Hoya hanhiae sp. nov. (Apocynaceae,Asclepiadoideae) from central Vietnam

A new species, Hoya hanhiae V. T. Pham et Aver. discovered in central Vietnam is described, illustrated and compared with the related species H. macrophylla Bl. and H. verticillata (Vahl) G. Don.     

Hoya tengchongensis sp. nov. (Apocynaceae,Asclepiadoideae) from Yunnan,China

Hoya tengchongensis, a new species of Apocynaceae, subfamily Asclepiadoideae from Yunnan, China, is described and illustrated. The new species is morphologically similar to Hoya serpens in its creeping habit, bearing small and suborbicular leaves, and adaxially tomentose corolla. However, H. tengchongensis differs from H. serpens in corolla size (ca 7 mm versus ca 12 mm in diam) and corona morphology (corona lobes slightly ascending versus erect).     

Hoya longipedunculata sp. nov. (Apocynaceae,Asclepiadoideae) from Quang Nam,central Vietnam

A new species, Hoya longipedunculata (Apocynaceae, Asclepiadoideae), discovered in Quang Nam Province in central Vietnam is described and illustrated. It is morphologically similar to H. fusca, but differs by having a weak and shorter stem, thin leaf blade, umbel‐like inflorescence, longer hairy peduncle and long pedicel, as well as broad, narrowly‐ovate to triangular sepals, and wider, white opalescent (sometime abaxially with purple tint) corolla with strongly reflexed segments.     

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.     

Hoya amicabilis sp. nov. (Apocynaceae,Asclepiadoideae), from Java discovered on Facebook

A new species from Java, Hoya amicabilis S.Rahayu & Rodda is described and illustrated. It was first identified as a new species from pictures posted on social media in 2017. Hoya amicabilis is part of a small group of species that have an unusual shrubby habit, but it is the only one in that group with bright yellow campanulate flowers. Furthermore, Hoya amicabilis is a rather unusual species of Hoya since its staminal corona lobes are oblong, erect, while most species of Hoya have well‐developed generally spreading corona lobes, and its style head is umbonate, brightly coloured and extending above the anther appendages, while most species have a conical style head covered by anther appendages.     

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.     

Hoya peninsularis (Apocynaceae,Asclepiadoideae), a new species from Peninsular Malaysia,and notes on Hoya maingayi and Gongronema wrayi

A new species of Hoya from the western part of Peninsular Malaysia is described and illustrated as H. peninsularis. It has long been confused with Hoya finlaysonii because both have leaves with prominent darker venation, but can be distinguished on the corona lobe size and corolla pubescence. In addition, Hoya maingayi, a species earlier considered ‘doubtful and excluded' is typified and illustrated for the first time, and its distribution is shown to extend to Thailand. Gongronema wrayi is recognised as an earlier name and a new synonym for Hoya omlorii, a species previously considered to occur only in Borneo and Sumatra. The name is typified. An updated checklist of Hoya of Peninsular Malaysia is provided.     

Caralluma bicolor sp. nov. (Apocynaceae,Asclepiadoideae) from India

Caralluma bicolor Ramach, S. Joseph, H. A. John & C. Sofiya sp. nov. (Apocynaceae) collected from Coimbatore, Tamil Nadu in India is described and illustrated. Morphological differences between the new species and the allied species C. adscendens (Roxb.) Haw. and C. sarkariae Lavranos & Frandsen are discussed.     

Ceropegia pullaiahii sp. nov. (Apocynaceae,Asclepiadoideae) from India

Ceropegia pullaiahii Kullayiswamy, Sandhyarani et Karuppusamy sp. nov. (Apocynaceae) is described from open dry deciduous forest of Anantapur district, Andhra Pradesh, India. Its tubers are eaten by the local people. It is similar to C. mahabalei Hemadri et Ansari but differs in its twining habit and 3‐flowered cyme.     

Hoya aphylla (Apocynaceae,Asclepiadoideae), a new leafless species from Laos

The leafless species Hoya aphylla Aver. N.S. Khang & Averyanova (Apocynaceae) is described and illustrated as a new species for science from Hin Nam No National Protected Area of Laos (central Laos, Khammoune province). In its floral morphology, this new species may be similar to H. lyi, H. carnosa and H. multiflora, but it differs in corona color and shape of corona segments. Like the first two mentioned species, the new species may be referred to the type section of the genus, but in terms of it its leafless habit it exhibits an isolated position.     

Ceropegia thaithongiae sp. nov. (Apocynaceae,Asclepiadoideae) from northern Thailand and preliminary observations on impacts of climate change on its only known population

A new pendulous herb, Ceropegia thaithongiae Kidyoo (Apocynaceae, Asclepiadoideae), is described from northern Thailand. This plant is strictly endemic to Chiang Dao Wildlife Sanctuary and critically endangered owing to it living in an ecosystem affected by frequent natural disturbances. It is here described, illustrated and compared to the similar species, C. mairei. Both species have fusiform rootstocks, 1–2‐flowered cymes, deeply bifid outer corona lobes and linear, hairy inner corona lobes. However, the new species can be distinguished by its glabrous stem, leaf covered with hairs on both surfaces and glabrous corolla tube and lobes.     

Gymnemopsis phuwuaensis (Apocynaceae,Asclepiadoideae), a new species from northeastern Thailand

A new species, Gymnemopsis phuwuaensis A. Kidyoo, has been discovered in northeastern Thailand and is here described and illustrated. An identification key to all species of the genus is provided. Photographs and a diagnostic comparison with the morphologically similar species G. calcicola Kerr, are also provided. Gymnemopsis phuwuaensis displays clear differences in form and color of the corolla as well as in size of bract and flower. A lectotype for Gymnemopsis pierrei is also designated.     

Corona and anther skirt in Hoya (Apocynaceae, Marsdenieae)

The so called revolute margins of the corona in the genus Hoya (Marsdenieae) are homologous to the anther skirt. The anther skirt is primarily formed of two latero-basal lobes of the anther. In Hoya these lobes are fused with the underside of the basal process of the staminal corona and have evolved into a dominant structure of the gynostegium. Embedded in the anther skirt is the nectar tube, formed by the basal elongation of the guide rail. In many species, however, the function of nectar secretion for pollinator reward has been transferred to the anther skirt beneath the basal process of the corona. A survey of the Marsdenieae shows that the potential for developing an anther skirt is present in several other genera as well, though nowhere has it evolved into such elaborated structures as in Hoya.     

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.     

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.