Spiradiclis cavicola L. Wu, Hareesh & B. Pan (Rubiaceae), a new species from limestone caves in Guizhou and Guangxi provinces, southwestern China, is described and illustrated. It is morphologically similar to S. scabrida, but can be easily distinguished by its 0.5–3 cm long petiole, elliptic to oblong leaf blade, and homostylous flowers with anthers and stigma positioned at the throat of corolla tube, or sometimes stigma slightly above anthers.

Several nomenclatural changes in Polygonatum (Asparagaceae) are made based on field, herbarium, and molecular studies. Polygonatum govanianum is recognized at specific rank, P. dolichocarpum is considered a synonym of the earlier P. gongshanense, and P. sinopubescens is treated as a synonym of P. filipes. Maps of distribution are included for P. campanulatum and P. gongshanense which are newly reported for Myanmar, and for P. tessellatum which is newly reported for India.

Shorea peltata (Dipterocarpaceae), categorized according to IUCN classification as Critically Endangered, is reported for the first time from Sarawak, NW Malaysian Borneo. New data on its distribution, locations' geological characteristics, and the first published description of shoot innovations are presented. Plants from ultrabasics in NE Sabah were excluded from S. peltata as an undescribed taxon for which better material is required to enable formal description. Although conservation status of Peninsular Malaysian populations of S. peltata is Critically Endangered, on Borneo S. peltata is considered Endangered, and its Sumateran populations require conservation reassessment.

The identity of Arisaema pangii H. Li (Araceae) has been doubtful ever since it was published. Various authors treated it under either A. nepenthoides or under A. wattii. Arisaema pangii is recognized as a distinct species based on morphological and molecular data, and it is placed in sect. Nepenthoidea. A detailed description, notes on the taxonomy and colour images are provided for easy identification.

Argostemma vietnamicum B.H. Quang, Joongku Lee & R.K. Choudhary, a new species of Rubiaceae from Thua-Thien Hue Province of central Vietnam is described and illustrated. It is morphologically similar to A. discolor and A. bariense, but differs from them by having considerably shorter petioles, round to obovate leaf laminae with a round base, obsolete secondary veins, 1–4-flowered inflorescences, much shorter peduncles and pedicels, different bracts, a glabrescent to glabrous calyx, and a shorter corolla tube. An identification key to the species of Argostemma known from Vietnam is provided.

A new name Diospyros minutisepala Kottaim. (Ebenaceae) is proposed as a replacement name for the extant species Diospyros microcalyx D.X. Nong, Y.D. Peng & L.Y. Yu because this name is already occupied by a fossil species.

Impatiens deflexipetalum Biseshwori, Bipin & D. Sahoo (Balsaminaceae) is described as a new species from Senapati District of Manipur, NE India. It is distinguishable from I. adamowskiana by its four-angular, reddish and dentate stem, elliptic leaves, pinkish white flowers, red lateral sepals, and a pinkish lower sepal and dorsal petal.

As part of taxonomic revision of Flemingia (Fabaceae), we describe and illustrate F. langbiangensis T.V. Do, B. Xu & X.F. Gao as a new species from southern Vietnam. Flemingia langbiangensis is morphologically similar to F. latifolia, F. ferruginea and F. macrophylla, but it differs from those by glabrescent branchlets; a subcapitate-like raceme with flowers condensed to the apex; a broadly ovate bract about half of the calyx length, 5–6 × 4–5 mm, densely brownish villous outside, with black glands inside; subsessile flowers with a greenish to pink corolla that is as long as or slightly longer than calyx; and pods that are of the same length as calyx. Additionally, F. prostrata Roxb. is lectotypified and together with F. sootepensis reported as new for Vietnam. A diagnostic key to the twelve Vietnamese species of Flemingia is provided.

A new species, Hoya pulchra Aurigue & Cabactulan (Apocynaceae), is described and illustrated. It is compared with the similar H. waymaniae, endemic to Borneo, from which it differs in lamina shape (lanceolate with a flat edge vs. elliptic-ovate with undulate edge) and the absence of bilobed apex in the outer corona lobe apex vs. a short raised bilobed apex.

The replacement name Psychotria enneantha I.M. Turner is proposed for P. magnisepala Sohmer, an illegitimate later homonym.

Using flow cytometry we explored the cytogeography of Seseli libanotis (Apiaceae) from central Europe and several adjacent areas. We detected diploids and tetraploids, but no triploids. Diploids are distributed across nearly all study areas, whereas tetraploids occur in Czechia, the Pannonian lowlands of northeastern Austria and western Slovakia, in southeastern Slovakia, in the Eastern Carpathians and the Apuşeni Mts in Romania, and in Croatia. The distribution of cytotypes is nearly allopatric. Only in some regions on the northern border of the Pannonian basin, in southern Poland and in Romania they are parapatric. Only one mixed-ploidy population (located in Poland) was detected. In Czechia and Slovakia, we did not find differences in the elevational distributions of cytotypes; tetraploids, however, seemed to have a broader elevational range and slightly prevail at lower elevations. Using sequencing of the trnL-trnF region of cpDNA we detected high haplotype diversity with no relation to cytogeography (longitude, latitude or elevation).

Staurogyne caobangensis D.V. Hai & Joongku Lee (Acanthaceae), a new species from Vietnam is described and illustrated. It has a densely-flowered inflorescence and several unique features of bracts, bracteoles, calyx and fruits. It is morphologically similar to S. chapaensis, S. petelotii and S. sesamoides. Illustrations, description, ecology, and habitat information of the new species as well as an identification key to the Vietnamese species of Staurogyne are provided.

A new moss species, Didymodon daqingii J. Kou, R.H. Zander & C. Feng (Pottiaceae) from the Daqing Mountains in semi-arid region in Inner Mongolia, China is described and illustrated. It is characterized by long-lanceolate leaves that are appressedincurved when dry; subulate, very fragile and bistratose leaf apices; abruptly broadened and rounded leaf bases; distally bistratose leaf margins that are recurved in proximal 1/2–3/4; long-excurrent costa with guide cells in 2–3 layers; papillose distal laminal cells, and yellow-green KOH laminal color reaction. Following recent Zander's revisionary work of the genus Didymodon s. lato, D. daqingii belongs in the emended genus Didymodon s. stricto. It is compared with morphologically similar species and its habitat ecology is discussed.

Stipa khovdensis L.Q. Zhao sp. nova (Poaceae), is described and illustrated from Mongolia. It is morphologically similar to S. argillosa of Stipa section Barbatae, but differs from it by its longer glumes (28–35 mm vs. 13–16 mm in S. argillosa) with the apex scarious and acuminate into a fragile filiform extension, longer anthecium (11–12 mm vs. 7–8 mm), and longer awn (14–16.5 cm vs. 8.0–9.5 cm). A checklist of and a key to the genus Stipa s. stricto in Mongolia are provided.

Hornstedtia annadeguzmaniae Naive & Alejandro (Zingiberaceae, Alpinioideae, Alpinieae), a new species from Mindanao, southern Philippines, is here described and illustrated. It is morphologically closely similar to H. lophophora but differs from it by having an ovate, lanate, brownish green ligule, dorsoventrally puberulous labellum, and pale magenta corolla lobes. We provide information on the distribution and habitat ecology as well as a key to the six Hornstedtia species known from the Philippines.

We describe and illustrate Aristolochia nuichuaensis (Aristolochiaceae) as a new species from southern Vietnam. It has a cordate leaf blade, an up to 16(20)-cm-long inflorescence axis, a strongly constricted, oblong cylindrically-shaped upper part of tube, with outer surface uniformly purple, inner surface uniformly white, a campanulate limb, 4.5–5.0 cm in diam., with non-revolute lobes, a whitish outer surface of limb with visible purple streaks, a white inner surface of limb with sunken dark-purple streaks and verrucoses, an elliptic and white throat, and a gynostemium with three acute lobes. Its phenology, ecology, and comparisons with some morphologically similar species are presented. The diagnostic characters place A. nuichuaensis in the subgenus Siphisia. We also provide an identification key and a checklist with information on the distributions of the known Siphisia species in Vietnam.

Centaurea khosraviana Negaresh sp. nova (Asteraceae) from West Azerbaijan Province, NW Iran, is described and illustrated. It is morphologically most similar to C. carduiformis subsp. orientalis, but differs from it by having a perennial habit, a loosely hirsute-articulate indumentum on the stem and leaves, fewer lateral segments of basal and lower cauline leaves, smaller involucres, a densely arachnoid indumentum on the phyllaries, narrower appendages, fewer cilia, and a shorter spine. In addition, the geographic distribution of the new species and closely related species is presented.

Ranunculus kobendzae Halamski sp. nova (Ranunculaceae) is a representative of the partly apomictic R. auricomus complex and is characterised by undivided, reniform radical leaves with a very wide basal angle, segments of stem leaves with partly slender teeth, mostly imperfect flowers, and pilose, ovate to cylindrical tori (receptacles) with a marked intervallum. Similar microspecies of the R. auricomus complex are R. uplandicus, R. allemannii, R. ganeschinii, R. neumannii, R. zmudae and R. mendosus, but the combination of characters of radical and stem leaves of R. kobendzae is unique. At the type locality in Lipka (Dębina) near Warszawa (Warsaw, capital of Poland), R. kobendzae grows in an oak–hornbeam forest, and in three other locations in central Poland (Puszcza Słupecka, Brańszczyk and Błogie) in hornbeam or alder forests. The DNA ploidy level was determined by propidium iodide flow cytometry from a dried herbarium specimen and was found to be tetraploid (2n = 4x).

A species of Euphorbia sect. Esula (Euphorbiaceae) from the Western Tian-Shan, Central Asia, is described as new to science. Euphorbia talassica sp. nova occurs in the Talas Mountain Range in Kazakhstan and Kyrgyzstan, and falls into E. ser. Andrachnoides because of its relatively short and broad leaves. Euphorbia talassica is most similar to E. irgisensis, from which it differs by having a slender and spreading rootstock (vs. a vertical taproot), and incrassate (vs. thin) leaves. The new species also grows at much higher elevations. Euphorbia ser. Andrachnoides is overviewed for Central Asia and adjacent areas, with seven species discussed and mapped.

Historical (mainly 1930s) and contemporary records of 482 vascular plant species or genera of non-littoral areas of 464 islands in the archipelago of SW Finland are compared, to visualise changes in distribution patterns, and to identify environmental variables that affect the distribution of the species. The environmental variables were measured in a GIS. Logistic regression analysis was used to find variables that affect the probability of species occurrences. Results, with distribution maps, are presented for each species. The families Trilliaceae, Asparagaceae, Amaryllidaceae, Iridaceae, Orchidaceae, Araceae, Alismataceae, Scheuchzeriaceae, Juncaginaceae, Juncaceae and Cyperaceae are presented in this sixth part of the series. A synthesis of the study will be presented in the last part of this article series.

Pterichis aragogiana Kolan. & Szlach. sp. nova (Orchidaceae) is described and illustrated based on Ecuadorian material. It can be distinguished from other species of sect. Pterichis by the narrow, almost linear petals, sepals with almost caudate apical portions, prominent lip middle lobe which is longer than the basal part of the lip, and by the apical part of the lip middle lobe which is non-fleshy and lacks any distinctive glands. So far two populations of P. aragogiana are known, both from páramo in the Andean region.

Here we present revised taxonomy, morphological variation and geographical distribution of Jasminum pedunculatum Gagnep. (Oleaceae). Type material of this species was analyzed and a specimen from P (P00644297) was designated as a lectotype. Jasminum albicalyx Kobuski is reduced to a taxonomic synonym of J. pedunculatum on the basis of morphological features and geographical occurrence. A full list of all available specimens of J. pedunculatum s. lato and a map of its distribution are provided. The species is widely distributed throughout Guangxi (China) and in northern Vietnam. A drawing and colour photographs of J. pedunculatum are provided to aid identification.

A new species, Lasianthus bidoupensis V.S. Dang & Naiki (Rubiaceae) is described and illustrated from Bidoup Nui Ba National Park, Lam Dong Province, southern Vietnam. It resembles L. yaharae which was recently discovered from Mt. Hon Ba and L. dalatensis which is endemic to Dalat, southern Vietnam. However, L. bidoupensis differs from them by having larger leaves and bracts, longer petioles, stipules, calyx and corolla tubes, and deep-red mature fruits.

Canthium longipetalum Y.H. Tan & S.S. Zhou, a new species of Rubiaceae from Putao, Kachin State, Myanmar, is described and illustrated. It is morphologically similar to C. neilgherrense which has ca. 3 mm long pedicels and corolla lobes, but differs from it by having 2.5–3.2 cm long pedicels and 1.2–1.4 cm long corolla lobes.