Alstonia

Alstonia consists of about 40–60 species (according to different authors) 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 (mainly shrubs, but also trees 20 m high).

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 (such as A. rostrata) or to the right (such as A. macrophylla) 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. Fijians use the latex of A. costata (saurua, sorua) as a form of chewing gum.[2] 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 Alstonia constricta and Alstonia scholaris is the 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 harvested for timber, called pule or pulai in Indonesia and Malaysia. Trees from the section Alstonia produce lightweight 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.

Alstonia has five distinct sections, each a monophyletic group; Alstonia, Blaberopus, Tonduzia, Monuraspermum, Dissuraspermum.

Accepted species[1]

1. Alstonia actinophylla (A.Cunn.) 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 (Monach.) 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 (A.DC.) 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 (M.Gangop. & Chakrab.) 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 (L.) 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 sebusii (Van Heurck & Müll.Arg.) 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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  Alstonia scholaris
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  Alstonia spectabilis
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  Alstonia macrophylla

Wikimedia Commons has media related to Alstonia.

• Kade Sidiyasa (1998). "Taxonomy, phylogeny, and wood anatomy of Alstonia (Apocynaceae)". Blumea. Supplement. 11: 1–230. ISBN 90-71236-35-8
• Kade Sidiyasa, A., 3, 1992. A monograph of Alstonia (Apocynaceae).
• Forster, P.I. (1992). "A taxonomic revision of Alstonia (Apocynaceae) in Australia". Australian Systematic Botany. 5 (6): 745. doi:10.1071/SB9920745. ISSN 1030-1887.