Quoc Bao Nguyen

Peliosanthes rigidifolia, a new species discovered in central Vietnam, is described and illustrated. It is readily distinguished from all its congeners by its stamens that are entirely free from each other, non-epitepalous, and possess small anthers scarcely exceeding the filaments. A detailed morphological description of the new species is presented along with information on its ecology, phenology, conservation status, and distribution, as well as relevant taxonomic notes and analytical photographic illustrations.

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.

Chiloschista acuticallosa (Orchidaceae, Vandeae, Aeridinae) is described here as a new species to science from Cao Bang Province, Northern Vietnam. The floral shape and color pattern of the new species may lead to misidentification as C. eckhardii, C. glabrisepala, or C. quangdangii. Among these species, our plant morphologically is closest to C. eckhardii but differs in having ovate-oblong lateral lip lobes, a conoid, pointed callus on the lip disc, a trapezoid backwall callus with four irregular teeth, an oblong column foot, and semi-elliptic stelidia. Data on the ecology, phenology, distribution, and relevant taxonomic notes for the new species are presented. The conservation status of the new species is preliminarily assessed as Data Deficient (DD) following the categories and criteria proposed by the IUCN Red List.

A new species of Camellia (section Piquetia) from south-central of Vietnam is described. Within section Piquetia, the new species is most similar to C. honbaensis, but differs in several morphological traits (smaller leaves, longer reddish pedicels, glabrous stamens, and styles completely free from the base). This study provides a standard taxonomic description, together with morphological comparisons between the new species, Camellia honbaensis, with other similar species and additional information on the species habitat, estimated conservation status, and the anatomy of its leaves and branches.

Begonia hanhhoae, a new species from Khanh Hoa Province, Ninh Hoa District, South Central Coast region, Vietnam, is described and illustrated. It resembles B. aspersa from northern Vietnam but differs in having broadly ovate to suborbicular leaves (vs. reniform) with a slightly waxy adaxial surface (vs. velvety), inflorescence with up to 13 flowers (vs. up to 5), actinomorphic androecium (vs. zygomorphic), and pistillate flowers that are subsessile or borne on very short pedicels up to 1.5 mm long (vs. 4–12 mm). According to the IUCN criteria, it has been tentatively assessed as Endangered (EN).

Curcuma clovisii Škorničk., formerly known as Stahlianthus thorelii Gagnep., has a restricted distribution in Thailand, Laos, Cambodia, and Vietnam. The present study provided detailed observations the micro-morphological characteristics of the rhizome, leaf, root, pseudostem, and petiole of this species. The rhizome and leaf anatomy were consistent with previous descriptions of S. thorelii, while the micro-morphological characteristics of the root, pseudostem, and petiole are reported here for the first time. In addition, the ITS and trnL regions of C. clovisii were successfully amplified and sequenced. Phylogenetic analyses based on these two molecular markers confirmed the placement of C. clovisii within the Zingiberaceae, with C. clovisii and other Stahlianthus species forming a single clade fully embedded within the genus Curcuma. Together, these findings strengthen the evidence supporting the transfer of all Stahlianthus species into Curcuma.

The paper provides a taxonomic assessment of Bulbophyllum section Racemosae in Vietnam, accompanied by an identification key for all species currently recognized in the country. Information on type specimens, distribution, habitat and phenology (when available), as well as relevant taxonomic notes are presented for each accepted species, accompanied by plates with analytical photos. Bulbophyllum minhquanii is described as new to science, and B. albidostylidium (identified earlier as B. putii) is reported as a new national record. In total, 14 species of B. sect. Racemosae, of which five are endemic, are documented for Vietnam based on previous and current studies. The occurrences of B. macrocoleum and B. morphologorum in Vietnam remain uncertain and require verification by additional collections.

A new species of the genus Saprosma (Rubiaceae), S. nuichuaensis Q.T.Pham, V.S.Dang & Tagane, from Nui Chua National Park of Ninh Thuan Province, southern Vietnam, is described and illustrated. Saprosma nuichuaensis is closely related to S. ternata, but differs in having terete branches, smaller leaf blades, fewer secondary veins, shorter petioles, smaller calyx lobes, and seeds verrucose on the abaxial side. Photographs, vernacular name and preliminary conservation status are provided.