Geostachys angustifolia sp. nov. (Zingiberaceae) from Thailand

A new species of Geostachys (Bak.) Ridl. is described, G. angustifolia K. Larsen sp. nov., and a key to all species of the genus found in Thailand, Cambodia and Vietnam is presented.     

Pogostemon nudus sp. nov. (Lamiaceae) from Thailand

A new species of Pogostemon Desf., P. nudus Bongcheewin & Pramali, is described, illustrated and compared with the similar P. menthoides from Thailand. Morphological characters, especially the micromorphology of nutlets and leaf epidermis, and conservation status in accordance with the IUCN red list categories and criteria are described and discussed. In addition, a key to all species of P. sect. Pogostemon known from Thailand is presented.     

Typhonium muaklekense sp. nov. (Araceae) from Thailand

Typhonium muaklekense D. Sookchaloem & S. Maneeanakekul is described and illustrated. This new species resembles T. roxburghii Schott and T. varians Hett. & Sookch. in the spathe. Drawings, photographs and a table comparing diagnostic features of T. muaklekense, T. roxburghii and T. varians are provided.     

Oberonia pygmaea sp. nov. (Orchidaceae) from Thailand

In the context of an ongoing revision of the orchid genus Oberonia in Thailand, we describe and illustrate a new species under the name O. pygmaea Bunpha, H. A. Pedersen & Sridith. Vegetatively, the tiny new species is particularly similar to O. rufilabris Lindl. (widespread in mainland southeast Asia, including Thailand), whereas its floral morphology comes closest to the much larger O. costeriana J. J. Sm. from Sumatra, Java and Sulawesi. So far, O. pygmaea is only known from Pang Ung in the northern Thai province of Mae Hong Son, but we suggest that it should also be searched for in hill evergreen forest in adjoining parts of the Dawna Range, both in Thailand and Myanmar.     

Pseuderanthemum pubescens sp. nov. (Acanthaceae) from Thailand

Pseuderanthemum pubescens T. Choopan & P. J. Grote, a new species from southeastern Thailand is described and illustrated. It is distinguished from P. longistylum J. B. Imlay by leaves being pubescent instead of glabrous and by the corolla lobes being purple with reddish purple dots on all 5 lobes instead of dotted on lower lip only.     

Liparis rubescens sp. nov. (Orchidaceae) from Thailand

In the context of an ongoing revision of the orchid genus Liparis in Thailand, we describe and illustrate a new species under the name L. rubescens Tetsana, H. A. Pedersen & Sridith. Morphologically, it is particularly similar to L. dumaguetensis Ames from the Philippines, but it differs in the shape of the lateral sepals and in several characters of the labellum. Among the Liparis species already known from Thailand, L. atrosanguinea Ridl. bears a certain resemblance to the new species, but not so much as to make misidentifications likely. So far, L. rubescens is only known from Khao Nan National Park in the southern Thai province of Nakhon Si Thammarat, but we suggest that it should also be searched for in other parts of peninsular Thailand, southernmost Myanmar and Peninsular Malaysia.     

Phyllanthus brunelii sp.nov. (Euphorbiaceae) from Thailand

Phyllanthus brunelii Roux, a new shrubby species from Thailand is described. P. brunelii has apparently until now been confused with P. reticulatus Poir. Its pollen structure suggests affinities between the subgenera Kirganelia (A. Juss.) Webster and Gomphidium (Baill.) Webster.     

Piper viridescens sp. nov. (Piperaceae) from Thailand

Piper viridescens sp. nov. is proposed based on material from northern Thailand. The new species is described and illustrated, resulting from a revision of the genus in Thailand. The new species is most closely related to P. boehmeriifolium (Miq.) C. DC. A table comparing diagnostic features of P. viridescens, P. boehmeriifolium and P. retrofractum is provided.     

Aristolochia helix sp.nov. (Aristolochiaceae) from Thailand

A new species of Aristolochiaceae, Aristolochia helix , is described from Thailand and contrasted to its nearest ally, A. arenicola.     

Maclurochloa tonkinensis sp. nov. (Poaceae: Bambusoideae) from Vietnam

Maclurochloa K. M. Wong (Gramineae: Bambusoideae) is a genus of clambering bamboos with dry caryopses. It was thought to be monotypic in Peninsular Malaysia, but here we report one more species from Vietnam which is new to science: Maclurochloa tonkinensis H. N. Nguyen et V. T. Tran sp. nov. Maclurochloa tonkinensis is most similar to M. montana (Ridl.) K. M. Wong from which differs mainly by having internodes 50–58 × 3.0–3.5 cm and culm leaves with auriculate sheaths and erect blade.     

Rungia sinothailandica sp. nov. (Acanthaceae) from China and Thailand

Rungia sinothailandica (Acanthaceae), a new species from Yunnan, China and Chiang Rai, Thailand is described and illustrated. A colour plate, line drawing and distribution map of R. sinothailandica are provided. Rungia sinothailandica is similar to R. pinpienensis H. S. Lo, but differs in the broadly ovate sterile bracts and obovate‐elliptic fertile bracts, the crispate and tawny bracts margin, the 2‐lobed upper lip of the corolla and puberulent capsule. It is also similar to R. burmanica (C. B. Clarke) B. Hansen, but is easily distinguished by pubescent stems and leaves, the cymbiform‐oblong bracteoles and the 2‐lobed upper lip of corolla.     

Bauhinia sirindhorniae sp. nov. (LeguminosaCaesalpinioideae) a remarkable new species from Thailand

Bauhinia sirindhorniae sp. nov., from Nong Khai Province, Thailand is described and illustrated. The pollen morphology has been studied.     

Kaempfería grandifolia sp. nov. (Zingiberaceae) a new species from Thailand

Kaempfería grandifolia is described and illustrated from the Phu Phan National Park in NE Thailand. The somatic chromosome number is established to 2n = 22. Its affinities are discussed.     

Heterostemma trilobatum sp. nov. (Apocynaceae: Asclepiadoideae) from Thailand

A new species, Heterostemma trilobatum A. Kidyoo & Thaithong has been discovered in northern, northeastern and southeastern Thailand. It is here described, illustrated and meticulously compared with a morphologically similar species, H. xuansonense T. B. Tran & J. Hw. Kim. Both species resemble each other, having sessile to subsessile cymes, five glands on the inside of the calyx and dark red to purplish red ovate corona lobes. However, H.trilobatum is markedly differentiated by much smaller size of flowers and the presence of peculiar trilobed corona appendages.     

Centotheca ganeshaiahiana sp. nov. (Poaceae) from Andaman and Nicobar Islands,India

Centotheca ganeshaiahiana M. V. Ramana, Alok Chorghe, Prasanna & Sanjappa, a new species from Saddle Peak National Park, north Andaman, Andaman and Nicobar Islands, India is described and illustrated. It is closely allied to C. uniflora Swallen, a Vietnamese species, but differs mainly in shorter culms, leaf blades and inflorescences, longer pedicels, spikelets with 2 fertile florets and lemmas with bulbous based hairs.     

Samuelsia mundiveteris sp. nov. from Thailand

Samuelsia mundiveteris is described as the first member of the genus from the Old World tropics.     

Dischidia kerrii sp. nov. (Apocynaceae: Asclepiadoideae) from northeastern Thailand

Dischidia kerrii is presented as a new species from northeastern Thailand. This newly discovered species is thoroughly described, discussed and illustrated. A comparison is made with the putative closely related species D. acuminata. They can be distinguished by differences in corolla lobes and staminal corona lobes.