Differentiation. Specimens of P. curvifolium are usually easy to identify due to their characteristic foliage: leaves of this species are curved towards substrate, not flattened and therefore are usually variously plicate and folded in slides under cover glass (Fig. 7). This feature is combined with partially recurved leaf margins and leaf cells variable in width (6 – 10 µm). Capsules of P. curvifolium are the longest within the P. laetum complex and are usually markedly curved and inclined; the exostome teeth are also longer than in other species of the group, ca. 500 µm long. However, some sequenced specimens with less markedly curved leaves were resolved within the P. curvifolium clade. They could most likely be confused with P. laetum, which is most similar in leaf shape (moderately asymmetrical, with acute or very shortly attenuate apical portion, and partially recurved margins). In such cases, leaf cell width may be helpful (6 – 10 µm in P. curvifolium vs. 6 – 8 µm in P. laetum). If sporophytes are present, distinctly curved capsules up to 2 mm long are characteristic for P. curvifolium rather than for P. laetum, which often has shorter capsules, straight and erect or slightly curved and inclined. As for the other two species of the P. laetum complex, P. rossicum is distinguished from P. curvifolium by flat leaf margins and narrower, 6 – 7 µm wide, leaf cells, while P. svalbardense differs from it by its smaller size, usually stronger branched stems, and a distinctly attenuate leaf apex. Selected specimens examined: EUROPEAN RUSSIA: Murmansk Province: Tersky Distr., Porja Guba, Kozhin M-M- 1785 (MW 9077455); Arkhangelsk Province: Pinega Nature Reserve, 8. VIII. 1988, Ignatov s. n. (MHA 9041583); Bolshoi Solovetsky Island, 20. VII. 1998, Churakova 235 (MW 9055387); Komi Republic: Sosnogorsk Distr., Nizhny Odes, 26. VI. 2007, Kucherov & Kutenkov 14 (MHA 9041603); Pechoro-Ilychsky Nature Reserve, Smirnova 87 (MW 9055022); Perm Province: Dobryansky Distr., Verkh-Kvazhva Setl., 3. VIII. 2005, Bezgodov & Shkaraba 36 (MW 9055024); Moscow Province: Zvenigor- od biostation of Moscow State University, 19. VI. 2018, Ignatov s. n. (MW 9110620); Vladimir Province: Aleksandrov, Seregin M- 382 (MW 9055015); Torfoprodukt, 10. IX. 2008, Kokoshnikova s. n. (MW 9055016). CAUCASUS: Republic of Karachaevo-Cherkessia: Teberda Nature Reserve, Severny Klukhor Gorge, 8. IX. 1994, Onipchenko 174 / 94 (MW 9055444). ASIAN RUSSIA: Khanty-Mansiisk Autonomous District: Berezov 16 17 18 distr., subpolar Urals, Neroika Mt., 64 ° 33 ’ 08.3 ” N, 50 ° 42 ’ 50.4 ” E, 9. VIII. 2013, Lapshina 13 - 589 (MHA 9023468).	en	Ignatova, E. A., Fedorova, A. V., Kuznetsova, O. I., Ignatov, M. S. (2019): Taxonomy of the Plagiothecium laetum complex (Plagiotheciaceae, Bryophyta) in Russia. Arctoa 28 (1): 28-45, DOI: 10.15298/arctoa.28.05, URL: https://doi.org/10.15298/arctoa.28.05
D368BB7CFFF360419DD58E464A9AFE24.taxon	materials_examined	UKRAINE: Volyn Province, Seltsy Gornitskie, 18. VII. 1949, Bradis s. n. (MW 9055303). GERMANY: Hessen, XI. 1900 Roth s. n. (E. Nauer, MEE 670; MW 9055009). POLAND: Silesia Inferior, Walbrzych, 23. VIII. 1979 Berdowski 1274 (MW 9055012); Warmian-Masurian Voivodeship, Olsztyn, S eregin & Kolodziej M- 3131 (MW 9055011).	en	Ignatova, E. A., Fedorova, A. V., Kuznetsova, O. I., Ignatov, M. S. (2019): Taxonomy of the Plagiothecium laetum complex (Plagiotheciaceae, Bryophyta) in Russia. Arctoa 28 (1): 28-45, DOI: 10.15298/arctoa.28.05, URL: https://doi.org/10.15298/arctoa.28.05
D368BB7CFFF160419DD58AAF4F0BFD6B.taxon	description	Description. Plants medium-sized, in rather dense, soft, lustrous mats. Stems creeping, 1 – 3 cm long, foliage complanate. Leaves forming 20 – 70 ° angle with stem, (1.1 –) 1.3 – 1.7 × 0.5 – 0.7 mm, ovate-oblong, more or less symmetric to slightly asymmetric, slightly concave, tapered to acute apex or shortly apiculate, decurrent in 2 – 4 (– 5) rows of rectangular cells; leaf margins entire, narrowly recurved almost throughout or at lower 3 / 4, in more asymmetric leaves occasionally recurved on one side; costa short and double; laminal cells 70 – 140 × 6 – 8 µm. Gemmae rarely present, of 3 – 4 short rectangular cells. Autoicous. Sporophytes usually present. Setae 10 – 15 mm long; capsules erect, straight or inclined, 1.0 – 1.5 mm long. Exostome teeth 400 µm long; endostome basal membrane 130 µm high, segments slightly shorter than exostome teeth, cilia 1 – 2, short, nodose. Spores 11 – 13 µm.	en	Ignatova, E. A., Fedorova, A. V., Kuznetsova, O. I., Ignatov, M. S. (2019): Taxonomy of the Plagiothecium laetum complex (Plagiotheciaceae, Bryophyta) in Russia. Arctoa 28 (1): 28-45, DOI: 10.15298/arctoa.28.05, URL: https://doi.org/10.15298/arctoa.28.05
D368BB7CFFF160419DD58AAF4F0BFD6B.taxon	distribution	Distribution and ecology. Contrary to previous publications, plants identical with Central European plants are very rare in Russia. Plagiothecium laetum s. str. was collected twice in the Caucasus, at low and middle elevations. One old specimen from Kaluga Province was also seen in the herbarium; it was collected on sandstone outcrops in a place where some rare species of mosses and vascular plants are found. Data on species ecology is scarce. According to the label information, it grows on tree bases and stumps in pine and broadleaved forests. Differentiation. Plagiothecium laetum differs from P. rossicum in always narrowly recurved leaf margins, at least partially. Flattened foliage is helpful for separating it from P. curvifolium (see also discussion under that species). From P. svalbardense it differs in larger size of plants; slightly larger leaves (1.3 – 1.7 × 0.5 – 0.7 mm in P. laetum vs. 1.2 – 1.6 × 0.35 – 0.6 mm in P. svalbardense); leaves acute or shortly apiculate vs. distinctly attenuate in the apical portion; less variable width of laminal cells (6 – 8 µm vs. 5 – 10 µm); and less branched stems on creeping shoots forming flat mats vs. stronger branched stems and loose mats. In addition, these two species have different distributions, never growing in same localities (see comments under both of them). In Eurasia, P. laetum grows in Europe, with a few localities in the Caucasus, while P. svalbardense is mainly a North Asian taxon, distributed in Europe only in its northern regions. Selected specimens examined: EUROPEAN RUSSIA: Kaluga Province: Chertovo Gorodishche, 3. IX. 1924, Zhadovsky s. n. (MW 9055355). CAUCASUS: Republic of Ingushetia: Dzheirakh Distr., Nature Reserve “ Erzi ”, 42 ° 49 ’ 57.2 ” N, 44 ° 55 ’ 06.8 ” E, 22. IV. 2018, Bersanova 18 - 159 (MW 9090994); Krasnodar Territory: Nature Reserve “ Kavkazsky ”, Babuk, Shakhe Creek valley, 43 ° 50 ’ N, 39 ° 50 ’ E, 23. VIII. 1990, Ignatov s. n. (MHA 9041733).	en	Ignatova, E. A., Fedorova, A. V., Kuznetsova, O. I., Ignatov, M. S. (2019): Taxonomy of the Plagiothecium laetum complex (Plagiotheciaceae, Bryophyta) in Russia. Arctoa 28 (1): 28-45, DOI: 10.15298/arctoa.28.05, URL: https://doi.org/10.15298/arctoa.28.05
D368BB7CFFF160419DD58AAF4F0BFD6B.taxon	materials_examined	AUSTRIA: VII. 1914, [coll. unclear] (LE). BOSNIA AND HERZEGOVINA: 10. VI. 1979, Rusinska s. n. (LE). CZECH REPUBLIC: Karlovy Vary, 12. IV. 1957, Tyuremnov s. n. (MW 9055294, MW 9055295). FINLAND: 20. VII. 1930, Railonsalo s. n. (LE). GERMANY: Lorenzer Wald bei Nürnberg, 24. VI. 1921, H. Paul s. n. (MW 9055300). HUNGARY: 14. VII. 1955, Boros s. n. (LE). NORWAY: 25. VI. 1972, Frisvoll s. n. (LE). POLAND: 20. VII. 1972, Flora Silesia exs. 1171, Bedrowski s. n. (LE). SWEDEN: 29. VIII. 1909, Möller s. n. (LE); 9. VII. 1904, Arnell s. n. (LE).	en	Ignatova, E. A., Fedorova, A. V., Kuznetsova, O. I., Ignatov, M. S. (2019): Taxonomy of the Plagiothecium laetum complex (Plagiotheciaceae, Bryophyta) in Russia. Arctoa 28 (1): 28-45, DOI: 10.15298/arctoa.28.05, URL: https://doi.org/10.15298/arctoa.28.05
D368BB7CFFF1605B9E5F89D94845FCBD.taxon	description	Description. Plants small, lustrous, in somewhat loose mats formed by variously directed stems. Stems 0.6 – 2 cm long, subpinnately or irregularly branched, foliage indistinctly complanate. Leaves forming a 30 – 70 ° angle with stem, symmetric to strongly asymmetric, concave, (0.7 –) 1.2 – 1.6 × 0.35 – 0.6 mm, ovate, gradually tapered to the apex, with attenuate apiculus, sometimes almost piliferous; cells of decurrencies in 2 – 3 rows, rectangular; leaf margins entire or minutely denticulate shortly below the apex, narrowly recurved almost throughout; costa short and double, occasionally extending beyond midleaf; laminal cells 70 – 130 × 5 – 10 µm. Gemmae of 3 – 4 short rectangular cells, occasionally present. Autoicous. Sporophytes occasionally present. Setae 5 – 10 mm long; capsules straight and erect or slightly curved and more or less inclined, 1 – 1.2 mm long. Exostome teeth 400 – 450 µm long; basal membrane of endostome ca. 130 µm high, segments slightly shorter than exostome teeth, cilia 2, 150 µm long, nodose. Spores 10 – 12 µm.	en	Ignatova, E. A., Fedorova, A. V., Kuznetsova, O. I., Ignatov, M. S. (2019): Taxonomy of the Plagiothecium laetum complex (Plagiotheciaceae, Bryophyta) in Russia. Arctoa 28 (1): 28-45, DOI: 10.15298/arctoa.28.05, URL: https://doi.org/10.15298/arctoa.28.05
D368BB7CFFF1605B9E5F89D94845FCBD.taxon	distribution	Distribution and ecology. Plagiothecium svalbardense occurs throughout the territory of Asian Russia: in permafrost zone of Yakutia and Taimyr, Amur Province, Khabarovsk and Primorsky Territories, Sakhalin, Kamchatka, mountain areas of southern Siberia, and West Siberia; in European Russia, it grows in the Urals and northern areas of lowland part (Arkhangelsk and Murmansk Provinces, Karelia). Plagiothecium svalbardense grows on various substrates, including cliffs, rock outcrops, rocks, tree bases, stumps, and rotten wood. Differentiation. According to the original description, P. svalbardense is characterized by subjulaceus foliation, ovate and distinctly apiculate leaves, and leaf cells 7 – 10 × 80 – 110 µm. Frisvoll in Frisvoll & Elvebakk (1996) emphasized that leaves of P. svalbardense are ovate and fairly suddenly narrowed into apiculus, while in P. laetum the leaves are more evenly narrowed into the short apex. He also stated that the majority of leaves in P. svalbardense are quite or almost symmetrical, while in P. laetum they are distinctly asymmetrical. In addition, he mentioned often subjulaceus and rarely complanate shoots 3 2066 1 mm 7 8 9	en	Ignatova, E. A., Fedorova, A. V., Kuznetsova, O. I., Ignatov, M. S. (2019): Taxonomy of the Plagiothecium laetum complex (Plagiotheciaceae, Bryophyta) in Russia. Arctoa 28 (1): 28-45, DOI: 10.15298/arctoa.28.05, URL: https://doi.org/10.15298/arctoa.28.05
D368BB7CFFF1605B9E5F89D94845FCBD.taxon	description	mm 5 4 6 10 11 12 bard material. Thus, they are described above for the first time. There is some resemblance in morphological traits between P. svalbardense and P. berggrenianum (ovate leaves with margins recurved from base to near the apex and suddenly narrowed apical part); however, the leaves of P. berggrenianum are much wider (0.8 – 0.9 mm vs. 0.35 – 0.6 mm), always symmetrical, leaf margins are more widely recurved, and the attenuate apical part is strongly curved and hook-shaped. There is no problem to separate P. svalbardense from P. rossicum due to always narrowly recurved leaf margins in the former species and flat margins in the latter one; in addition, shoots of P. rossicum are hardly branched and distinctly flattened, while P. svalbardense has much more branched, scarcely flattened shoots. Regarding P. curvifolium, Frisvoll (1981) mentions the similarity of “ Svalbard P. laetum ” (= P. svalbardense) with the former species in cell width, color of plants and structure of leaf decurrencies; at the same time, he states that P. curvifolium is a larger plant, it has different shape and orientation of leaves, and its distribution in Scandinavia is strictly confined to the range of conifer forest. These statements agree well with our observations of Russian material. Selected specimens examined: EUROPEAN RUSSIA: Murmansk Province: Umba, Ignatov & Ignatova 12 - 140 (MW 9055491); Porja Guba, Kozhin M-M- 0519 (MW 9055309); Alakurtti 30. VII. 1971, Konstantinova s. n. (MW 9055318); Republic of Karelia: Loukhi Distr., biostation “ Kartesh ”, 19. VII. 2017, Zakharchenko s. n. (MW 9110792); Kostomukshsky Nature Reserve, 9. VII. 1992, V. N. Korotkov s. n. (MW 9055311); Arkhangelsk Province: Pinega Nature Reserve, 5. VIII. 2006, Stepanov II- 2 (MW 9055023); same place, 30. VII. 1988, Ignatov s. n. (MHA 9041588); Komi Republic: Pechoro-Ilychsky Nature Reserve, Seregin & Zakharov M- 3425 (MW 9055632); Sosnogorsk Distr., Nizhny Odes, 5. VII. 2007, Kucherov & Kutenkov 168 (MHA 9041472); Perm Province: Basegi Nature Reserve, Ignatov & Bezgodov 743 (MW 9055417); Vishersky Nature Reserve, 5. VII. 1994, Bezgodov 379 (MW 9055427); Republic of Bashkortostan: Beloretzky Distr., projected Nature Park “ Inzer ”, 8. VII. 2005, Shirokikh 222 A (MW 9055447); Zuyakovo Settl., 1. VIII. 1990, Muldashev 89 (MW 9055446); Bolshoy Iremel’ Peak, Ignatova 6 / 11 (MHA 9041659). ASIAN RUSSIA: Tymen Province: Uvatsky Distr., Bartak River, 3. V. 2013, Bezgodov 123 (MW 9055451); Altai Republic: Kaitanak, Ignatov & Ignatova 12 - 628 (MW 9055449); Ayulyuyuzyuk, Ignatov 0 / 384 (MHA 9041722); Yailyu, Ignatov 0 / 622 (MHA 9041717); Krasnoyarsk Territory: Taimyr Distr.: Kotuy River, Fedosov 13 - 3 - 1087 (MW 9055633); Ereechka River, Fedosov 13 - 3 - 0869 (MW 9055454); Baikit Distr., Stolbovaya River, 1992, Shcherbina s. n. (MW 9055461); Zabaikalsky Territory [Chita Province]: Naminga, 26. VII. 1989, Filin s. n. (MW 9055465); Republic of Buryatia: Bol’shoy Mamai Creek, Ignatov et al. 18 - 4057 (MW 9090527); Republic of Sakha / Yakutia: Tomponsky Distr., Dyby River, Ignatov & Sofronova 17 - 366 (MW 9090011); Sette-Daban, between Ulakh and Nadezhda Creeks, Ignatov & Ignatova 16 - 1045 (MW 9078473); Kyurbelyakh Creek, 63 ° 08 ’ N, 139 ° 04 ’ E, 8. VII. 2011, Ignatov & Ignatova 11 - 2164 (MW 9055468); Ulakhan-Chistai Mt. Range, Ignatov & Ignatova 18 - 2123 (MHA 9028887); Orulgan Mt. Range, Tumara, Ignatov 11 - 4468 (MW 9055466); Oimyakon Distr., Mus-Khaya Mt., Ignatov & Ignatova 11 - 3022 (MW 9055467); Ust-Maya Distr., Allakh-Yun, Ignatov 00 - 878 (MHA 9041471); Nature Park “ Lena Pillars ”, Ignatov & Ignatova 16 - 330 (MW 9077452); Amurskaya Province: Zeya Nature Reserve, Dudov & Kotelnikova 2014 _ Br _ 9139 (MW 9079826); Norsky Nature Reserve, 6. VII. 2010, Bezgodov 228 (MHA 9041681); Khabarovsk Territory: Bureinsky Nature Reserve, 8. VIII. 1992 Borisov s. n. (MW 9055482); Botchi State Reserve, Ignatov & Ignatova 13 - 60 (MW 9055474); Primorsky Territory: Shkotovo Distr., Pidan Mt., Ignatov & Ignatova 06 - 2111 (MW 9055479); Chuguevka Distr., Berezovy Creek, Ignatov 07 - 232 (MW 9055477); Terney Distr., Isakov Creek, Ignatov & al 13 - 1820 (MW 9055029); Kamchatsky Territory: Kamchatka Peninsula, Elovka River, 29. VIII. 2003, Czernyadjeva 115 (MHA 9041706); Sakhalinskaya Province: Sakhalin Island, Nogliki Distr., Gortachie Klyuchi station, Pisarenko op 03391 (MHA 9041462). Localities confirmed by J. Wynns (pers. corr. May 2019): * GREENLAND: K. Holmen & G. Mogensen 71 - 1916, sub P. laetum; Kangerdluatslaq, Arveprinsens Ejland [W 5], 69 ° 52 ’ N, 50 ° 47 ’ W, 12 Aug 1971, C; K. Holmen & G. Mogensen 71 - 2531, Ivnaq, Arveprinsens Ejland, 69 ° 48 ’ N, 51 ° 14 ’ W, 14 Aug 1971, sub P. piliferum, C; K. Holmen & G. Mogensen 71 - 2532, idem, sub P. laetum, C; K. Holmen & G. Mogensen 71 - 2538, idem, C; K. Holmen & G. Mogensen 71 - 2552, idem, sub P. denticulatum, C; J. Lewinsky 73 - 948, Kilaersarfik, Ameragdla, Godthĺb distr. [W 3], 64 ° 15 ’ N, 50 ° 12 ’ W, 1 Aug 1973, sub P. laetum, C. NORWAY: Musci Spetsbergenses Exsic. 122 p. p., Parrys I, Spitsbergen [Svalbard], 1868, UC no. 1752324. SWE- DEN: T. Westergren 204, Kvikkjokk, Lapponia Lulensis, original specimen of P. westergrenii, HBG. Plagiothecium berggrenianum Frisvoll, Lindbergia 7 (2): 96 – 98, f. 2. 1981 [1982]. Fig. 11. Description. Plants medium-sized to large, in loose lustrous mats, often growing by individual shoots in tufts of other mosses or hanging down a cliff surface. Stems 1 – 3 cm long, poorly branched, foliage julaceous. Leaves appressed, directed upwards, symmetric, strongly concave (in slides plicate and crumpled), 1.4 – 1.6 × 0.8 – 0.9 mm, broadly ovate, cucullate at apex, abruptly narrowed to a hooked, reflexed apiculus, longly decurrent, cells of decurrencies in 2 – 4 rows, rectangular, sometimes round close to leaf base; leaf margins entire or minutely serrulate shortly below apex, more or less widely recurved almost throughout; costa short and double, occasionally extending beyond midleaf; laminal cells 75 – 130 × 7 – 9 µm, thick-walled. Gemmae of 3 – 4 short rectangular cells, occasionally present. Autoicous. Setae 2 – 2.2 mm long; capsules straight and erect or slightly curved and more or less inclined, 1 – 1.2 mm long. Exostome teeth ca. 450 µm long; cross-striolate below, slightly papillose in upper half; endostome basal membrane ca. 180 µm long, segments slightly longer than exostome teeth; cilia 2, up to as long as segments, nodose to appendiculate. Spores 15 – 21 µm.	en	Ignatova, E. A., Fedorova, A. V., Kuznetsova, O. I., Ignatov, M. S. (2019): Taxonomy of the Plagiothecium laetum complex (Plagiotheciaceae, Bryophyta) in Russia. Arctoa 28 (1): 28-45, DOI: 10.15298/arctoa.28.05, URL: https://doi.org/10.15298/arctoa.28.05
D368BB7CFFF1605B9E5F89D94845FCBD.taxon	distribution	Distribution and ecology. This northern species is not rare in permafrost areas of Asian Russia (Taimyr Peninsula and adjacent areas, Yakutia, Chukotka, Magadan Province); it extends southward up to ca. 61 ° N (Ust-Maya District of Yakutia). It is also known from islands of the Arctic Ocean, Svalbard and Franz Josef Land. In North America it is confined to the northernmost areas, including Greenland, Alaska and NW Territories. Grows on wet cliffs and rocks along water courses, in shady niches under boulders, on moist turf and humus in shady places, in tundra and Sphagnum bogs, occasionally on rotten wood. Forms pure mats or grows as solitary shoots in tufts of other mosses. Differentiation. Plagiothecium berggrenianum is a conspicuous plant due to a combination of such morphological characters as large size of plants and appressed, symmetrical, ovate, strongly concave leaves with distinctly recurved margins and hook-shaped apiculus. It makes unlikely its confusing with any species of the P. laetum complex (see, however, discussion under P. svalbardense). Sporophytes and gametangia of P. berggrenianum were unknown from Svalbard and not described in the protologue. Later sporophytes of this species were found in the Russian Arctic (West Siberia, Yamal) and described by Ukrainskaya (1996), who mentioned a dioicous sexual condition, erect or slightly inclined capsules, absence of cilia and large size of spores (15 – 17 µm). Sporophytes of P. berggrenianum were also illustrated by Ignatov et al. (2001), who found this species in Ust-Maya District of Yakutia (one of southernmost localities). Cilia were drawn as short, and sexual condition was described as autoicous (at least some shoots with both antheridia and archegonia were observed). Since that time more collections of P. berggrenianum were made in Asian Russia. According to our observations, an autoicous sexual condition is confirmed; cilia of endostome may be almost as long as segments, nodose to almost appendiculate; and spores are sometimes even larger, 15 – 21 µm. Selected specimens examined: ASIAN RUSSIA: Yamalo- Nenetsky Autonomous Distr.: Yamburg 25. VII. 2014, Bezgodov 239 (PPU 6896); Yunto Lake, 2. VIII. 1993, Czernyadjeva 13 (LE); Gydan Peninsula, 11. VII. 1991, Czernyadjeva 24 (LE); Ngaranato Lake, 19. VIII. 1992, Czernyadjeva 21 (LE); middle course of Sebayakha River, 22. VII. 1992, Czernyadjeva s. n. (LE); middle course of Khabeyakha River, 31. VII. 1981, Rebristaya 38 (LE); Krasnoyarsk Territory: Byrranga Mts., Fedosov Plt 7 (MW); Medusa Bay, 6. VII. 2002, Varlygina s. n. (MW 9054793); Ledyanaya Bay of Taimyrskoe Lake, Fedosov P 87 (MW 9054797); Kotuikan River, Fedosov 11 - 607 (MW 9054787); Afanas’evskie Lakes, Fedosov 06 - 589 (MW 9054790); Ary-Mas biostation, Fedosov 07 A- 1 - 17 (MW 9054789); same place, 30. VII. 1972, Norin s. n. (LE); Ereechka River, Fedosov 13 - 3 - 0469 (MW 9054785); Republic of Sakha / Yakutia: Orulgan Mt. Range, Ignatov 11 - 4182 (MW 9054800); Kyurbelyakh Creek, Ignatov & Ignatova 11 - 2178 (MW 9054802); Oimyakon Distr., Mus-Khaya Mt., Ignatov & Ivanov 11 - 3582 (MW 9054804); Ust-Nera Settl., Tas- Kystabyt Range, Ignatov & Ignatova 15 - 1222 (MW 9054799); Nizhnekolymsk Distr., 8. IX. 1972, Stepanova s. n. (MW 9054805); Lower course of Indigirka River, Malaya Ercha Creek, 2. VIII. 1974, Afonina s. n. (LE); Anabar Distr.: Anabar River basin, Andreev 8244 / 2 (SASY); Saskylakh Settl., Andreev 8248 / 2 (SASY); upper course of Kele River, Andreev 8246 / 2 (SASY); Verkhoyansky Distr., Elgetsk, Isakova 8250 / 2 (SASY); Chukotsky Autonomous District: Providensky Distr., Arakamchechem Island, Afonina A- 35 (LE); St. Laurence Bay, 25. VII. 1934, Gorodkov s. n. (LE); Place of confluence of Chegitun and Khesmymken Rivers, 24. VIII. 1982, Katenin & Popov s. n. (LE); Karvakyanskaya Creek, 27. VII. 1982, Afonina s. n. (LE); Egvekinot, 16. VIII. 1985, Afonina s. n. (LE); Magadan Province: Okhotskoe Sea coast, Kamenny Range, Ermolenko op 06803 (NSK 2006803); Kamchatsky Territory: Sobolevsky Distr., Pravy Kikhchik River basin, 23. VII. 2004, Czernyadjeva 15 (LE). Localities confirmed by J. Wynns (pers. corr. May 2019): * CANADA: NUNAVUT: Resolute Bay, Cornwallis Island, 74 ° 41 ’ N, 94 ° 50 ’ W, 10 m, 14 July 1990, Mogensen 90 - 306, C. GREENLAND: Egedesminde, Tupilak Island [W 4], 68 ° 42 ’ N, 52 ° 55 ’ W, 30 June 1956, sub P. laetum, Holmen 15554, C. USA: ALASKA: vicinity of Point Barrow, SE of Laboratory, 71 ° 40 ’ N, 156 ° 38 ’ W, 2 – 3 m, 18 June 1973, Steere et al. 73 - 1, NY no. 159489; between National Arctic Research Laboratory and gas well, idem, 19 June 1973, Steere et al. 73 - 2, NY no. 159491; Meade River Post Office (Coal Mine), 70 ° 28 ’ N, 157 ° 25 ’ W, ca. 30 m, 12 – 15 July 1973, Steere et al. 73 - 372, NY no. 159490.	en	Ignatova, E. A., Fedorova, A. V., Kuznetsova, O. I., Ignatov, M. S. (2019): Taxonomy of the Plagiothecium laetum complex (Plagiotheciaceae, Bryophyta) in Russia. Arctoa 28 (1): 28-45, DOI: 10.15298/arctoa.28.05, URL: https://doi.org/10.15298/arctoa.28.05
