Hoya slender and glabrous with white latex. The

Hoya wongii is a lactiferous climbing plant that inhabits the Kerangas (Bornean heath) forest of Brunei Darussalam at 15 to 30 m above sea level. This type of forest ecosystem is a seasonal lowland tropical rain forest that are formed in areas of drylands with predominantly podzolized, strong acidic, sandy soils (Hazimah Din et al., 2015). It was discovered recently in 2011 at Tutong White Sand, Brunei Darussalam and was named after its first collector Dr Wong Khoon Meng who had contributed an immense knowledge with regards to the flora of Southeast Asia. Hoya wongii is listed as an endemic plant to Brunei Darussalam because it has not been recorded in other areas of Borneo (Rodda et al, 2011). However, the level of endemicity is difficult to assess as most hoya species since new descriptions are often based on single gatherings for species like Hoya wongii (Rodda and Simonsson, 2011).   Hoya wongii can be described as an epiphytic vine that is semi-woody, slender and glabrous with white latex. The leaf stem of this species can measure from 2.5 to 3 mm in diameter while older stems are seen as leafless. Hoya wongii attaches itself upon barks that are waxy and the distance of the internodes is between 15 to 150 mm with no presence of adventitious roots. The leaf arrangement of Hoya wongii is opposite and petiolate (having stalk or petiole). The length and width of the petiole can be 3 to 7 by 0.7 to 1.2 mm. The lamina of this species is coriaceous (resembling leather), flexible, not succulent and elliptic in shape. The lamina measurement is 50 to 90 mm by 20 to 40 mm whereby its central portion of the leaf appears to be the widest. The apex of the leaf is apiculate to cuspidate while the base is shortly attenuate. The margin of leaf is entire and penni-nerved. The main vein of the leaf is depressed on adaxial surface while evident on the abaxial surface. Hoya wongii is 1 flowered and the flowers are arranged in pseudo-umberlliform. The peduncle is extra-axillary, perennial with a length of 10 mm long and glabrous pedicels of 15 to 20 by 0.4 to 1 mm measurement. The calyx is about 5 mm diameter, sepals oblong about 2 by 1.6 mm, rounded apex with margins ciliate. The corolla is usually campanulate and pale yellow in color, 25 to 30 mm diameter. The corolla lobe is fused for 16 by 18 mm while the free lobes are 5 mm long with acute tips. The corona staminal pale yellow, with height of 5 to 6 mm high, 6 mm diameter, outer processes broadened into a rounded free process with revolute lateral margins, inner processes laterally compressed, ending in two bidentate membranous appendages, about 2 mm higher than outer processes and 0.3 mm higher than inner processes. The anther skirt is revolute and free from the filament tubes. The guide rail forms a ridge and is laterally compressed, prominent at the base of the anther skirt and extending 0.3 to 0.5 mm laterally. The pollinarium 1 mm long, pollinia oblanceolate, 830 by 300 um, rounded to obtuse apex, retinaculum 280 by 180 um, caudicles 120 um long. The ovary rounded and 2.5 mm long. The fruits and seeds are not seen (Rodda et al., 2011).   Hoya wongii should be listed as Data Deficient (DD) according to IUCN Red list criteria (IUCN 2001) because it is only known from one collection hence remain in need of further exploration with respect to future conservation efforts. This species were found in Kerangas forest, a nutrient deficient habitat rarely used for cultivation. The felling and burning activities of trees may degrade kerangas into an open savanna of shrubs making it inhospitable for many epiphytic plant species including Hoya. 


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