$¢PhytoKeys PhytoKeys 259: 145-160 (2025) DOI: 10.3897/phytokeys.259.156710 Research Article The genus Pycnolejeunea (Lejeuneaceae, Marchantiophyta) in Thailand, with the description of Pycnolejeunea zhuiana Chatchaba Promma’™, Sahut Chantanaorrapint'® 1 PSU-Herbarium, Division of Biological Science, Faculty of Science, Prince of Songkla University, Hat Yai, Songkhla 90110, Thailand Corresponding author: Sahut Chantanaorrapint (sahut.c@psu.ac.th) OPEN @ ACCESS Academic editor: Matthew Renner Received: 23 April 2025 Accepted: 11 June 2025 Published: 1 July 2025 Citation: Promma C, Chantanaorrapint S (2025) The genus Pycnolejeunea (Lejeuneaceae, Marchantiophyta) in Thailand, with the description of Pycnolejeunea zhulana. PhytoKeys 259: 145-160. https://doi. org/10.3897/phytokeys.259.156710 Copyright: © Chatchaba Promma & Sahut Chantanaorrapint. This is an open access article distributed under terms of the Creative Commons Attribution License (Attribution 4.0 International - CC BY 4.0). Abstract A taxonomic study of the genus Pycnolejeunea in Thailand is presented, based on herbarium specimens and new collections from field surveys. Three species are recognised including P contigua, P. grandiocellata and one new species, P zhuiana. The new species is distinguished by the strongly papillose lobules, the presence of 1-8 basal ocelli on the lateral leaf and male bracteoles occurring along nearly the whole of the androecial branch length. A key to species, descriptions and illustrations are provided; ecology and geographical distribution of the species are also described. Key words: Endemic species, leafy liverwort, ocellus, Peninsular Thailand, subtribe Pycnolejeuneinae Introduction The genus Pycnolejeunea (Spruce) Schiffn. was originally described by Spruce (1884) as a subgenus of Lejeunea Libert. and was raised to generic rank by Schiffner (1893). The genus Pycnolejeunea was monographed by He (1999), who accepted nine species worldwide. In the world checklist of horn- worts and liverworts (S6derstr6m et al. 2016), 21 species were accepted, in- cluding seven doubtful species. Subsequently, three additional species were described (Bastos and Zartman 2017; Reiner-Drehwald and Gradstein 2018; Thouvenot and Gradstein 2021), increasing the total number of species to 24. Pycnolejeunea is a pantropical genus, with the greatest diversity found in the Neotropics, where ten species are known to occur (Reiner-Drehwald and Gradstein 2018; Bastos et al. 2020). Species of Pycnolejeunea are cor- ticolous epiphytes growing on tree trunks and twigs in tropical lowland and submontane rainforests. Pycnolejeunea can be recognised by the follow- ing morphological characteristics: 1) rigid stems composed of thick-walled cells; 2) imbricate and convex leaf lobes; 3) leaf lobe cells being mammil- lose or papillose, rarely plane, with distinct and rather large trigones; 4) the presence of ocelli in leaf lobes and female bracts; 5) large coarsely granular oil bodies; 6) lobules featuring a well-developed first tooth with a marginal hyaline papilla; 7) gynoecia with pycnolejeuneoid innovations and 8) peri- anths with five smooth to slightly crenate keels. Pycnolejeunea might be 145 Chatchaba Promma & Sahut Chantanaorrapint: The genus Pycnolejeunea (Lejeuneaceae, Marchantiophyta) in Thailand easily confused with Cheilolejeunea (Spruce) Steph. in general appearance. However, Cheilolejeunea is distinguished by the elaborated second tooth, which causes the papilla to appear distal (in Pycnolejeunea, the second tooth is small compared to the first tooth and the papilla appears proximal) and usual lack of ocelli (Gradstein 2021). In Thailand, Pycnolejeunea was first documented by Stephani (1902), who described a new species, Pycnolejeunea grandiocellata Steph., from Koh Chang, Trat Province. More than 100 years later, P contigua (Nees) Grolle was reported from coastal sand dune forest, Phang Nga Province (Suwan- mala and Chantanaorrapint 2016). More recently, Senayai et al. (2020) discovered three Pycnolejeunea species including: P contigua, P. grandio- cellata and P. cavistipula (Steph.) Mizut. from Khao Ngon Nak Mountain, Hat Noppharat Thara - Mu Ko Phi Phi National Park, Krabi Province. After re-examination of the specimens of P cavistipula, they were misidentified and resemble P. papillosa X.-L. He from tropical America in having papillose lobules (He 1999). Following a detailed comparison with closely-related taxa, we here describe these specimens as a new species. The aim of the present study was to revise the genus Pycnolejeunea in preparation for the Bryophyte flora of Thailand. Materials and methods This study is based on recent collections from Thailand as well as herbarium specimens housed in BKF, EGR and PSU. Morphological and anatomical char- acters were studied using stereo- and compound microscopes. The distinctive characters of the species were photographed by an Olympus BX51 light mi- croscope with attached Olympus DP74 Microscope Digital Camera and illus- trated with Nikon Eclipse E200 with attached Nikon Y-IDT Drawing Tube after fully rehydrating samples with tap water. The distinctive characters of the new species were examined and photographed by an FEI Quanta 400 scanning elec- tron microscope. Voucher specimens of the new species are deposited in BKF, NICH and PSU Herbaria. Descriptions, illustrations and a key to species of the genus Pycnolejeunea in Thailand are provided. In addition, distribution and eco- logical data were compiled. Taxonomic treatments Key to species of the genus Pycnolejeunea in Thailand 1 Lobule cells strongly papillose; leaf cells strongly mammillose on the dor- Bal SIGs cc Sececneiowutt. abr. due nc, beseeehe re be tee tee cree ioe eb onuustem ev dTset P. zhuiana - Lobule cells nearly smooth or slightly convex; leaf cells slightly convex or weakly mammillose on the dorsal Side@ ................ccccecessseceesteeceseeeeeseseeeeeeees 2 2 Ocelli suprabasal, mostly 4-15 per leaf lobe, commonly aggregated; lobule oblong to rectangular; plants without flagelliform shoots ................ Wee ete seein tos wu cucties gheaibns seauun ams Paumitae toca face etteabloosuatet sae tausne P. grandiocellata - Ocelli basal, mostly 1-5 per leaf lobe, isolated or aggregated; lobule ovate; plants usually with flagelliform ShOOtS ............cccccceceseceeseeeereees P. contigua PhytoKeys 259: 145-160 (2025), DOI: 10.3897/phytokeys.259.156710 146 Chatchaba Promma & Sahut Chantanaorrapint: The genus Pycnolejeunea (Lejeuneaceae, Marchantiophyta) in Thailand 1. Pycnolejeunea contigua (Nees) Grolle, J. Hattori Bot. Lab. 45: 179. 1979. Figs<1,2 = Jungermannia contigua Nees in Martius, FI. Brasil. enum. plant.1(2): 360. 1833. Type: BRAZIL. Para: ad corticem arborum, C.F. Martius s.n. (isotype: G [G00128260)). = Pycnolejeunea bancana Steph., Hedwigia 35: 124. 1896. Type: INDONESIA. In- sula Banca, 1883, J.E. Teysmann s.n. (lectotype: G [G00281813], designated by He (1999)). = Pycnolejeunea papulosa Steph., Hedwigia 35: 125. 1896. Type: BRAZIL. Para: Caripi, R. Spruce s.n. (lectotype: G [G00128263], designated by Grolle (1979); isolectotypes: G [G00128261, G00128262], JE, M, W). = Pycnolejeunea densiuscula Spruce ex Steph., Sp. Hepat. 5: 613. 1914. Type: BRAZIL. Para: Silva Amazonica, Santarém, Dec 1849, R. Spruce s.n. (lectotype: G [G00128259] designated by Grolle (1979); isotype: G [600128258], JE, M). = Pycnolejeunea ocellata Steph., Sp. Hepat. 5: 614. 1914. Type: CUBA. C. Wright s.n. (lectotype: G [G00128226], designated by He (1999); isolectotype: JE [JE04002710)). Description. Plants whitish-green or light green when fresh, yellowish-brown or light brown in dry condition; shoots 0.9-1.5 mm wide, usually scarce- ly and irregularly branched; branches Lejeunea-type. Stems 100-130 um diameter, in transverse section with 9(-10) epidermal cells, surrounding 14-18 medullary cells, epidermal cells larger than medullary cells; cell walls pale brown or yellowish-brown, thick-walled, with triangular to bulging trigones, wall between trigones with thin to rather thick continuous thick- enings; ventral merophyte 2 cells wide. Rhizoids at base of underleaves, few, tufted, usually hyaline, rhizoid disc not seen. Leaves closely imbricate, when moist, wide-spreading. Leaf lobes ovate to oblong-ovate, rarely fal- cate-ovate, 725-827 um long, 544-617 um wide, dorsal margin arched, ven- tral margin arched, margin entire to slightly crenulate with projecting cells, apex rounded, incurved. Lobe cells convex or weakly mammillose on dorsal side, thin-walled, with small to large triangular trigones, intermediate thick- enings absent or occasionally seen in the basal cells; marginal cells rect- angular or quadrate, 16.5-20.8 x 15.0-23.7 um; median cells hexagonal to rounded, 22.5-37.0 x 21.5-38.5 um, basal cells hexagonal to rectangular, 22.0-45.8 x 20.0-30.0 um; ocelli rectangular to long hexagonal, 47-65 x 25-40 um, (0O-)1—5 per leaf lobe, basal, aggregated or isolated; oil bodies 3-5 per cell, long ellipsoidal to ovoid-cylindrical, 10.4-19.8 x 3.7-5.1 um, Calypogeia-type, coarsely granular. Lobules small, ovate, 152-182 um long, 120-135 um wide, inflated, 0.2-0.3 of lobe length, free margin slightly in- volute, formed by 5-7 elongated cells, apex semicircular, apical tooth short, 1-celled, obtuse, keel arched or nearly straight, lobule cells smooth or slightly convex. Underleaves imbricate, rarely contiguous, suborbicular to reniform, 287-330 um long, 416-458 um wide, wider than long, 3-5 of stem width, bifid to 1/2 of its length, lobes triangular with acute to obtuse apex, margin nearly entire or bluntly toothed at side, sinus V-shaped, bases rounded to cu- neate, insertion line arched. Asexual reproduction by unmodified caducous PhytoKeys 259: 145-160 (2025), DOI: 10.3897/phytokeys.259.156710 147 Chatchaba Promma & Sahut Chantanaorrapint: The genus Pycnolejeunea (Lejeuneaceae, Marchantiophyta) in Thailand Wox 3) Yar LC ¢: i « tt Ct EN SS oF ra ttt cm tea ro SI S ( ea €: aS NY SA ts. Waa Figure 1. Pycnolejeunea contigua (Nees) Grolle. A. Portion of sterile plant, ventral view; B. Portion of sterile plant with flagelliform shoot, ventral view; C. Transverse section of stem; D-F. Lateral leaves; G. Cells from basal and near middle portion of leaf, dorsal view; H. Cells from apical leaf margin; I. Leaf lobule; J-M. Underleaves. Drawn by C. Promma; based on C. Promma & K. Chanakarn 20250215-28B (PSU). leaves, lobules remain attached to the stem; or modified caducous leaves arising from upright flagelliform shoots on branch apices, smaller than or- dinary leaves, margins usually with 1-celled rhizoids. Sexuality autoicous. Androecia, gynoecia and sporophytes not seen. PhytoKeys 259: 145-160 (2025), DOI: 10.3897/phytokeys.259.156710 148 Chatchaba Promma & Sahut Chantanaorrapint: The genus Pycnolejeunea (Lejeuneaceae, Marchantiophyta) in Thailand —S PRES 38, 9 ~ Figure 2. Pycnolejeunea contigua (Nees) Grolle. A. Portion of sterile plant, ventral view; B. Portion of sterile plant with flagelliform shoot, ventral view; C. Flagelliform shoot; D. Portion of sterile plant, showing underleaves; E. Underleaf; F. Lateral leaf; G. Leaf lobule; H. Transverse section of leaf; I. Transverse section of stem; J-M. Cells from basal portion of leaf, showing ocelli. Photographed by C. Promma; based on C. Promma & K. Chanakarn 2025021 5-28B (PSU). Distribution, habitat and ecology. Pantropical (He 1999; Bastos et al. 2020). In Thailand, Pycnolejeunea contigua was found on tree trunks and branches in forest gaps, along forest margins or open habitats in coastal sand dune and tropical lowland forests, ranging from sea level to 480 m above sea level. PhytoKeys 259: 145-160 (2025), DOI: 10.3897/phytokeys.259.156710 149 Chatchaba Promma & Sahut Chantanaorrapint: The genus Pycnolejeunea (Lejeuneaceae, Marchantiophyta) in Thailand Taxonomic notes. Pycnolejeunea contigua is a widely distributed species distinguished by its pale to glossy brownish plants, 1-5 basal ocelli per leaf lobe (aggregated or isolated) and large broadly ovate to reniform underleaves that almost completely cover the lobules. Asexual reproduction occurs via un- modified caducous leaves with lobules remaining attached to the stem and usually by modified caducous leaves arising from flagelliform shoots. In Thailand, P contigua is most similar to P grandiocellata, sharing several vegetative features such as ovate to oblong leaf lobes, 2-celled wide ventral merophytes and smooth to slightly convex lobule cells. However, P contigua differs in having 1-5 ocelli which are basal in position, whereas P. grandiocella- ta exhibits more ocelli (4-15) suprabasal ocelli commonly aggregated from the base to the ventral half of the lobe. Additionally, the presence of modified ca- ducous leaves (flagelliform shoots) in P contigua further distinguishes it from P grandiocellata, which produces only unmodified caducous leaves. Specimens examined. THAILAND. Phang Nga: Hat Thai Mueang - Khao Lampi National Park, 8°29.1523'N, 98°13.6872'E, 18 m elev., 10 Oct 2015, O. Suwan- mala 111, 119A (PSU); 8°29.011'N, 98°13.7605'E, 13 m elev., 30 Jan 2016, O. Suwanmala 186 (PSU); Krabi: Hat Noppharat Thara - Mu Ko Phi Phi National Park, Khao Ngon Nak Mountain, 8°5.2767'N, 98°46.47'E, 480 m elev., 24 Mar 2018, A. Senayai 75a, 126b (BKF, PSU); 12 Oct 2018, A. Senayai 212 (BKF, PSU); 8°5.2767'N, 98°46.47'E, 480 m elev., 15 Feb 2025; C. Promma & K. Chanakarn 20250215-19, 20250215-28B (PSU); Yala: Betong, Ban Piyamit 2, 14 Jun 2013, S. Chantanaorrapint & C. Promma 2515 (PSU). 2. Pycnolejeunea grandiocellata Steph. in Schmidt, Fl. Koh Chang, Bot. Tidsskr. 24: 279. 1902. Figs 3,4 Type material. THAILAND. Trat: Klong Munse, 1899-1900, E. J. Schmidt 6 (holo- type: G [G00128271)). Description. Plants whitish-green or light green when fresh, yellow- ish-brown or light brown in dry condition; shoots 0.80-1.23 mm wide, usual- ly scarcely and irregularly branched; branches Lejeunea-type. Stems 76-99 um diameter, in transverse section with 8-11 epidermal cells, surround- ing 9-14 medullary cells, epidermal cells larger than medullary cells; cell walls pale brown or yellowish-brown, thick-walled, with triangular to bulging trigones, wall between trigones with thin to rather thick continuous thicken- ings; ventral merophyte 2 cells wide. Rhizoids at base of underleaves, few, tufted, usually hyaline, rhizoid disc not seen. Leaves imbricate, wide-spread- ing when moist. Leaf lobes ovate, oblong-ovate to oblong, 468-680 um long, 376-487 um wide, dorsal margin broadly arched, ventral margin slightly to strongly arched, margin entire, apex rounded, incurved. Lobe cells convex or weakly mammillose on dorsal side, thin-walled, with small to large triangular trigones, intermediate thickenings absent or occasionally seen in the mar- ginal and basal cells; marginal cells rectangular or quadrate, 18.0-22.8 x 11.3-23.0 um, median cells hexagonal to rounded, 18.0-38.3 x 19-24.8 um, basal cells hexagonal to rectangular, 25.0-41.5 x 20.0-26.0 um; ocelli rect- angular to long hexagonal, 39.5-63.5 x 21.0-36.5 um, 4-15 per leaf lobe, PhytoKeys 259: 145-160 (2025), DOI: 10.3897/phytokeys.259.156710 150 Chatchaba Promma & Sahut Chantanaorrapint: The genus Pycnolejeunea (Lejeuneaceae, Marchantiophyta) in Thailand Figure 3. Pycnolejeunea grandiocellata Steph. A. Portion of sterile plant, ventral view; B. Portion of fertile plant, ventral view; C, D. Transverse sections of stems; E-H. Lateral leaves; I. Cells from basal and near middle portion of leaf, dorsal view; J. Cells from apical leaf margin; K. Leaf lobule; L-O. Underleaves; P. Androecium; Q. Gynoecium; R. Perianth; S, T. Female bracts; U. Female bracteole. Drawn by C. Promma; based on T. Pécs & S. Somadee 1227/K (PSU). suprabasal, commonly aggregated, confined from base to the ventral half of leaf lobe; oil bodies not seen. Lobules small, oblong, 132-178 um long, 90-109 um wide, inflated, 0.16-0.30 of lobe length, free margin slightly involute, formed by 5-7(-9) elongated cells, apex semicircular or rarely PhytoKeys 259: 145-160 (2025), DOI: 10.3897/phytokeys.259.156710 151 Chatchaba Promma & Sahut Chantanaorrapint: The genus Pycnolejeunea (Lejeuneaceae, Marchantiophyta) in Thailand Kt re: Pr. , fs iy r = é\ ¥ > h. > {) {7 ‘| r «| y Figure 5. Pycnolejeunea zhuiana Promma & Chantanaorr. sp. nov. A. Portion of sterile plant, ventral view; B. Portion of fertile plant, ventral view; C. Transverse sections of stem; D-G. Lateral leaves; H. Cells from basal and near middle portion of leaf, dorsal view; I. Cells from apical leaf margin; J-L. Leaf lobules; L. Leaf lobule from inner side with hyaline papilla; M—O. Underleaves; P, Q. Androecia; R. Gynoecium; S. Perianth; T, U. Female bracts; V. Female bracteole. Drawn by C. Promma; based on C. Promma & K. Chanakarn 20250215-30 (PSU). PhytoKeys 259: 145-160 (2025), DOI: 10.3897/phytokeys.259.156710 154 Chatchaba Promma & Sahut Chantanaorrapint: The genus Pycnolejeunea (Lejeuneaceae, Marchantiophyta) in Thailand Diagnosis. Pycnolejeunea zhuiana similar to P. papillosa, but differs in having 1-8 ocelli per leaf lobe, stems in transverse section composed of 9-11 epider- mal cells surrounding 13-15 medullary cells and male bracteoles occurring along nearly the whole of the androecial branch length. Description. Plants whitish-green or light green when fresh, yellowish-brown or light brown in dry condition; shoots with leaves 0.71-1.32 mm wide; usu- ally scarcely and irregularly branched; branches Lejeunea-type. Stems 117- 132 um diameter, in transverse section with 9-11 epidermal cells, surrounding 13-15 medullary cells, epidermal cells larger than medullary cells; cell walls pale brown or yellowish-brown, thick-walled, with triangular to bulging trigones, wall between trigones with thin to rather thick continuous thickenings; ventral merophyte 2 cells wide. Rhizoids at base of underleaves, few, tufted, usually hyaline, rhizoid disc not seen. Leaves imbricate, wide-spreading when moist. Leaf lobes ovate to oblong-ovate, occasionally falcate-ovate, 563-698 um long, 429-512 um wide, dorsal margin broadly arched, ventral margin slight- ly to strongly arched, margin entire or conspicuously crenulate with projecting cells, apex rounded, incurved. Lobe cells strongly mammillose on dorsal side, thin-walled, with small to large triangular trigones, intermediate thickenings ab- sent or occasionally seen in the basal cells; marginal cells rectangular or quad- rate, 12.5-20.5 x 12-18 um, median cells hexagonal to rounded, 20.5-34.0 x 19.0-27.5 um, basal cells hexagonal to rectangular, 22.0-42.6 x 20.0-30.5 um; ocelli rectangular to long hexagonal, 35.0-61.7 x 23.6-36.0 um, 1-8 per leaf lobe, basal, aggregated or isolated; oil bodies 2-5 per cell, long ellipsoidal to ovoid-cylindrical, 7.0-19.0 x 4.0-7.0 um, Calypogeia-type, coarsely granular. Lobule small, ovate, 138-170 um long, 125-156 um wide, strongly inflated, 0.20-0.25 of lobe length, free margin slightly involute, formed by 5-6 elongated cells, apex semicircular, apical tooth short, obtuse; keel strongly arched, papil- lose; lobule cells strongly unipapillose. Underleaves contiguous to imbricate, sometimes slightly remote, suborbicular to subreniform, 234-316 um long, 257-360 um wide, wider than long, 3.0-3.5 of stem width, bifid to 1/3-1/2 of its length, lobes triangular with acute to obtuse apex, margin nearly entire, rarely bluntly toothed at side, sinus V-shaped, bases rounded to cuneate, insertion line arched. Asexual reproduction by unmodified caducous leaves, lobules remain attached to the stem. Sexuality autoicous. Androecia on short branches, ter- minal or intercalary on branches, inflated, spicate, 515-913 um long, 408-561 um wide; bracts in 3-5 pairs, densely imbricate, isolobous; bracteoles occurring nearly throughout androecium, composed of 2(—3) bilobed bracteoles restrict- ed at the base of the branch and 1-2 reduced once above. Gynoecia on short branches, with 1 subfloral innovation; bracts in one pair, subequal in size, bract lobe obovate, 526-822 um long, 317-488 um wide, apex rounded, incurved, margin entire, ocelli 0-14 per lobe, isolated; bract lobules lingulate, narrowly oblong to ovate, 330-442 um long, 132-258 um wide, 0.6—0.8 of lobe length, ca. 2/3 of the bract-lobe area, apex acute to broadly obtuse, keel slightly arched, short; bracteole shortly connate with the bracts at the base on one side or rarely on both sides, ovate to obovate, 418-587 um long, 276-409 um wide, apex usually emarginate or slightly bifid, lobe acute, margin entire; perianths obovate, ca. 0.5 emergent beyond bracts or sometimes almost entirely covered by bracts, 664-921 um long, 464-624 um wide, inflated, 5-keeled, keels crenulate or rough from projecting cells, apex usually truncate, beak short. Sporophytes not seen. PhytoKeys 259: 145-160 (2025), DOI: 10.3897/phytokeys.259.156710 155 Chatchaba Promma & Sahut Chantanaorrapint: The genus Pycnolejeunea (Lejeuneaceae, Marchantiophyta) in Thailand 50 wm Figure 6. Pycnolejeunea zhuiana Promma & Chantanaorr. sp. nov. A, B. Portions of sterile plants, ventral view; B. Showing underleaves; C. Portion of fertile plant, ventral view; D. Androecium; E. Portions of sterile plants, showing lobule; F. Lateral leaf; G. Leaf lobule; H. Underleaf; I. Perianth; J, K. Female bracts; L. Female bracteole; M-O. Cells from basal portion of leaf, showing ocelli; P. Cells from middle portion of leaf, ventral view; Q. Transverse sections of stem and lobule; R. Trans- verse section of leaf. Photographed by C. Promma; based on C. Promma & K. Chanakarn 20250215-30 (PSU). Etymology. The specific epithet “zhuiana” honours Prof. Dr. Rui-Liang Zhu of East China Normal University, Shanghai (China), who has dedicated his entire life to the study of bryophytes, particularly in the taxonomy and systematics of Lejeuneaceae and the advancement of liverwort research in Asia. PhytoKeys 259: 145-160 (2025), DOI: 10.3897/phytokeys.259.156710 156 Chatchaba Promma & Sahut Chantanaorrapint: The genus Pycnolejeunea (Lejeuneaceae, Marchantiophyta) in Thailand -_ = [| ad —} — Le | 5 Figure 7. Pycnolejeunea zhuiana Promma & Chantanaorr. sp. nov. (SEM). A-C. Portions of sterile plants; A, B. Ventral views; C. Dorsal view; D. Androecium; E. Leaf lobule; F. Cells from middle portion of leaf, dorsal view. Photographed by C. Promma; based on C. Promma & K. Chanakarn 2025021 5-30 (PSU). Distribution, habitat and ecology. Endemic to peninsular Thailand. So far known only from its type locality at Khao Ngon Nak Mountain, Hat Noppharat Thara - Mu Ko Phi Phi National Park, Krabi Province; however, it may also occur in other areas in southern Thailand with a similar vegetation type. Pycnolejeunea zhuiana was found growing on tree trunks in tropical lowland forests dominated by Baeckea frutescens L., Podocarpus neriifolius D.Don. and Syzygium antisep- ticum (Blume) Merr. & L.M. Perry., at elevations of 380-480 m. It is often found growing in association with Lejeunea flava (Sw.) Nees and P. contigua. PhytoKeys 259: 145-160 (2025), DOI: 10.3897/phytokeys.259.156710 157 Chatchaba Promma & Sahut Chantanaorrapint: The genus Pycnolejeunea (Lejeuneaceae, Marchantiophyta) in Thailand Taxonomic notes. Pycnolejeunea zhuiana is readily distinguished by a com- bination of the following characters: ventral merophyte consistently 2 cells wide; oblong-ovate to oblong leaf lobes; strongly mammillose on dorsal side of leaf lobe cells; presence of 1-8 ocelli per leaf lobe which are either aggregated or isolated at the basal region of the lobe; the strongly papillate lobules with 5-6 elongate cells along the free margin; and male bracteoles occurring nearly throughout the androecial branch. Pycnolejeunea zhuiana can be confused with P papillosa from tropical America, which also have papillose lobues and unipapillose leaf cells. However, P zhuiana is distinguished by its larger size and ovate to oblong-ovate leaf lobes, while P papillosa has smaller shoots and orbicular-ovate leaf lobes. Additionally, P zhuiana has 1-8 ocelli per leaf lobe, while P papillosa has only 1-2(-3) ocelli per leaf lobe. Pycnole- jeunea zhuiana also has male bracteoles almost throughout the androecial branch. In contrast, P papillosa has only one male bracteole restricted to the base of the branch. The differences between the two species are shown in Table 1. With regards to the male bracteole, most species of Pycnolejeunea have only 1 or 1-2 bracteoles per androecial branch and restricted to the base of the an- droecium. Except for P macroloba (Nees & Mont.) Schiffn. from the Neotropics, male bracteoles are present throughout the androecium or nearly so (He 1999). However, P macroloba differs from P zhuiana in the larger plant (to 2.5 mm wide), the rectangular lobules (0.5—-0.6 of lobe length) with 9-20 elongated cells along the lateral margin and nearly smooth lobule surface. Additional specimens examined. THAILAND. Krabi: Hat Noppharat Thara - Mu Ko Phi Phi National Park, Khao Ngon Nak Mountain, 8°5.415'N, 98°46.1683'E, 380 m elev., 24 Mar 2018, A. Senayai 64 (BKF, PSU); 8°5.2767'N, 98°46.47'E, A480 m elev., 9 Apr 2022, S. Chantanaorrapint & A. Chantanaorrapint s.n. (PSU); 8°5.2767'N, 98°46.47'E, 480 m elev., 15 Feb 2025, C. Promma & K. Chanakarn 20250215-27, 20250215-28A, 20250215-29, 20250215-31 (PSU). Table 1. Morphological differences between Pycnolejeunea zhuiana and P. papillosa. The characters of P papillosa are taken from the protologues and recent publication (He 1999; Bastos et al. 2020). Characteristic Shoot width Stem in transverse section Leaf lobe shape Number of ocelli per leaf lobe Male bracteoles P. zhuiana P. papillosa 0.71-1.32 mm 0.6-1.0 mm 9-11 epidermal cells, surrounding 13-15 7-9 epidermal cells, surrounding 9-10 medullary cells medullary cells Ovate to oblong-ovate, flat to slightly convex, Orbicular-ovate, strongly convex, apex incurved apex plane +6 1T=2(=3) nearly throughout the androecial branch, only 1, restricted at the base of androecia composed of 2(-3) larger bracteoles at the base and 1-2 smaller bracteoles above Acknowledgements We would like to thank K. Chanakarn for his assistance during fieldwork and the curator and staff of BKF and EGR for allowing us to access the available specimens. We would also like to thank C.J.P Bastos, M.A.M. Renner and R.-L. Zhu for their valuable comments and suggestions to improve the manuscript. PhytoKeys 259: 145-160 (2025), DOI: 10.3897/phytokeys.259.156710 158 Chatchaba Promma & Sahut Chantanaorrapint: The genus Pycnolejeunea (Lejeuneaceae, Marchantiophyta) in Thailand Additional information Conflict of interest The authors have declared that no competing interests exist. Ethical statement No ethical statement was reported. Funding This work was supported by the Prince of Songkla University annual government expen- diture under the Plant Genetic Conservation Project Year 2025 under the Royal initiative of Her Royal Highness Princess Maha Chakri Sirindhorn. Author contributions Conceptualization: SC, CP. Funding acquisition: SC. Writing - original draft: CP. Writing - review and editing: SC. 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