Alstonia


Alstonia is a widespread genus of evergreen trees and shrubs, of the family Apocynaceae. It was named by Robert Brown in 1811, after Charles Alston, professor of botany at Edinburgh from 1716-1760.
The type species Alstonia scholaris R.Br. was originally named Echites scholaris by Linnaeus in 1767.

Description

Alstonia consists of about 40-60 species, native to tropical and subtropical Africa, Central America, southeast Asia, Polynesia and Australia, with most species in the Malesian region.
These trees can grow very large, such as Alstonia pneumatophora, recorded with a height of 60 m and a diameter of more than 2 m. Alstonia longifolia is the only species growing in Central America.
The leathery, sessile, simple leaves are elliptical, ovate, linear or lanceolate and wedge-shaped at the base. The leaf blade is dorsiventral, medium-sized to large and disposed oppositely or in a whorl and with entire margin. The leaf venation is pinnate, with numerous veins ending in a marginal vein. Phyllotaxy is whorled i.e. two or more leaves arises at a node and form a whorl.
The inflorescence is terminal or axillary, consisting of thyrsiform cymes or compound umbels. The small, more or less fragrant flowers are white, yellow, pink or green and funnel-shaped, growing on a pedicel and subtended by bracts. They consist of 5 petals and 5 sepals, arranged in four whorls. The fertile flowers are hermaphrodite. The gamosepalous green sepals consist of ovate lobes, and are distributed in one whorl. The annular disk is hypogynous. The five gamesepalous petals have oblong or ovate lobes and are disposed in one whorl. The corolla lobes overlapping to the left or to the right in the bud. The ovary has 2 separate follicles with glabrous or ciliate, oblong seeds that develop into deep blue podlike, schizocarp fruit, between 7–40 cm long. The plants contain a milky latex, rich in poisonous alkaloids. The Alstonia macrophylla is commonly known in Sri Lanka as 'Havari nuga' or the 'wig banyan' because of its distinct flower that looks like a woman's long wig.
Alstonia trees are used in traditional medicine. The bark of the Alstonia constricta and the Alstonia scholaris is a source of a remedy against malaria, toothache, rheumatism and snake bites. The latex is used in treating coughs, throat sores and fever.
Many Alstonia species are commercial timbers, called pule or pulai in Indonesia and Malaysia. Trees from the section Alstonia produce light timber, while those from the sections Monuraspermum and Dissuraspermum produce heavy timber.
Alstonia trees are widespread and mostly not endangered. However a few species are very rare, such as A. annamensis, A. beatricis, A. breviloba, A. stenophylla and A. guangxiensis.

Species

Alstonia has five distinct sections, each a monophyletic group; Alstonia, Blaberopus, Tonduzia, Monuraspermum, Dissuraspermum.
;Accepted species
  1. Alstonia actinophylla K.Schum. – milkwood - New Guinea, N Australia
  2. Alstonia angustifolia A.DC. - Borneo, W Malaysia, Sumatra
  3. Alstonia angustiloba Miq. - Borneo, W Malaysia, Sumatra, Thailand, Java
  4. Alstonia annamensis K.Sidiyasa - Cambodia, Vietnam
  5. Alstonia balansae Guillaumin - New Caledonia
  6. Alstonia beatricis K.Sidiyasa - Waigeo I in E Indonesia
  7. Alstonia boonei De Wild. - W + C + E Africa
  8. Alstonia boulindaensis Boiteau - New Caledonia
  9. Alstonia breviloba K.Sidiyasa - Papua New Guinea
  10. Alstonia congensis Engl. - W + C Africa
  11. Alstonia constricta F.Muell. – bitterbark, quinine tree, Australian fever bark - E Australia
  12. Alstonia coriacea Pancher & S.Moore - New Caledonia
  13. Alstonia costata R.Br. - S Pacific
  14. Alstonia curtisii King & Gamble - Thailand
  15. Alstonia deplanchei Van Heurck & Müll.Arg. - New Caledonia
  16. Alstonia guangxiensis D.Fang & X.X.Chen - Guangxi in China
  17. Alstonia iwahigensis Elmer - Borneo, Palawan
  18. Alstonia lanceolata Van Heurck & Müll.Arg. - New Caledonia
  19. Alstonia lanceolifera S.Moore - New Caledonia
  20. Alstonia legouixiae Van Heurck & Müll.Arg. - New Caledonia
  21. Alstonia lenormandii Van Heurck & Müll.Arg. - New Caledonia
  22. Alstonia longifolia Pichon - Mexico, Central America
  23. Alstonia macrophylla Wall. ex G.Don – batino, devil tree - S China, Sri Lanka, SE Asia, New Guinea
  24. Alstonia mairei H. Léveillé - S China, N Vietnam
  25. Alstonia muelleriana Domin – jackapple, leatherjacket, milky yellowwood - New Guinea, Queensland
  26. Alstonia neriifolia D.Don - Nepal, Sikkim, Bhutan
  27. Alstonia odontophora Boiteau - New Caledonia
  28. Alstonia parkinsonii Lakra & Chakrab. - Andaman Is.
  29. Alstonia parvifolia Merr. - Philippines
  30. Alstonia penangiana K.Sidiyasa - Penang Hill in Malaysia
  31. Alstonia pneumatophora Backer ex L.G.Den Berger - W Malaysia, Borneo, Sulawesi, Sumatra
  32. Alstonia quaternata Van Heurck & Müll.Arg. - New Caledonia
  33. Alstonia rostrata C.E.C.Fischer - Yunnan, Indochina, W Malaysia, Sumatra
  34. Alstonia rubiginosa K.Sidiyasa - Papua New Guinea
  35. Alstonia rupestris Kerr - Thailand
  36. Alstonia scholaris R.Br. – pali-mari, dita bark, bitter bark, milkwood, milky bean, milky pine, white cheesewood, scholar tree, blackboard tree - E + S + SE Asia, Papuasia, N Australia
  37. Alstonia sebusi Monach. - Yunnan, Bhutan, Assam, N Myanmar
  38. Alstonia spatulata Blume – hard milkwood, Siamese balsa - SE Asia, New Guinea
  39. Alstonia spectabilis R.Br. – poele bark, jackapple, leatherjacket, milky yellowwood - SE Asia, Papuasia, N Australia
  40. Alstonia sphaerocapitata Boiteau - New Caledonia
  41. Alstonia venenata R.Br. - S India
  42. Alstonia vieillardii Van Heurck & Müll.Arg. - New Caledonia
  43. Alstonia vietnamensis D.J.Middleton - Vietnam
  44. Alstonia yunnanensis Diels - Yunnan, Guizhou, Guangxi

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