Hattoria 11: 41–60. 2020

New national records and range extensions of the genus Fissidens (Fissidentaceae) from Guangxi, China

Qi-Ming TANG1, Boon-Chuan HO2 & Yu-Mei WEI1

1 Guangxi Key Laboratory of Conservation and Restoration Ecology in Karst Terrain, Guangxi Institute of Botany, Guangxi Zhuang Autonomous Region and Chinese Academy of Sciences, Guilin 541006, Guangxi, China 2 Singapore Botanic Gardens, National Parks Board, 1 Cluny Road, Singapore 259569, Republic of Singapore Author for correspondence: Yu-Mei WEI, [email protected]

Abstract Three species of Fissidens, viz. F. gracilifolius Brugg.-Nann. & Nyholm, F. laxitextus Broth. ex Gangulee and F. pseudoclosteri Z.Iwats. & S.S.Kumar are newly reported for China. In addition, seven species, viz. F. beckettii Mitt., F. flabellulus Thwaites & Mitt., F. jungermannioides Griff., F. kinabaluensis Z.Iwats., F. serratus Müll.Hal., F. subangustus M.Fleisch., and F. wichurae Broth. & M.Fleisch. are new provincial records for Guangxi. Photographs and diagnostic characters to help distinguishing the new records are provided.

Introduction Guangxi (short for Guangxi Zhuang Autonomous Region) is located in southern China (20°54′–26°24′N, 104°26′–112°04′E). Its total land area is 236,275 km2, including three climatic zones from the northern tropical to southern and central subtropical zones. As a mountainous province, hilly mountain terrain in Guangxi occupies an important share (75.6% of its total land area). The elevation ranges from sea level to 2,142 m (Mao’er Mountain). In addition, Guangxi also occupies large parts (89,544 km2) of the South China Karst, a UNESCO World Heritage Site since June 2007. With complex geographical landforms, favourable climatic conditions, and rich water resources, Guangxi is abundant in animals and resources, for example, the vascular plant biodiversity is ranked the third highest among the Chinese provinces (Qin & Liu 2010). Similarly, the diverse range of microhabitats nurture a bountiful bryoflora. In our recently compiled checklist of bryophytes in Guangxi, a total of 1,230 species have been reported (Wei et al. 2018b). Of these, 33 species are Fissidens, representing more than half of the total number of Fissidens species known from China (65 species; Jia 2018). Subsequently, Wei et al. (2018a) added two more species (F. bogoriensis M.Fleisch. and F.

41 ganguleei Nork.) and one variety [F. crispulus var. robinsonii (Broth.) Z.Iwats. & Z.H.Li] to the Fissidens-flora in southwest Guangxi. As a mainly tropical and subtropical distributed genus, the actual diversity of Fissidens in Guangxi is expected to surpass the currently known number. Based upon this prediction, and on other interesting finds e.g. the rare and endemic Japanese species, Soella obtusifolia (T.Yamag.) R.L.Zhu, L.Shu, Qiong He & Y.M.Wei (previously named Drepanolejeunea obtusifolia T.Yamag.) and apiculata Z.Iwats. & Nog., discovered in Guangxi (Zhu et al. 2018; Tang et al. 2019), we have launched a province-wide investigation of bryophytes in Guangxi. During this research, we intend to pay special attention to the genus Fissidens.

Materials and Methods Since 2018, 250 specimens of Fissidens have been collected in Guangxi. All the specimens are deposited in the herbarium of Guangxi Institute of Botany (IBK). Identifications were based mainly on major taxonomic works on Fissidens in China and Japan (e.g. Iwatsuki & Suzuki 1982; Li & Iwatsuki 2001; Suzuki 2015) and other references mentioned under the following section. The new records are arranged alphabetically, where new records for China are marked with an asterisk (*). Each is provided with a diagnosis and a short discussion of species likely to be confused with it. For species newly recorded to China, a detailed description is provided based on the cited specimens. With regards to costa types and peristome types we refer to those described by Suzuki & Iwatsuki (2007) and Suzuki et al. (2018). Field images were photographed with a digital camera (Canon G16). The morphological and anatomical characters were observed and photographed using an Olympus SZX7 stereomicroscope and an Olympus BX43 light microscope equipped with a digital camera (Mshot MH125).

Results and Discussion Among these collections, ten species are newly recorded for the bryoflora of Guangxi. Three of these, namely Fissidens gracilifolius Brugg.-Nann. & Nyholm, F. laxitextus Broth. ex Gangulee and F. pseudoclosteri Z.Iwats. & S.S.Kumar, are new to China. The remaining seven, viz. F. beckettii Mitt., F. flabellulus Thwaites & Mitt., F. jungermannioides Griff., F. kinabaluensis Z.Iwats., F. serratus Müll.Hal., F. subangustus M.Fleisch., and F. wichurae Broth. & M.Fleisch., are new provincial records. As a result, the number of Fissidens in Guangxi has risen to 46 species. This is just the beginning of a comprehensive study of Fissidens in Guangxi. More noteworthy discoveries of bryophytes, especially in the species- rich genus Fissidens is postulated in the course of our on-going project on the inventory study of bryophytes in Guangxi.

New Species Records for Guangxi 1. Fissidens beckettii Mitt., J. Linn. Soc., Bot. 13: 325. 1873. Fig. 1 This species is characterised by 1) small plants (1–3 mm tall) and simple stems, 2)

42 non-differentiated axillary hyaline nodules, 3) ovate-lanceolate or lanceolate leaves with excurrent costa, 4) well-developed limbidia along the entire margins of leaves sometimes ending near the base of dorsal lamina, 5) open and unequal vaginant laminae, 6) smooth and large laminal cells (13–25 µm long), 7) rhizautoicous inflorescence, 8) curved and asymmetric capsules, and 9) Fissidens-type peristome teeth. Specimens examined: CHINA. Guangxi: Leye Co., Yachang Orchid National Nature Reserve, 24°44′51.00″N, 106°20′20.69″E, 1,755 m elev., on soil, 19 May 2019, Tang 20190519-337 (IBK); Gongcheng Co., Yindianshan Nature Reserve, 24°49′57.06″N, 110°58′38.86″E, 486 m elev., on soil, 11 April 2020, Tang 20200411-9 (IBK). Distribution: mainly distributed in pantropical area (Bruggeman-Nannenga 2013), occurring also in Australia (Stone 1994) and Russia (Ignatov & Suzuki 2018). In China, previously only known from Guizhou and Guangdong (Jia 2018), new to Guangxi.

2. Fissidens flabellulus Thwaites & Mitt., J. Linn. Soc., Bot. 13: 324. 1873. Fig. 2 This species is characterised by 1) small plants (0.60–1.45 mm tall) and mainly simple stems, 2) well-differentiated axillary hyaline nodules, 3) lanceolate leaves with subpercurrent to percurrent costa, 4) crenulate or serrulate leaf margins, 5) smooth to slightly mammillose laminal cells, 6) rhizautoicous inflorescence, 7) erect and symmetrical capsules, and 8) Fissidens-type peristome teeth. Representative specimens examined: CHINA. Guangxi: Daxin Co., Encheng National Nature Reserve, 22°45′25.78″N, 107°4′59.15″E, 347 m elev., on soil, 20 September 2018, Tang 20180920-126 (IBK); Shangsi Co., Shiwandashan National Nature Reserve, 21°50′59.74″N, 107°53′12.48″E, 479 m elev., on soil, 20 August 2019, Tang, Wei & Huang 20190824-36 (IBK). Distribution: China [Hainan, Yunnan, Taiwan (Jia 2018), new to Guangxi], Australia, Fiji, India, Japan, Malaysia, New Caledonia, Papua New Guinea, Sri Lanka, Thailand (Tan et al. 2006b; Suzuki & Iwatsuki 2011). Notes: Fissidens flabellulus closely resembles F. serratus, and was previously considered as a synonym (Fleischer 1904; Eddy 1988). Tan et al. (2006b) found F. flabellulus to be distinct from F. serratus by its crenulate leaf margin (sharply serrate in F. serratus), its smooth to mammillose laminal cells (unipapillose in F. serratus), and well-differentiated axillary hyaline nodules (weakly differentiated in F. serratus). In the Guangxi-collections we observed no difference with regards to the leaf margins, but found the two species to be distinct by the other two characters (see also Iwatsuki & Suzuki 1982).

3. *Fissidens gracilifolius Brugg.-Nann. & Nyholm, Ill. Fl. Nord. 1: 10. 1986. Fig. 3 Plants light green to dark green, growing in short and loose tufts. Stems simple. Fertile and sterile stems dimorphic, fertile stems 1.55–2.50 mm with 3–5 pairs of leaves; sterile stems rare in our specimens, juvenile; axillary hyaline nodules not differentiated; cortical cells in cross section small, thick-walled, central strand weakly differentiated. Upper leaves narrowly lanceolate, acute at apex; base of dorsal lamina wedge shaped, more or less decurrent; costa ending 2–4 cells below leaf apex, bryoides-type; margins weakly serrulate near leaf apex; vaginant lamina about 1/2 of leaf length, unequal; limbidium ending below leaf apex, usually

43 Figure 1. Fissidens beckettii Mitt. A: Habit. B–D: Plants. E–F: Leaves. G: Perichaetial leaf. H–I: Transverse sections of leaf. J: Peristome teeth. K: Exothecial cells. L: Leaf apex. M: Distal part of vaginant lamina N: Basal part of vaginant lamina. O: Transverse section of stem. All figures taken from Tang 20200411-9.

44 Figure 2. Fissidens flabellulus Thwaites & Mitt. A: Habit. B: Plants. C–D: Leaves. E– F: Perichaetial leaves. G–H: Transverse sections of leaf. I: Leaf apex. J: Leaf base. K: Exothecial cells. L: Peristome teeth. M: Portion of stem with leaves removed, showing the well-differentiated axillary hyaline nodules. N: Transverse section of stem, axillary hyaline nodule on the right. All figures taken from Tang et al. 20190824-36.

45 Figure 3. Fissidens gracilifolius Brugg.-Nann. & Nyholm. A: Habit. B–D: Plants. E–F: Leaves. G–H: Perichaetial leaves. I: Transverse section of stem. J–K: Transverse sections of leaf. L: Leaf apex. M: Leaf base. N: Exothecial cells. O: Peristome teeth. All figures taken from Tang & Zhang 20181004-429A.

46 turning yellowish brown in old leaves when treated with KOH, 1–2 rows of cells wide on apical lamina, 3–5 rows on vaginant lamina, in cross section 1–2 cells thick; laminae unistratose; cells of apical lamina irregularly quadrate to hexagonal, 7.5–11.5 µm long, smooth, thin walled. Rhizautoicous; perigonia at base of stem; seta terminal, 2.8–4.0 mm long; capsule erect, symmetrical; urn ovoid, 0.55–0.70 mm long; exothecial cells rounded quadrate to rounded rectangular; operculum rostrate; peristome teeth Fissidens-type; calyptra cucullate. Specimen examined: CHINA. Guangxi: Leye Co., Yachang Orchid National Nature Reserve, 24°44′55.78″N, 106°19′16.47″E, 1,457 m elev., on rock, 4 October 2018, Tang & Zhang 20181004-429A (IBK). Distribution: Europe, Japan (Suzuki & Iwatsuki 2012), new to China (Guangxi). Notes: Fissidens gracilifolius is recognised by 1) fertile and sterile stems dimorphic, 2) axillary hyaline nodules not differentiated, 3) costa ending below leaf apex, 4) limbidium ending below leaf apex, and 5) cells of apical lamina smooth, thin walled. Fissidens gracilifolius bears much resemblance to F. crassipes Wilson ex Bruch & Schimp., both having the similar limbidium, same reaction to KOH, and similar cell shape of apical lamina. Fissidens crassipes, however, differs in being synoicous and cell size of apical lamina larger (13–20 µm in F. crassipes, refer to Suzuki & Iwatsuki 2013).

4. Fissidens jungermannioides Griff., Calcutta J. Nat. Hist. 2: 504. 1842. Fig. 4 This species is characterised by 1) medium-sized plants (up to 13.5 mm tall) green when young, becoming reddish brown when older, 2) non-differentiated axillary hyaline nodules, 3) lanceolate leaves with percurrent to slightly excurrent costa, 5) margins of apical and dorsal laminae forming a thick and dark coloured band of 2–4 cells wide and 2–3 cells thick, and 6) smooth to slightly mammillose laminal cells with thick walls. Specimens examined: CHINA. Guangxi: Jingxiu Co., Dayaoshan National Nature Reserve, 500–700 m elev., on frequently dripping wet cliff, 4 May 2018, Tang 20180504-21A (IBK); Longsheng Co., Longji Town, Dinglingjie, 25°44′58.16″N, 110°7′46.22″E, 405 m elev., on wet rock with a thin layer of soil in mountain stream with intermittent flow, 15 July 2019, Tang, Wei, Huang & Liao 20190715-3 (IBK), 21 April 2020, Tang & Wei 20200422-1 (IBK). Distribution: China [Guangdong, Guizhou, Hunan, Taiwan (Jia 2018), Hong Kong (Zhang 2003), new to Guangxi], India, Thailand (Wongkuna et al. 2009). Notes: Among the Chinese Fissidens, only three species share the character of a thick and dark band along the leaf margins: F. jungermannioides, F. javanicus Dozy & Molk. and F. nobilis Griff. These species are probably not closely related (compare Suzuki et al. 2018) and easily distinguishable from each other: Fissidens jungermannioides has smaller plants size (8–18 mm tall in F. javanicus, 18–60 mm in F. nobilis), non-differentiated axillary hyaline nodules (well-differentiated in F. javanicus), smooth to slightly mammillose laminal cells (distinctly mammillose in F. javanicus and F. nobilis), and non-decurrent dorsal laminal base (distinctly decurrent in F. nobilis). According to Suzuki et al. (2018), the thickened dark bands of the laminae in Fissidens are probably of different origins and interpreted as limbidia in F. javanicus but not in F. nobilis. In F. jungermannioides, Wongkuna et al. (2009) interpreted the bands as partially or incompletely differentiated limbidia, which we also agree because of its oblique and elongated

47 Figure 4. Fissidens jungermannioides Griff. A: Habit. B–C: Plants. D–F: Leaves. G: Transverse section of stem. H–K: Transverse sections of leaf. L: Leaf apex. M: Mid leaf. N: Leaf base. All figures taken from Tang & Wei 20200422-1.

48 cells. However, unlike the interrupted band described in Wongkuna et al. (2009), the bands in the dorsal and apical laminae in our material are continuous without breaks while disappearing near the leaf apex. Although paler segments along the bands can be observed from the planar view (e.g. Fig. 4D–F), examination of sequential transverse-sections along parts of a same leaf has revealed that the band is in fact continuous with at least 2-cell thickness. However, the intensity of cell-wall thickenings and cell size may differ along the band, where segments with larger cells and weaker wall thickenings appear paler, giving a false impression of discontinuity. Thus, we concluded that the bands, at least in our material, are continuous but unevenly thickened. In addition, these bands on vaginant laminae in our material are also observed to be weak to absent. We consider all these differences as minor variations within the species.

5. Fissidens kinabaluensis Z.Iwats., J. Hattori Bot. Lab. 32: 269. 1969. Fig. 5 This species is characterised by 1) small plants (2.0–3.5 mm tall) and simple stems, 2) well-differentiated axillary hyaline nodules, 3) linear-lanceolate and densely imbricated leaves with shortly excurrent costa, 4) limbidia differentiated along the entire margin of vaginant laminae, 5) pluripapillose laminal cells, 6) rhizautoicous inflorescence, female inflorescences at base of female stems or in axils of lower leaves, and much smaller perichaetial leaves than vegetative ones, 7) erect and symmetrical capsules, and 8) Fissidens-type peristome teeth. Specimen examined: CHINA. Guangxi: Shangsi Co., Shiwandashan National Forest Park, 21°54′21″–21°53′23″N, 107°54′13″–107°54′34″E, 273–450 m elev., on soil, 14 September 2019, He & Tang 49549 (IBK, MO). Distribution: China [Guangdong, Guizhou, Hong Hong, Yunnan (Jia 2018), Taiwan (Chiang et al. 2001), new to Guangxi], Indonesia, Malaysia, Papua New Guinea, Thailand, Vietnam (Eddy 1988; Tan & Ninh 2003; Tan et al. 2006a). Notes: Fissidens kinabaluensis may be confused with F. wichurae, which also has linear- lanceolate leaves and pluripapillose laminal cells, but differs in having weak axillary hyaline nodules, shorter limbidia restricted to lower half of vaginant lamina, terminal perichaetia, and perichaetial leaves that are about as long as the vegetative leaves.

6. *Fissidens laxitextus Broth. ex Gangulee, Nova Hedwigia 8: 144. 1964. Fig. 6 Plants 3–5 mm tall, light green to dark green, growing in short and dense tufts. Stems simple or branched; axillary hyaline nodules not differentiated; cortical cells in cross section small, thick-walled, central strand weakly differentiated. Leaves in sterile stem 8–10 pairs, in fertile stem 4–6 pairs; upper to middle leaves imbricate to contiguous, oblong ovate, 0.7–1.1 mm long, 0.23–0.31 mm wide, lower leaves gradually decreasing in size towards the stem base, distant, broadly acute at apex; base of dorsal lamina rounded; costa ending 2–5 cells below leaf apex, Bryoides-type; margins serrulate throughout; vaginant lamina about 1/2 of leaf length, unequal; laminae unistratose; cells of apical lamina irregularly quadrate to hexagonal, 10–20 µm long, smooth, thin walled. Dioicous; perichaetia terminal; perigonia and sporophytes not seen. Representative specimens examined: CHINA. Guangxi: Leye Co., Yachang Orchid National Nature Reserve, 24°45′32.80″N, 106°21′50.94″E, 1,483 m elev., on soil, 3 October

49 Figure 5. Fissidens kinabaluensis Z.Iwats. A–B: Habits. C: Plant. D–H: Leaves. I: Portion of stem with leaves removed, showing well-differentiated axillary hyaline nodules. J: Lower part of leaf. K: Distal part of vaginant laminae. L: Basal part of vaginant lamina. M: Leaf apex. N– O: Transverse sections of leaf. P: Peristome teeth. Q: Transverse section of stem. R: Exothecial cells. All figures taken from He & Tang 49549.

50 Figure 6. Fissidens laxitextus Broth. ex Gangulee. A: Habit. B–C: Plants. D–G: Leaves. H: Transverse section of leaf. I: Leaf apex. J: Leaf base. K: Cells of apical lamina. L: Transverse section of stem. M–N: Perichaetial leaves. All figures taken from Tang & Zhang 20181003-403.

51 2018, Tang & Zhang 20181003-403 (IBK); Gongcheng Co., Danbaichong Tun, Yindianshan Nature Reserve, 24°53′28.11″N, 111°0′17.6″E, 1,387 m elev., on wet soil., 14 April 2020, Tang 20200414-48 (IBK). Distribution: India, Japan, Nepal (Pradhan & Joshi 2006; Suzuki & Iwatsuki 2012), new to China (Guangxi). Notes: Fissidens laxitextus is recognised by 1) non-differentiated axillary hyaline nodules, 2) oblong-ovate leaves, 3) costa ending below leaf apex, 4) serrulate margins throughout, and 5) smooth and thin walled apical laminal cells. This species is similar to F. pellucidus Hornsch. and F. guangdongensis Z.Iwats. & Z.H.Li, and an excellent discussion on their differences has already been provided in Suzuki & Iwatsuki (2012).

7. *Fissidens pseudoclosteri Z.Iwats. & S.S.Kumar, Hikobia 11: 133. 1992. Fig. 7 Plant minute, 0.40–0.75 mm long, light green to dark green, scattered on soil; protonema not persistent. Stems simple; cortical cells in cross section more or less large, moderately thick-walled, central strand not differentiated. Leaves small, 1–3 pairs; upper leaves larger than lower leaves, 0.4–0.7 mm long, from broad sheathing base abruptly narrowed into a serrulate awn; dorsal lamina none or poorly differentiated; costa weak below, stronger above, excurrent, Thorsbornei-type; margin irregularly serrulate by projecting cells; laminae unistratose; cells of apical lamina irregularly quadrate, rectangular to rhomboidal, 8–21 µm long, smooth, thin walled, cells at upper portion of vaginant lamina short rectangular in margin, 10–15 µm long, gradually larger toward costa, 13–35 µm long, cells at base rectangular, large, 25–40 µm long. Rhizautoicous; perigonia at base of stem; seta terminal, 2–3 mm long; capsule erect, symmetrical; urn ovoid, 0.4–0.55 mm long; exothecial cells rectangular with thickened longitudinal walls; peristome teeth Fissidens-type; spores 8–12 µm, smooth; calyptra and operculum not seen. Representative specimens examined: CHINA. Guangxi: Leye Co., Yanglin Village, Dacao Tun, out of Meiguidong Cave, 24°47′36.32″N, 106°30′39.00″E, 1,100 m elev., on rock, 16 April 2018, Tang 20180416-758B (IBK); Shuaba Village, Leirong Tun, Liuxing Tiankeng, 24°48′40.47″N, 106°28′40.40″E, 1,142 m elev., on soil, 8 June 2018, Tang 20180608-109 (IBK). Distribution: India (Iwatsuki & Kumar 1992), Japan (Suzuki & Iwatsuki 2012), new to China (Guangxi). Notes: Fissidens pseudoclosteri is readily distinguished in the genus by its 1) minute, bud-like plants, 2) absence of dorsal lamina, 3) excurrent costae, and 4) rectangular exothecial cells with thickened longitudinal walls. Because of its minuscule size, F. pseudoclosteri is easily overlooked in the field. From the point of ontogeny, F. pseudoclosteri and related species (used to be treated as a separate genus Nanobryum Dixon) can be interpreted as neotenic with absent to weak development of dorsal and apical laminae in their leaves (Pursell & Reese 1980). In general, the first few leaves of a new shoot in Fissidens are small, scale-like, and may consist of only a costa and a pair of vaginant laminae. In successive leaves, dorsal and apical laminae are gradually developed (Mishler 1988). This explain very well the variation seen in the development of the dorsal lamina in F. pseudoclosteri. It is completely absent in the type

52 Figure 7. Fissidens pseudoclosteri Z.Iwats. & S.S.Kumar. A: Habit of plants (tiny plants with sporophytes) mixed with F. serratus (right foreground light green vegetative shoots) and F. bryoides (background larger shoots). B: Close-up. C–D: Plants. E–G, L: Leaves. H: Distal part of “vaginant lamina”. I: Basal leaf cells. J: Transverse section of stem. K: Exothecial cells. M–N: Transverse sections of leaf. All figures taken from Tang & Wei 20191012-64.

53 material from India, usually absent but occasionally weakly developed (see Fig. 7G) in Chinese plants, and often poorly developed in Japanese plants (Suzuki & Iwatsuki 2012). Fissidens takayukii Tad.Suzuki, a Japanese endemic (Suzuki 2015) described as without differentiated “vaginant laminae”, appears remarkably close to F. pseudoclosteri. We found no difference between the vaginant laminae of F. pseudoclosteri and that of F. takayukii. Both species are also similar in having a poorly differentiated costa in the lower half of the leaves. The only difference we could decipher is in the costa that is percurrent in F. takayukii and excurrent in F. pseudoclosteri. The molecular phylogenetic study of Suzuki et al. (2018) derived from rbcL and rps4 data has supported the two as the closest related species among sampled species. Combining both the morphological and genetic similarities, the two species can be concluded to be closely related. However future studies are necessary to interpret if they are distinct or representing variations of a single species.

8. Fissidens serratus Müll.Hal., Bot. Zeitung (Berlin) 5: 804. 1847. Fig. 8 This species is characterised by 1) small plants (0.7–1.7 mm tall) and simple stems, 2) weakly differentiated axillary hyaline nodules, 3) lanceolate leaves with subpercurrent to percurrent costa, 4) serrulate leaf margins, 5) laminal cells with a central papilla, 6) rhizautoicous or autoicous inflorescence (Iwatsuki & Suzuki 1982), 7) erect and symmetrical capsules, and 8) Fissidens-type peristome teeth. Specimens examined: CHINA. Guangxi: Leye Co., Yachang Orchid National Nature Reserve, 24°50′52.93″N, 106°24′59.50″E, 1,060 m elev., on soil, 8 October 2018, Tang & Zhang 20181008-613B (IBK); 24°48′04.98″N, 106°21′46.54″E, 1,091 m elev., on soil, 20 October 2019, Tang & Wei 20191020-490 (IBK). Distribution: Pantropical, occurring also in Australia and New Zealand (Li & Iwatsuki 2001). In China, previously recorded from Guizhou, Hainan, Hong Kong, Shandong, Taiwan (Jia 2018), new to Guangxi. Notes: Fissidens serratus is easily confused with F. flabellulus. Differences are discussed under the latter species.

9. Fissidens subangustus M.Fleisch., Musci Buitenzorg 1: 47. 1904. Fig. 9 This species is characterised by 1) medium-sized plants (4–6 mm tall), 2) usually zigzag stem (Fig. 9G), 3) well-differentiated axillary hyaline nodules, 4) narrowly lanceolate leaves with subpercurrent to percurrent costa, 5) weakly differentiated limbidia restricted to the vaginant lamina of perichaetial leaves (Iwatsuki & Suzuki 1982), 6) pluripapillose laminal cells, and 7) dioicous inflorescence (Iwatsuki & Suzuki 1982). Specimen examined: CHINA. Guangxi: Yongfu Co. Luojin Town, Qianlong Tiankeng, 24°58′03.93″N, 110°08′51.02″E, 277 m elev., on soil., 20 August 2019, Tang, Huang & Shen 20190820-8 (IBK). Distribution: China [Guizhou, Hunan, Taiwan (Jia 2018), new to Guangxi], Indonesia, Japan, Philippines, Thailand (Iwatsuki & Tan 1980; Iwatsuki & Suzuki 1982; He 1998 –2020). Notes: Morphologically, F. subangustus may be confused with F. crispulus Brid. owing to zigzag-appearance of the stem when leaves are removed and the presence of distinct axillary hyaline nodules. However, laminal cells of F. crispulus are distinctly mammillose.

54 Figure 8. Fissidens serratus Müll.Hal. A: Habit. B: Plant. C–D: Leaves. E: Perichaetial leaf. F–G: Transverse sections of leaf. H: Leaf apex. I: Leaf base. J: Capsule. K: Distal part of vaginant laminae. L: Portion of stem with leaves removed, showing weakly differentiated axillary hyaline nodules. M: Transverse section of stem. All figures taken from Tang & Wei 20191020-490.

55 Figure 9. Fissidens subangustus M.Fleisch. A: Habit. B: Plant. C–F: Leaves. G: Portion of stem, right-side leaves removed to show the characteristic zigzag and the well-differentiated axillary hyaline nodules. H: Leaf apex. I: Distal part of vaginant laminae. J: Transverse section of leaf. K: Transverse section of stem through a hyaline nodule. All figures taken from Tang et al. 20190820-8.

56 Figure 10. Fissidens wichurae Broth. & M.Fleisch. A: Habit. B: Plant. C–F: Leaves. G: Perichaetial leaf. H–J: Transverse sections of leaf. K: Portion of stem, right side leaves removed to show the weakly differentiated axillary hyaline nodules. L: Leaf apex. M: Transverse section of stem. N: Median leaf cells. O: Peristome teeth. P: Exothecial cells. All figures taken from Tang 20180112-63.

57 10. Fissidens wichurae Broth. & M.Fleisch., Hedwigia 38: 127. 1899. Fig. 10 This species is characterised by 1) small plants (1.5–3.0 mm tall) and simple stems, 2) weakly differentiated axillary hyaline nodules, 3) linear-lanceolate and imbricate leaves with excurrent costa, 4) limbidia distinctly differentiated along margins of lower half of vaginant lamina in most leaves, 5) pluripapillose laminal cells, 6) rhizautoicous inflorescence (Suzuki & Iwatsuki 2012), 7) erect and symmetrical capsules, and 8) Fissidens-type peristome teeth. Specimen examined: CHINA. Guangxi: Daxin Co., Encheng National Nature Reserve, 22°47′25.36″N, 107°03′50.82″E, 299 m elev., on rotten log, 12 January 2018, Tang 20180112-63 (IBK). Distribution: China [Guangdong, Hainan, Hong Kong, Taiwan, Yunnan (Jia 2018), new to Guangxi], Indonesia, Japan, Malaysia, Papua New Guinea, Thailand, Vietnam (Touw 1968; He & Khang 2012; Suzuki & Iwatsuki 2012). Notes: Fissidens wichurae is easily confused with F. linearis var. obscurirete (Broth. & Paris) I.G.Stone, and sometimes it is difficult to separate them. However, in the latter, limbidia are found only on the vaginant laminae of the upper and perichaetial leaves. Fissidens wichurae is also closely related to F. kinabaluensis. Differences between the two are given under the latter species.

Acknowledgements Sincere thanks are given to Dr. Si He (from the Missouri Botanical Garden, MO), Ping Huang, Yun-Biao Liao, Chao Shen, and Shi-Yan Zhang who have kindly assisted us during fieldwork. We are also grateful to the Administration of Leye National Geopark, Dayaoshan National Nature Reserve, Encheng National Nature Reserve, Yachang Orchid National Nature Reserve, Shiwandashan National Nature Reserve, and Yindianshan Nature Reserve for their kind help during the field trips. We thank two anonymous reviewers for their suggestions. This research was sponsored by the National Natural Science Foundation of China (no. 31960045) and the Project of Fundamental Research of Guangxi Academy of Sciences (no. 2018YJJ907).

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