Hoya bakoensis
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Hoya bakoensis is a plant of the genus of wax flowers ( Hoya ) of the subfamily of asclepiadoideae (Asclepiadoideae).
features
Hoya bakoensis is a small, epiphytic , climbing plant with slender, slightly twisting shoots. The dull green shoots have a diameter of 0.7 to 1.5 mm (rarely up to 2 mm). Fresh shoots are sparsely hairy, older shoots are scaly. Aerial roots are only sparsely formed along the shoots and under the nodes. The internodes are 2 to 7 cm (rarely 10 cm) long. The leaves are stalked, the sparsely hairy petioles are straight or curved, and 4 to 10 mm long and 1 to 1.5 mm thick. They are dark green to brownish and sparsely hairy. The leaf blades are ovate to, more rarely, lanceolate, 1.5 to 5 cm long and 1 to 2.8 cm wide. The base is pointed, the apex pointed. The top is dark green, the bottom is a little lighter. The edges and the midrib can be a little darker. Fresh leaves are sparsely hairy, older leaves are glabrous. The edges of some leaves can be covered with cilia. Only the midrib is clearly visible, the secondary veins can only be seen indistinctly. At the base of each leaf is a triangular to ovoid gland, 0.1 to 0.3 × 0.3 to 0.5 mm. All vegetative parts of the plant release a white milky sap when damaged.
The umbel-shaped inflorescence has 10 to 15 flowers and is slightly curved on top. The diameter is about 1 to 1.5 cm. The peduncle is 4 to 6 cm long, with a diameter of 1 to 1.5 mm. It is dull green to brownish and downy hairy. The flower stalks are 3 to 7 mm, with a diameter of 0.7 to 0.9 mm. They are pale green with pink spots and papilose. The sepals are triangular and 0.7 to 1 mm long and 0.5 to 0.8 mm wide at the base. The apex is pointed or round. They are light green with pink edges and sparsely covered with cilia. In each sinus between the sepals there is an egg-shaped gland (dimensions: 150–200 × 80–100 µm). The corolla is strongly bent. It has a diameter of 3.5 to 4 mm or approx. 6 mm when spread out. The petal lobes are fused at the base (basal 1.2 to 1.5 mm), the free lobes are triangular, 2 to 3 long and 2.4 to 2.7 mm wide. They are pink in color, hairy on the inside and bare on the outside. The staminal secondary crown has a diameter of 2.8 to 3 mm and is 0.9 to 1.1 mm high. The corolla lobes are elongated, 1.2 to 1.4 mm long and 0.7 to 0.8 mm wide. They are convex at the top, with a longitudinal groove and rolled edges at the bottom. The outer, light yellow extension is split (bifid), the inner, reddish extension is elongated with a yellow round end. The anthers are broadly triangular 400 to 450 high and 550 to 650 µm wide with a membranous appendix. The pollinia are club-shaped, 200 to 250 µm long and max. 90 to 110 µm wide; they become narrower towards the base. The apex slopes inwards. They have a transparent edge on the outside. , The corpusculum is elongated and constricted in the middle. It is 80 to 100 µm long (high) and 50 to 60 µm wide. The caudiculae are broad, spatulate and translucent, 110 to 130 µm long and 30 to 45 µm thick (wide). The stylus head is pentagonal in cross-section, the apex is round. It has five lobes that alternate with the stems. The stylus head is 200 to 300 µm long (high) and measures approx. 0.5 mm in cross section at the base. The light green ovary is egg-shaped with a narrow tip, 0.8 to 1 mm high, each carpel is about 0.3 mm wide at the base. A still unripe fruit was linear, 10 cm long and measured only 2 mm in cross section. The immature seed was lanceolate, 3 to 4 mm long with side wings and a long mop of hair.
Similar species
Hoya bakonensis is similar to Hoya aeschynanthoides Schltr., Both species have split outer secondary crown processes. They differ in the size and color of the corolla and corolla. In Hoya bakoensis , the pink corolla measures 3.5 to 4 mm in diameter, the corolla lobes are red and yellow. In Hoya aeschynanthoides , the white corolla measures approx. 5 mm in diameter. Hoya aeschynanthoides is more of a creeping than a climbing species, whereas Hoya bakoensis is a slightly twisting, climbing species.
Hoya bakoensis is divided into the Hoya section Acanthostemma (Blume) Kloppenb., Which is characterized by strongly backward curved petal lobes, double-lobed outer corolla processes and broad, spatulate caudiculae.
Although the flowers of Hoya pubera are comparable in size to the flowers of Hoya bakoensis , they are yellowish-orange and the petal tips are only rolled up apically and the corolla is more clearly lifted out of the corolla. Hoya minutiflora has even smaller flowers, only 2.6 to 2.8 mm in diameter.
Geographical distribution and habitat
Hoya bakoensis is only known from Bako National Park in the Malaysian state of Sarawak (Borneo). Here it is common along the Tajor Trail in moist, shady Kerangaheide forests near a river and near the sea. The species only grows epiphytically and grows preferentially in rotted tree stumps from ant nests.
Taxonomy
The taxon was described by Michele Rodda in 2015 . The type specimen was collected on March 20, 2015 by Michele Rodda along the Tajor Trail in Bako National Park ( Sarawak , Borneo , Malaysia ). The holotype is kept in the herbarium of the Singapore Botanic Gardens under the number Rodda M MR1042b. Isotypes are located in the herbaria of the Department of Forestry in Kuching (Sarawak, Malaysia) and the Forest Research Institute Malaysia in Kepong ( Selangor , Malaysia).
The species is named almost self-explanatory after its place of discovery in Bako National Park (Sarawak, Malaysia). It is accepted as a valid taxon online by Plants of the World .
literature
- Anthony Lamb, Michele Rodda (with contributions by Linus Gokusing, Steven Bosuang and Sri Rahayu): A Guide to the Hoyas of Borneo. Natural History Publications (Borneo), Kota Kinabalu, 2016 ISBN 978-983-812-170-5 , pp. 42/43.
- Michele Rodda: Two new species of Hoya R.Br. (Apocynaceae, Asclepiadoideae) from Borneo. PhytoKeys, 53: 83-93, 2015 doi : 10.3897 / phytokeys.53.5079
- Michele Rodda: Index of names and typus of Hoya (Apocynaceae: Asclepiadoideae) of Borneo. Gardens' Bulletin Singapore, 69 (1): 33-65, 2017 doi : 10.3850 / S2010098116000039 , here p. 35.