Hoya arnottiana
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| Wight |
Hoya arnottiana is a plant of the genus of wax flowers ( Hoya ) of the subfamily of asclepiadoideae (Asclepiadoideae).
features
Hoya arnottiana is an epiphytic and / or lithophytic , twining-climbing plant with two to four meter long shoots . The shoots attach themselves to the ground with adventitious roots . The slender shoots are dull light green to gray-green in color. Fresh shoots have brown-gray hairs on the surface, older shoots are glabrous and easily lignified. The shoots are round and measure 2.5 to 3 mm in diameter. The intermediate node areas are between 5 to 20 cm long.
The stalked leaves are cross opposite. The thick, dark green stems are covered with brown-gray hairs. The stems are 1.7 to 2 cm long and 2.5 to 3 mm thick. They are round in cross section and often curved upwards (negative geotropic ). The leaf blade is fleshy-thick and elliptical in outline. 8.5 to 10.5 cm long, and 3.5 to 6 cm wide. The base of the blade is wedge-shaped to rounded, the apex of the blade rounded to pointed. The top is dark green and shiny. The underside is whitish-green, with a fluff of brown-gray hairs. The central vein is developed as ribbed with visible secondary veins. The leaf margins are slightly rolled out. The leaves show a clear network nerve with four to five paired secondary veins.
The inflorescence is an umbel that attaches outside the leaf axils. The umbel has a hemispherical arched top and has up to 40 flowers. The light green, straight and stiff peduncle is covered with brown-gray hairs and slightly thickened at the base and end. It becomes 3.5 to 7 cm long, with a diameter of 2.5 to 3 mm in the thinner parts and 5.5 to 5.8 mm in the thicker parts. The slender flower stalks are whitish to light green and glabrous. They are 21.5 to 22.5 mm long and 0.8 to 1 mm thick.
The flowers are almost pure white to slightly creamy yellow (Kloppenburg). The calyx is flat with a diameter of 5.4 to 5.6 mm. It is sparsely haired with short hairs. The five yellowish-white sepals are fused at the base. They are narrow-egg-shaped to narrow triangular and pointed, 1.8 to 2.2 mm long, 1.3 to 1.7 mm wide at the base.
The hermaphrodite flower is radially symmetrical and five-fold. The corolla has a diameter of 1.65 to 1.75 cm. The white petals are curved and back. The edges and the apex are rolled up, the apex is pointed. They are rhomboid in shape and fused at the base. They measure 7.8 to 8.5 mm in length and 4.8 to 5.3 mm in width. The outside is bald, the inside has short downy hairs. The secondary crown is glossy white, occasionally with a light pink tint in the center. It measures 8.6 to 9 mm in diameter. The corolla lobes are obliquely elliptical in outline, the top is slightly recessed. They are 4.3 to 4.8 mm long and 2.4 to 2.7 mm wide. The outer extension is pointed, but ends in two unequal corners. The inner process is pointed briefly, it does not reach the apex of the gynostegium. There are five pollinaries on the gynostegium , covered by the membranous yellowish stamen processes .
The pollinarium consists of the very small, central corpusculum, only short and thin caudiculae ( translator arms ) and the paired, outer pollinia. When viewed from the side, the chestnut-brown corpusculum is a dragon square with an obtuse-angled lower end and an acute-angled upper end. Narrow wings are developed on the sides . The caudiculae are very short, only about 0.03 mm long. The yellowish pollinia are elongated, 0.6 to 0.7 mm long, 0.2 to 0.25 mm wide. The outer edge is widened like a wing, light yellow and translucent. The wings extend from the base of the caudiculae to the apex of the pollinia. The gynoeceum has two carpels . These have the shape of a lengthwise cut bottle. The two upper ends of the carpels incline towards each other. They are 1.4 to 1.5 mm high and 0.5 to 0.7 mm in diameter.
Geographical distribution and habitat
The range of the species stretches from Laos ( province Houaphan ), Vietnam (provinces Dak Lak and Thanh Hoa ). Thailand . Nepal , India ( Assam , Meghalaya , Sikkim and West Bengal ) and Bangladesh .
The species grows in evergreen tropical mountain forests at altitudes between 300 and 1550 m. In Laos (altitude 1,500 to 1,550 m above sea level) the species blooms from April to June. It grew there on basalt (Averyanov et al., 2017).
Taxonomy
The taxon was described by Robert Wight in 1834. The lectotype from Nepal is kept in the Robert Wight Proper Herbarium in Kew Gardens (London) under the number K000873110 (“Wallich, Asclep. No. 35.”). The lectotype was first introduced by Averyanov et al. (2017).
literature
- LV Averyanov, Van The Pham, TV Maisak, Tuan Anh Le, Van Canh Nguyen, Hoang Tuan Nguyen, Phi Tam Nguyen, Khang Sinh Nguyen, Vu Khoi Nguyen, Tien Hiep Nguyen, M. Rodda: Preliminary checklist of Hoya (Asclepiadaceae) in the flora of Cambodia, Laos and Vietnam. Turczaninowia, 20 (3): 103-147, 2017 doi : 10.14258 / turczaninowia.20.3.10
- Dale Kloppenburg, Ann Wayman: The World of Hoyas - a pictorial guide. A revised version. 248 pp. Orca Publishing Company, Central Point, Oregon, 2007 ISBN 0-9630489-4-5 (pp. 52/53).
- Anders Wennström and Katarina Stenman: The Genus Hoya - Species and Cultivation. 144 p., Botanova, Umeå 2008 ISBN 978-91-633-0477-4 (p. 27)
Individual evidence
- ^ Kew Science - Plants of the World online: Hoya arnottiana Wight
- ^ Robert Wight: Contributions to the Botany of India. 136 pp., Parbury, Allen & Co, London 1834. Online at Google Books