Apocynaceae

Alstonia R.Br.

First published in Asclepiadeae: 64 (1810), nom. cons.
This genus is accepted
The native range of this genus is Mexico to Central America, Tropical Africa to S. Pacific.

Descriptions

Timothy M. A. Utteridge and Laura V. S. Jennings (2022). Trees of New Guinea. Kew Publishing. Royal Botanic Gardens, Kew

Distribution
A genus of 43 species, distributed in Central America, tropical Africa and Asia from China and the Himalayas to northern Australia and the western Pacific. Nine species in New Guinea (five endemic), with three in the Solomon Islands.
Morphology General Habit
Trees and shrubs to 60 m tall, usually buttressed, base at least fluted, often with pagoda branching when young. Branchlets and inflorescence axis often pubescent
Morphology Leaves
Leaves in whorls of 3–9, petiolate or sessile, elliptic, lanceolate or oblanceolate, colleters present in the axils
Morphology Reproductive morphology Inflorescences
Inflorescence terminal, compound cymes or umbelliform, (few–)many-flowered
Morphology Reproductive morphology Flowers
Flowers 5-merous, usually fragrant; corolla tube longer than the lobes, pubescent inside the tube, salver-shaped, lobes twisted to the left or right; stamens included, anthers ovate, apex acute; disk present, annular; ovary superior, apocarpous, 2-carpellate, united by a common style. Fruit of paired linear follicles
Morphology Reproductive morphology Seeds
Seeds numerous, elliptic to oblong, ciliate, cilia longest at the ends.
Ecology
Alstonia are large canopy trees found in lowland areas especially secondary habitats including fallow gardens, forest regrowth and rain forest edges, but also in primary rain forest, montane forests, and Melaleuca/savannah grassland; from sea level to c. 2100 m.
Recognition
The genus can be recognised by the whorled leaves, pubescence on the branchlets, inflorescence axis and inner corolla tube, flowers with an annular disk and the fruit of paired, linear follicles. The latex is recorded as being abundant in young twigs/branchlets but scant or absent from the trunk; the leaves often dry flat (rather than ‘crinkling’ upon drying).
[TONG]

Apocynaceae, E.A. Omino. Flora of Tropical East Africa. 2002

Morphology General Habit
Trees or shrubs; branches verticillate, in whorls of 4–5
Morphology Leaves
Leaves verticillate or opposite (not in our area), petiolate, with or without intrapetiolar stipules which are often adnate to the petiole; colleters present in leaf axils
Morphology Reproductive morphology Inflorescences
Inflorescence terminal, thyrsoid or compound, subumbellate, in whorls of 1–5
Morphology Reproductive morphology Flowers
Flowers 5-merous, actinomorphic
Morphology Reproductive morphology Flowers Corolla
Corolla white, yellow or red; tube cylindrical, widened around anthers, thickened at the throat; lobes spreading, overlapping to the left
Morphology Reproductive morphology Flowers Androecium Stamens
Stamens included; anthers basifixed, introrse
Morphology Reproductive morphology Flowers Disc
Disk present, free or adnate to the ovary, often indistinct. Ovary 2-celled, apocarpous or syncarpous, ovules numerous, style terete, stigma bifid, subtended by a cylindrical or slightly conical clavuncula
Morphology Reproductive morphology Fruits
Fruit of two follicles, free or connate at the base
Morphology Reproductive morphology Seeds
Seeds numerous, pubescent, ciliate, sometimes winged.
[FTEA]

Sources

  • Flora of Tropical East Africa

    • Flora of Tropical East Africa
    • http://creativecommons.org/licenses/by-nc-sa/3.0

  • Herbarium Catalogue Specimens

    • 'The Herbarium Catalogue, Royal Botanic Gardens, Kew. Published on the Internet http://www.kew.org/herbcat [accessed on Day Month Year]'. Please enter the date on which you consulted the system.

  • Interactive Key to Seed Plants of Malesia and Indo-China

    • The Malesian Key Group (2010) Interactive Key to Seed Plants of Malesia and Indo-China (Version 2.0, 28 Jul 2010) The Nationaal Herbarium Nederland Leiden and The Royal Botanic Gardens Kew

  • Kew Backbone Distributions

    • The International Plant Names Index and World Checklist of Vascular Plants 2025. Published on the Internet at http://www.ipni.org and https://powo.science.kew.org/
    • © Copyright 2023 World Checklist of Vascular Plants. http://creativecommons.org/licenses/by/3.0

  • Kew Names and Taxonomic Backbone

    • The International Plant Names Index and World Checklist of Vascular Plants 2025. Published on the Internet at http://www.ipni.org and https://powo.science.kew.org/
    • © Copyright 2023 International Plant Names Index and World Checklist of Vascular Plants. http://creativecommons.org/licenses/by/3.0

  • Trees of New Guinea

    • Trees of New Guinea
    • http://creativecommons.org/licenses/by-nc-sa/3.0