Clarkella nana, the only species of the genus Clarkella, is reported for the first time from Vietnam. The species was discovered on wet rocks of a limestone hill in Son La Province. Detailed photographic illustrations of the studied specimen are provided, along with a summary of the species distribution and its ecological preferences. Typification of the names related to Clarkella is revised, and the name Ophiorrhiza pellucida is lectotypified.

A taxonomic revision of Epirixanthes, the only mycoheterotrophic genus of Polygalaceae, is presented for Vietnam. Two species are recognized, of which E. elongata is known to be widely distributed across tropical Asia and E. kinabaluensis was considered endemic to Malesia prior to our study. Several nomenclatural inconsistencies are resolved for the names related to Epirixanthes. The original spelling of the generic name is confirmed as nomenclaturally correct because of being derived from conventional phonetic variants in Medieval Latin. Morphological descriptions of both Vietnamese species are significantly amended, reflecting novel data on the gross structure of their flowers and on intraspecific variation. For each species, the distinction from its most similar congener is summarized. Extensive illustrations of inflorescences and flowers of both species are provided; the inner structure of the intact flowers is illustrated with 3D images produced using X-ray microtomography.

Being the second largest genus in the subfamily Lamioideae (Lamiaceae), Phlomoides comprises approximately 180 species distributed mainly across Eurasia, with diversity centers in Central Asia, the Iranian Plateau, the Hengduan Mountains, and the Himalayas. Previous phylogenetic studies have expanded Phlomoides to include seven traditionally recognized genera and one section of Phlomis. However, limited taxon sampling and geographical coverage have hindered the establishment of a robust infrageneric classification and left key questions regarding its origin, dispersal, and adaptive evolution across heterogeneous habitats unresolved. In this study, we reconstructed the phylogeny of Phlomoides using whole chloroplast genome data and two nuclear DNA regions (ETS and ITS), based on dense sampling that includes 132 species (73% of the genus). Our dataset comprises 206 chloroplast genomes, 154 of which were newly sequenced. Our major findings are: 1) Phlomoides (as currently defined) is monophyletic and subdivided into six well-supported clades, each exhibiting potential morphological synapomorphies; 2) biogeographical reconstruction suggests that Phlomoides originated in the Hengduan Mountains or Central Asia during the Middle Miocene; 3) pinnatipartite leaves, trichomes on mericarps apex, and tuberous roots are likely associated with drought adaptation; and 4) clades exhibit pronounced ecological niche differentiation, particularly with respect to annual precipitation and temperature range, which may have driven divergence into two major clades. This study provides new insights into the evolutionary dynamics and ecological drivers of plant diversification across Eurasia and highlights adaptive strategies in response to climate change.

A new species, Ilex decapetala , is described and illustrated from central Vietnam. It is distinguished by its female flowers with (8–)9–10(–11) pink petals (mostly 10); such a high floral merism is rare within the genus and, on top of this rarity, no other known species of Ilex combines such a high merism with pink corolla. Phylogenetic analyses, based on three nuclear markers (ITS, ETS and nep GS), place the new species in Ilex sect. Prinifoliae with strong support, where it is sister to a clade comprising I. angulata , I. hainanensis , I. pubescens and I. stewardii . Morphologically, I. decapetala resembles I. stewardii most, but differs in having more numerous flowers in female inflorescences (3–18 vs. 1–5) and a higher merism of corolla and androecium of female flowers (8–11 vs. 6–7). In addition, the new species shows similarity to I. umbellulata , which also occurs in central Vietnam, but the latter is distinguished by white flowers with 4–5 petals and staminodes.

A comprehensive revision of morphology, taxonomy and geographical distribution of Duplipetala hexagona, a species of Gentianaceae, is provided. Earlier believed to be endemic to Thailand, the species is here reported from limestone areas of central Laos, representing the first record of the genus Duplipetala in the country. A number of structural traits of D. hexagona are uncovered or clarified; in particular, the pairs of inflorescence bracts are demonstrated to be perfoliate, and the gynophore is described. The morphological description is supplemented for the first time by analytical photographic illustrations. A full list of the available specimens is included, and the distribution of the species is shown on a map. Delimitation between D. hexagona and D. pentanthera is discussed. Diversity of Gentianaceae in Laos is summarized, and keys for identification of the Laotian genera and species of the family are presented.

The paper continues a series of contributions on the taxonomic diversity of Psychotria in Vietnam. Three species are revised here for the country. Of them, P. hainanensis represents a new national record, and the presence of P. tutcheri in Vietnam is confirmed for the first time by specimen investigation. For P. prainii, two new synonyms, P. rhodotricha and P. thorelii, are proposed. For each species, a morphological description is compiled and taxonomic and nomenclatural notes are given, along with geographical distribution, notes on their ecology and phenology and analytical illustrations. Lectotypes for three names in Psychotria are designated.

Perilimnastes dongchauensis (Melastomataceae), apparently endemic to Quang Tri province, Central Vietnam, is described here as a new species. It closely resembles P. suberalata in having elliptic-lanceolate leaf blades, few-flowered inflorescences, 4-merous flowers, and similar anther morphology. However, it differs in several key characteristics, with stems and petioles densely setose (vs. glabrous), leaves equal or subequal in a pair (vs. unequal, rarely subequal) and adaxial surface setose (vs. glabrous), hypanthia setose (vs. glabrous), calyx lobes narrowly triangular (vs. linear), and petals much larger, measuring 17–20 × 13–18 mm (vs. ca. 6 × 3.5 mm).

A comprehensive morphological and taxonomic revision of Thismia abei (Thismiaceae), a mycoheterotrophic species endemic to Japan, is presented. The history of its discovery and subsequent studies is overviewed, and the actual place of valid publication of its basionym, Glaziocharis abei, is established. The typification of T. abei is revised accordingly, and a drawing that illustrated the first documented record of the species is designated as a new lectotype. The current knowledge of the morphology of the species is updated based on new data on its floral anatomy, as follows. The inner tepals are confirmed to be postgenitally fused into a mitre. The stamens are shown to be united into a tube through perfect postgenital fusion. Each anther theca consists of two microsporangia, and the anther is thus tetrasporangiate. Each microsporangium dehisces by its own longitudinal slit. The pyramidal structure terminating the stylar column is demonstrated to consist largely of free styles (which are united into a tubular portion only at the base of this structure). The styles are proven to bear paired stigmas at their bases. For the first time, detailed photographs of the flower structure of T. abei are published herein. The current knowledge of the geographical distribution of the species is summarised and shown on a map. Its conservation status is assessed as Critically Endangered (CR).

Societal Impact Statement Tiny, leafless fairy lanterns are easily overlooked on the forest floor. Thismia abei, endemic to Japan, persists in small, unstable populations and is listed nationally as Critically Endangered. Our recent work has revealed another, less obvious form of obscurity. The original source of the scientific name has long been cited incorrectly because a later, more widely read academic account displaced an earlier, valid description in a local periodical that some taxonomists dismissed as nonacademic. The case of T. abei is not unique; many similar works were likely treated in the same way. This example underscores the importance of careful nomenclatural study and better access to regional publications so that plant diversity is accurately documented and properly recognized. Summary Thismia abei is a minute, mycoheterotrophic plant that emerges above the leaf litter in summer. Here, we present a comprehensive review of T. abei by integrating recent findings on its morphology, phylogenetics, ecology, and nomenclatural history. Phylogenetic analyses place T. abei among the early-diverging lineages of the Old World Thismia clade, and current taxonomy assigns it to Thismia sect. Labiothismia. Its stamens are united into a tube along part of their length, although they were previously regarded as free. This misinterpretation has hindered comparisons between Old World and New World lineages. The species exhibits high mycorrhizal specificity and is associated primarily with two Rhizophagus virtual taxa (Glomeraceae). The fungus gnat Bradysia atracornea (Sciaridae) has been observed visiting its musty-scented flowers, consistent with the hypothesis that some fairy lanterns exploit fungus-associated cues. Beyond its biological elusiveness, T. abei also has an obscure nomenclatural history. In a Japanese academic climate in which influential botanists shaped prevailing views of what counted as effective publication, a later and more prominent account became the standard citation for the name, obscuring the earlier protologue that had been effectively published in a regional periodical. This case suggests that substantial taxonomic information remains hidden in regional Japanese publications. In addition, the publication history of T. abei, involving collaboration between a local naturalist, Chikaichi Abe, and a professional botanist, Yoshiyuki Akasawa, illustrates how such partnerships can bring overlooked plants to scientific attention and foreshadows key features of modern citizen science.

The Asian genus Epirixanthes (Polygalaceae) is one of the several mycoheterotrophic lineages of eudicots, being also the sole non-photosynthetic group in the order Fabales. Epirixanthes is subdivided into seven species, two of which were described as recently as in the 2010s. Despite the low species diversity and broad geographical distribution across tropical Asia of some of its species, the evolution and biology of Epirixanthes have been insufficiently understood, and this has, in turn, hindered its taxonomic understanding and specimen identification. In this study, we provide the first comprehensive phylogenetic reconstructions of Epirixanthes that cover all its seven currently accepted species. Three of these species have never been included before in any phylogenetic analysis. Using high-throughput sequencing, we obtained original data on the DNA structure of 16 specimens belonging to the seven species of Epirixanthes (including the type gatherings of E. compressa and E. confusa) as well as of three outgroup species (Polygala karensium, Salomonia ciliata, and S. cantoniensis). The sampling was supplemented by 17 previously studied specimens. We employed the ITS and matK markers used in the earlier reconstructions of Epirixanthes, and expanded the set of markers by utilizing the nuclear ETS region and 18S gene and 10 protein-coding plastid genes. We also explored the morphological evolution of Epirixanthes through ancestral state reconstructions of 13 characters of inflorescences, flowers, and fruits. We uncovered the species-level relationships within the genus, and demonstrated that E. confusa cannot be treated as a species distinct from E. elongata; this idea is supported by the morphological evidence, and therefore we formally synonymized E. confusa with E. elongata. We reconstructed a partial portrait (comprising seven characters) of the last common ancestor of Epirixanthes. Evolution of most characters was found to be homoplastic, which is partly explained by intraspecific variation, and partly also by the considerable morphological similarity between the distantly related E. compressa and E. elongata. Our results provide a basis for a taxonomic revision of Epirixanthes at a worldwide scale, as well as a framework for the DNA barcoding of its species.

This study contributes to the knowledge on the diversity of Psychotria in Vietnam, dealing with three of its species. Psychotria magnifructa is described as a new species based on the specimens recently collected in Kon Tum Province, central Vietnam. The new species is characterized by tomentose twigs and outer surface of stipules, horn-like projections on corolla lobes, and relatively larger fruits. Psychotria monticola is reported as a new record for Vietnam, expanding its known distribution eastward from India, Bangladesh, Myanmar, Peninsular Malaysia and Thailand. Information on P. balansae in the country is also provided. For the two latter species, the original material is analyzed, and lectotypes are designated. For each species, information on morphology, worldwide distribution, phenology, ecology, and a vernacular name is provided, as well as relevant notes and analytical photographic illustrations.

Aspidistra congestiflora discovered in a karstic limestone area in central Laos (Vientiane Province, Vang Vieng District) is described and illustrated as a species new to science. It is characterized by obconoid perianth tube, triangular perianth lobes without appendages, and widely obconoid pistil with prominent longitudinal ridges. The new species is morphologically most close to A. zhangii, from which it differs in longer petioles and purple-violet flowers. In addition, A. congestiflora is similar to A. leucographa, A. longhuiensis, A. opaca, and A. papillata in the general flower appearance, but readily differs from these four species in obconoid pistil. Aspidistra congestiflora is also similar to A. obtusata in the shape of flower (including obconoid pistil), as well as in its general appearance, but differs in often finely verruculose perianth lobes, larger pistil with longitudinal ridges, and purple-violet stigma. The newly discovered species is expected to be a local endemic and will probably need protection in the near future.

The paper continues a series of contributions aimed to develop a phylogenetically sound sectional subdivision of the mycoheterotrophic genus Thismia. Here, a formal taxonomic status is provided for a remarkable monophyletic Asian group of species that is also well-defined morphologically within the genus. It is demonstrated that no supraspecific taxon name of any rank is available for this group. Hence, a new section, Thismia sect. Mirabiles, is established. Inconsistencies are highlighted in the earlier treatments where the species placed here in Thismia sect. Mirabiles were assigned to Thismia sect. Sarcosiphon. Indeed, in all such treatments, either the taxon monophyly or the nomenclatural applicability of the latter sectional name is violated. A checklist of the newly described section is provided along with an identification key to its species. The section is currently known to comprise eight species mainly distributed in mainland Southeast Asia and including a species endemic to the Andaman and Nicobar Islands.

An overview of the genus Osmanthus (Oleaceae) in Vietnam is provided. Four species are recognized, of which O. heterophyllus and O. yunnanensis are newly recorded for the country. Results of a molecular phylogenetic study are reported, and employed for clarification of the species idendity of the Vietnamese collections assigned to O. fragrans. In addition, uncertainties in phylogenetic relationships between the sections of Osmanthus are highlighted. For each species, taxonomic and nomenclatural notes are given, along with geographical distribution and analytical illustrations; accounts of the two newly recorded species are supplemented by morphological descriptions and notes on their ecology and phenology. Lectotypes are designated for three names currently treated within the genus Osmanthus. A key for identification of the Vietnamese species of Osmanthus is presented.

Vaccinium pseudobullatum W. P. Fang & Z. H. Pan, Acta Phytotax. Sin. 19 (1): 108 (1981). Fig. 2 Type. China. Yunnan Province • Malipo County, Tiechang, 1200 m a. s. l., 20 February 1940, C. W. Wang 86988 [fl.] (holotype: PE; isotypes: IBK, IBK 00302352!; IBSC, 0457816!; KUN, 12088909! & 12088910!; SZ, 00126560!; WUK, 0268189, image!). Notes. Based on the specimens cited in Appendix 1, we have clarified two androecial features of the species: The length of the stamen filaments was indicated in the protologue (Fang and Pan 1981) as 1–1.5 mm, which was repeated in Fang and Stevens (2005). Fang (1991) and Huang and Fang (1991) considered the range as 1–2 mm. In most of the specimens studied here, however, the filaments are 3–4 mm long. Both flowering gatherings listed by Fang and Pan (1981; Wang 86988 and Feng 13490) bear flower buds (and no fully open flowers), and we suppose it to be the reason that they indicate shorter filaments than those observed by us. Their description was likely reproduced in the subsequent account without additional investigation of flower structure. The ratio of anther tubules to thecae was uniformly indicated as 2–3 for this species (Fang 1991; Huang and Fang 1991, including fig. 105 (9, 10); Fang and Stevens 2005), whereas we observed it to be mostly 1.1–1.3. We therefore treat this feature as more variable than earlier thought. Distribution. S China (SE Yunnan, SW Guangxi), N Vietnam (Cao Bang, Ha Giang). Until recently, the species was considered to be endemic to Yunnan; it was reported from Guangxi by Wei (2023) and from Vietnam by Averyanov et al. (2020).

Vaccinium bidoupense Smitinand ex Y. H. Tong, N. T. T. Huong & Tagane sp. nov. Figs 3, 4, 5, 6 Type. Vietnam. Kon Tum Province • NW slopes of Ngoc Linh Mountain system at 1800–1900 m a. s. l., open places in primary evergreen dense mountain forest, 23 February 1995, L. V. Averyanov, N. T. Ban, N. Q. Binh, A. Budantzev, L. Budantzev, N. T. Hiep, D. D. Huyen, P. K. Loc, N. X. Tam, G. Yakovlev VH 053 [fl.] (holotype: HN!; isotypes: BRIT, BRIT 402341!; LE, LE 01041972!; MO, 5168102!; P, P 04485557! & P 04483084!). Diagnosis. Vaccinium bidoupense is morphologically similar to V. petelotii and V. pseudobullatum in its relatively large leaf blades and umbel-like inflorescence with short rachis. It differs from V. petelotii in having longer calyx lobes (5–6 mm vs. 2.5–3 mm), pale red to salmon pink (vs. pale green) corolla, a longer corolla tube (11–13.5 mm vs. 3.5–4.5 mm), and longer stamens (14–16 mm vs. 5–6.5 mm). The new species differs from V. pseudobullatum in having leaf blades with somewhat less obvious tertiary veins, and longer pedicels (7–14 mm vs. 4–7 mm), corolla tube (11–13.5 mm vs. 8–9 mm) and stamen filaments (8–9 mm vs. 1–4 mm) (Table 1). Description. Shrubs, epiphytic or epilithic, evergreen; shoots pendent, ca. 2–5 (– 10) m long, sometimes rooting at nodes. Branches more or less angled, glabrous, densely lenticellate. Leaves non-distichously alternate (but leaves of a branch often arranged in one plane due to twisted petioles), evenly scattered. Petiole 0.3–1.2 cm long, glabrous. Leaf blade ovate to lanceolate or sometimes elliptic, 12–22 × 4.7–11.7 cm, 2.0–3.7 times as long as wide, coriaceous; adaxial surface green, glabrous; abaxial surface pale green, densely covered with appressed dark brown trichomes (trichomes caducous, leaving faintly punctate scars); base rounded, subtruncate or shallowly cordate, rarely cuneate or prominently cordate; margin entire, slightly revolute, with 1 basal gland per side, glands 1–1.5 mm in diam.; apex acute to acuminate or shortly caudate; median vein and secondary veins impressed adaxially, strongly raised abaxially; secondary veins pinnately arranged, 10–14 on each side of median vein, usually meeting in a closed loop and forming an intramarginal vein; tertiary veins more prominent in submarginal area than in the rest of leaf blade, stout, reticulate, slightly impressed or sometimes flat adaxially, slightly raised abaxially. Inflorescences axillary, 1 per axil, on leafy shoots and older leafless branches, sessile (peduncle absent), racemose, umbel-like, determinate (developing mostly within the confines of the perennating buds), 4–10 - flowered; rachis pale green, 0.5–2 cm long, glabrous; bracts caducous, crimson, ovate, 1.0–1.5 × 0.5–0.6 cm, thinly coriaceous, glabrous, margin entire, apex obtuse. Flowers pendent, articulated with pedicels, 5 - merous. Pedicels red to pale green, 0.7–1.4 cm long, glabrous; bracteoles 2, attached at base of pedicel, subopposite, acicular, early caducous. Calyx (excluding ovary) pale red to salmon pink, becoming greenish with age, at base appressed to corolla and distally diverging to spreading, glabrous on both sides; tube ca. 1 mm long; lobes 5, triangular-lanceolate, 5–6 × 2–3 mm, distinctly 1 - veined. Corolla pale red to salmon pink, glabrous outside and inside; tube cupulate, 11–13.5 × 13–14 mm; lobes 5, strongly recurved, triangular to broadly triangular, 3–4 × 4–5 mm. Stamens 10, dimorphic with respect to spurs, included in corolla, free from each other, 14–16 mm long; filaments white to pale pink, slightly incurved, 8–9 mm long, glabrous in proximal half and puberulent in distal half; anthers tightly appressed to style, golden yellow, dorsifixed, 7–9 mm long, each with 2 spurs; thecae 3–3.5 mm long, slightly papillate; tubules parallel, 4–6 mm long (ca. 1.3 times as long as thecae), opening by oblique ventral apical pores; spurs borne dorsally at base of tubules, strongly curved, ca. 1 mm long, those on antesepalous stamens extending laterally outside of antepetalous anthers and overlapping with spurs of next antesepalous stamens, those on antepetalous stamens strongly hooked outward below spurs of antesepalous stamens. Ovary inferior, pale red to salmon pink, obconic, terete, 1–2 × 2–2.5 mm, glabrous, pseudo- 10 - locular; disk pale yellow, annular, broadly dome-shaped, ca. 2.5 mm diam., glabrous; style 1.4–1.6 cm long, exserted from corolla for 2.5–4 mm, linear, glabrous; stigma truncate. Infructescences with rachis 1–3 cm long. Fruiting pedicel 1.2–2.4 cm long. Fruit (when young) globose, ca. 6 mm in diam., glabrous, with persistent calyx lobes 5–6 mm long. Mature fruits and seeds unknown. Ecology and phenology. Vaccinium bidoupense grows as an epiphyte on tree trunks or as a lithophyte on mossy rocks in broad-leaved and mixed forests at elevations of 1100–2200 m. It flowers from October to February; young fruits are documented from May to June. Distribution. Vaccinium bidoupense is known from Laos (Sekong Province) and Vietnam (provinces Kon Tum, Lam Dong, and Quang Nam). The species is therefore endemic to the area comprising the Central Highlands of Vietnam (also called Tay Nguyen Plateau) and their extension in Laos known as Dak Cheung (or Dakchung) Plateau, being broadly distributed across this region. The region comprises three main mountainous areas, i. e., Dak Lak Plateau, Kon Tum — Gia Lai Plateau and Langbian Plateau (Poyarkov et al. 2021), and V. bidoupense is documented to inhabit the latter two areas. As the known locations suggest, the species probably occurs throughout the Central Highlands, and its presence in the provinces Dak Lak, Dak Nong and Gia Lai is especially probable. Etymology and history of documentation of Vaccinium bidoupense. The species name “ Vaccinium bidoupense ” was initially proposed by Tem Smitinand on the determination slips of three of Poilane’s specimens kept in P (30292, 30763 and 30909, included below as paratypes of the species). Two of these specimens originated from the Bidoup Massif (and 30292 was collected nearby), which is reflected in the species epithet. Although such a name has never been formally published until now, it was used by Vander Kloet and Avery (2007) (as “ V. bidoupense Smithin ”) who included the specimen Poilane 30763 in a morphophenetic analysis of stamen characters in the tribe Vaccinieae. Here, we follow Smitinand’s choice of epithet to ensure the clearness of the species identity and to acknowledge his recognition of this distinct species. Conservation status. Vaccinium bidoupense is an integral element of highland vegetation of the Central Highlands of Vietnam (including their extension in Laos) with an expected total extent of occurrence (EOO) of about 55,000 km 2, which does not fit any of the threatened IUCN Red List conservation categories (IUCN, Standards and Petitions Committee 2025). In intact habitats of montane forests, the species meets no damage factors. However, the vast degradation of primary vegetation across the distribution area of the species, including the legally protected territories, leads to a continuing decline in the extent of its occurrence, quality of habitat, number of populations, and number of mature individuals. In this connection, we preliminarily assess V. bidoupense as Near Threatened (NT); we also consider that the species is close to being qualified as Vulnerable (VU) in the near future. Additional specimens examined (paratypes). Laos. Sekong Province • [Dak Cheung District,] new road along the border with Vietnam, 15°34′36.0′′N, 107°20′11.5′′E, 1224 m a. s. l., 17 July 2021, P. Souladeth, M. Soukhavong, N. Thongphakdee, T. Boutavong 1141 [st.] (FOF, FOF 0009576; KAG, KAG 181621). Vietnam. Quang Nam Province • Nam Giang District, Song Thanh Nature Reserve, 15°33′07′′N, 107°23′02′′E, 1100 m a. s. l., 6 May 2019, M. S. Nuraliev 2509 [young fr.] (BRIT, BRIT 1150627; IBSC; MW, MW 0758862, MW 0758863 & MW 0758864). Lam Dong Province • N of Dalat, 1500 m a. s. l., 2 September 1940, E. Poilane 30292 [young fr.] (L, L.3786302, image; P, P 04484682, P 04484683, P 04484684, P 04484685, P 05244320 & P 05244322, images) • Bidoup Massif, 2200 m a. s. l., 12 October 1940, E. Poilane 30763 [fl.] (L, L.3786303, image; P, P 00647856, P 04484686, P 04484688, P 05244702 & P 05244703, images) • ibid., 2000 m a. s. l., 14 October 1940, E. Poilane 30909 [fl.] (P, P 04484687, P 05244317 & P 05244321) • Lac Duong District, Da Chay Municipality, 29 km to NE from Dalat City, 12°6′N, 108°39′E, 1900–2000 m a. s. l., 23 March 1997, L. V. Averyanov, N. Q. Binh, P. K. Loc VH 3118 [st.] (HN; LE, LE 01041973; MO, MO-5172316) • ibid., 12°6′N, 108°39′E, 2150 m a. s. l., 1 May 1997, L. V. Averyanov, N. Q. Binh, N. T. Hiep, P. K. Loc, P. Lowry VH 4463 [fr.] (HN; LE, LE 01041976; MO, MO 2080998; MW, MW 1045967; P, P 04483084) • Lac Duong District, Bidoup Nui Ba National Park, 12 October 2011, N. H. Xia, J. B. Ni, Y. H. Tong & X. R. Zheng TYH- 1070 [st.] (IBSC) • ibid., SE of Giang Ly station, 12°11′07.7′′N, 108°41′14.6′′E, 1509 m a. s. l., 23 December 2012, A. N. Kuznetsov, S. P. Kuznetsova, A. N. Demidova, N. G. Prilepsky 404 [st.] (MW, MW 0750311) • ibid., 12°10′21.03′′N, 108°41′49.76′′E, 1504 m a. s. l., 19 November 2014, H. Toyama, S. Tagane, V. S. Dang, H. Nagamasu, A. Naiki, H. Tran, C. J. Yang et al. V 1857 [fl.] (FU; VNM) • ibid., 12°11′11.18′′N, 108°42′53.12′′E, 1639 m a. s. l., 23 February 2016, S. Tagane et al. V 4287 [fl.] (DLU; FU; VNM) • ibid., 12°11′09.23′′N, 108°42′55.46′′E, 1637 m a. s. l., 22 December 2018, S. Tagane et al. V 9614 [fl.] (DLU; FU; KAG, KAG 127364) • ibid., 22 April 2019, T. Yahara et al. V 9879 [young fr.] (DLU; FU; KAG, KAG 182510) • ibid., 12°4.076′N, 108°38.927′E, 2000–2200 m a. s. l., 8 November 2023, L. V. Averyanov, V. C. Nguyen, B. V. Truong, T. Maisak AL 2537 [fl.] (LE, LE 01253935, photos LE 01124590).

A historical and taxonomic overview of the genus Decaisnea (Lardizabalaceae) is provided, and the nomenclature of this generic name is reviewed and corrected. For each of its two currently accepted species, D. fargesii and D. insignis, the original material is revised, typification is clarified, and collection details of the type specimens are revealed. For both species, knowledge on their morphology, ecology and geographical distribution is updated. Evidence of the presence of Decaisnea in the flora of Vietnam is summarized; its presence in the country is confirmed for the first time by specimen revision. In Vietnam, the genus is shown to be represented by D. fargesii, which is known solely in Lao Cai Province, Hoang Lien National Park. The diversity of Lardizabalaceae in Vietnam is reviewed, and a key to the Vietnamese genera and species of the family is presented.

Memecylon longipedunculatum, a new species of Melastomataceae, is described and illustrated. The species is known to occur in Khanh Hoa and Ninh Thuan provinces in South Central Coast Vietnam, where it is restricted to low dry coastal forests and scrubby vegetation. The description is based on the authors’ original gatherings as well as on the historical collections made a century ago. The new species is distinguishable from most of its congeners by small leaves (1.2–5.7 × 0.7–2.4 cm) with obtuse or sometimes emarginate apices, long peduncles (1–2.7 cm long), and crescent-shaped anther connective with distinct centrally placed gland.

The paper presents new data on the diversity of Aspidistra in Vietnam obtained during the fieldwork of 2025 in the Central Highlands (also known as Tay Nguyen Plateau). It includes four taxa new to science, viz. the species A. microstyla and A. nguyenii and the varieties A. brachypetala var. danii andA. mirostigma var. haui. Aspidistra brachypetala is reported here as a new species record for Vietnam. For each taxon, information on morphology, ecology, phenology, conservation status and distribution is presented, as well as relevant taxonomic notes and analytical photographic illustrations.