Dicranum japonicum Mitt., Trans. Linn. Soc. Bot.

Dicranum japonicum Mitt., Trans. Linn. Soc. Bot. View in CoL ser. 2, 3: 155. 1891. Figs. 4–6.

Type: ‘Challenger’ Exp.; Oyama and Fujisan, barren, Bisset.

NY herbarium has two syntypes: the putative lectotype “ J. Bisset 26 Oyama” ( NY 1093852 ; scans at https:/ /sweetgum.nybg.org/science/vh/specimen-details/?irn=1238206) and ‘Challenger’ Exp. ( NY 1093851 ; scans at https://sweetgum.nybg.org/science/vh/specimen-details/?irn=1238204) .

PC herbarium has two isosyntypes: (1)‘Challenger’ Exp. ( PC0128669 ); (2) Oyama and Fujisan, Bisset. ( PC0128670 ). Scans: https://science.mnhn.fr/institution/ mnhn/collection/pc/item/pc0128669 .

Plants medium-sized to large, in loose tufts, glossy, yellowish-green. Stems 4–5(–12) cm, densely or loosely foliate, with dense, whitish to brownish tomentum throughout. Leaves straight, patent to patulous when wet and dry, sometimes slightly flexuose-secund, 8–9(–11) × 0.9–1.1 mm, from ovate-lanceolate base gradually narrowed into long, narrow acumina, concave proximally, keeled distally; margins plane, serrate distally, unistratose; costa 1/9–1/11 of leaf width at base, percurrent or ending before apex, in distal part on abaxial surface with 2–3(–4) serrate ridges 1–2(–3) cells high, in transverse sections with one row of guide cells, two stereid bands, adaxial epidermal layer of cells not differentiated, in the basal parts of leaves the abaxial stereid layer interrupted by several enlarged cells; lamina unistratose, cells irregularly mammillose, often oblique in leaf transverse sections; distal laminal cells linear, (68–)80–112(–136) ×(11.5–)12.5–15.5(–18) µm, thick-walled, porose; proximal laminal cells (75–)82–130(–173)×(14–)16–19(–20) µm, moderately thick-walled, porose; alar cells well-differentiated, brownish, 2–4 stratose, not reaching the costa. Phyllodioicous. Male plants dwarfed, on rhizoidal tomentum of female plants. Inner perichaetial leaves abruptly long-acuminate, convolute-sheathing. Setae solitary, 4–5(–6) cm. Capsules inclined, asymmetrical, urns 2.5–3(–4.5) mm long, slightly curved, furrowed when dry. Spores 13–24 µm, papillose.

Distribution and habitats. Dicranum japonicum was reported from Japan, China, and Korea (Takaki, 1964; Gao et al., 1999). In Russia this species is rare; it occurs in monsoon climate of the Far East: in Kamchatka Peninsula, Kuril Islands and Primorsky Territory. It grows on soil, rocks covered with humus and forest litter, in open sites and in mixed forests. In Japan “this species most frequently grows on humus-rich soil in moderately moist and shaded places where this species forms sometimes wide pure carpets as does D. scoparium ” (Takaki, 1964, p. 117) .

Variation. There is a slight variation in size of distal laminal cells in specimens from the Russian Far East in comparison with the type specimen. For example, the cells in Kunashir specimens of D. japonicum are (63–) 88–128(–143)×13–17(–20) µm and in specimens from Primorsky Territory (47–)72–112(–143) ×(14–)15.5–20 (–24) µm. These cells are wider then in the type specimen. Alar cells in the upper young leaves often are only 2-stratose. In the Moss flora of Japan ( Noguchi & Iwatsuki, 1987) upper laminal cells are described as 45–80 µm long. We also studied few specimens of Mosses of Japan Exsiccati (№1252, Fasc. XXXI (2010), №6, Fasc. 1. (1987)) and duplicates of D. japonicum specimens from Japan. They had upper laminal cells 50–75 µm long and 2-stratose alar cells. Only one studied specimen from Japan (№1311) had longer laminal cells and 2–4-stratose alar regions.

Distinctions. Dicranum japonicum resembles D. polysetum by patent stem foliation; however, its leaves are smooth vs. strongly transversely undulate. Its distal laminal cells are longer, starting from 70 µm vs. from 40 µm in D. polysetum . It also has single sporophytes in perichaetia vs. 3–7 in D. polysetum . Long upper leaf cells of D. japonicum are similar the the upper leaf cells of D. orthophyllum ; however, they differ in having patent to patulous vs. erectopatent to appresed leaves; 2–4-layered alar cells vs. 2-layered; and inclined, asymmetric, slightly curved vs. cylindrical, straight capsules. Differences between D. japonicum and D. baicalense are discussed in the comments to this species. The differences of D. japonicum from other species of the genus Dicranum with ridges on the dorsal surface of the costa are given in Table 1.

Specimens examined: RUSSIA: Kamchatka Territory , Kamchatka Peninsula, vicinity of Puschino Village , upper Kamchatka River , 54°11’N, 158°02'E, birch-grass forest with row- an on the slope of the hill, 16 September 1978, Afonina P-7 ( LE, UUH) GoogleMaps with sporophytes and dwarf male plants. Primorsky Territory, Lazovsky District, vicinity of Chistovodnoe Village , N slope of cliff, on rocks, 13 September 1977, Bardunov et al. s.n. ( IRK, UUH) . Sakhalin Province: (1) Kuril Islands, Kunashir Island, Mendeleev Volcano , Kisly Sream 44°00'N, 145°46'E, 10 alt., moss coniferous forest, on forest litter, 10 October 2006, Ignatov 06-3129 ( MHA, UUH) GoogleMaps with sporophytes and dwarf male plants; (2) same place, 43°59’08.4"N, 144°00’03.5"E, 172–452 alt., bamboo spruce forest with an admixture of broad-leaved trees, on soil, 07 August 2014 Tubanova et al. K14035 View Materials /87 ( UUH) GoogleMaps . JAPAN: Kyushu, Kagoshima-ken, Isl. Yakushima , Hanano-ego , on soil at open site, 1600 alt., 27 September 1975, Iwatsuki & Suzuki Exsiccatii 1311, Ser. 27 ( LE, UUH) . CHINA: Guizhou Province, Kaijang County, Xiang Zhi Stream , 26°46’59.5"N, 106°54’44.5"E, 1200 alt., broadleaved (mostly evergreen) forest on steep slope to valley of stream, mesic condition clay on slope, in part shade, 19 November 2013, Bakalin China-51-60-13 ( VBGI, UUH) GoogleMaps .