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Isonema smeathmannii Roem. & Schult.

Protologue
Syst. veg. 4: 401 (1819).
Family
Apocynaceae
Chromosome number
2n = 22
Origin and geographic distribution
Isonema smeathmannii occurs in West Africa, from Senegal to Ghana.
Uses
In Sierra Leone young leaves of Isonema smeathmannii are eaten as a vegetable. In Côte d’Ivoire the Kyama people use the latex to treat old sores.
Botany
Climbing shrub up to 5 m tall, branches up to 20 m long, scarcely containing sticky clear or milky latex (most obvious in the roots); main stem c. 2 cm in diameter, branches blackish, branchlets rusty-brown pubescent. Leaves opposite, simple; petiole 3–7 mm long, pubescent; blade oblong to narrowly obovate, 4–12 cm × 2–5 cm, base usually rounded, apex acuminate to apiculate or obtuse, margin entire, leathery, pilose to pubescent beneath, secondary veins 4–6 on each side. Inflorescence usually terminal, thyrsoid, up to 27 cm × 6 cm, densely pubescent; peduncle up to 7 cm long. Flowers bisexual, regular, 5-merous; pedicel 3–5 mm long; sepals broadly ovate, 2–2.5 mm × 1–2 mm, brownish, pubescent outside, bearing 5 groups of 2–3 glands 1 mm long; corolla tube 7–10.5 mm long, glandular pubescent inside, lobes ovate-oblong, 4.5–6 mm × 2–3 mm, red-brown to pink-red inside and with 4 yellow longitudinal stripes, corolla often with lateral appendage; stamens exserted for 3–4.5 mm; ovary superior, consisting of 2 free carpels, style filiform, 8.5–12 mm long, club-shaped at apex and composed of 2 rings above each other, stigma 2-lobed. Fruit composed of 2 widely spreading follicles connate at base, each one cylindrical, 11–20 cm × 0.5–1 cm, velvety rusty brown, many-seeded. Seeds fusiform, laterally compressed, 18–22 mm × 2–3.5 mm, at apex bearing a coma of spreading hairs about 2 cm long.
Isonema is a small genus of 3 species, restricted to West and Central tropical Africa. The other 2 species are Isonema buchholzii Engl. (restricted to Nigeria and Cameroon) and Isonema infundibuliflorum Stapf (restricted to Cameroon, Gabon and DR Congo). The presence of unilateral appendages to the corolla distinguishes Isonema from related genera.
Ecology
Isonema smeathmannii grows in scrub vegetation or forest, mainly near the coast, often near water or in swampy locations. Flowering and fruiting has been observed year-round.
Genetic resources and breeding
In its area of distribution Isonema smeathmannii is rather common and not in danger of genetic erosion.
Prospects
Isonema smeathmannii is a decorative climbing shrub with red-yellow flowers. The value of its young leaves as a vegetable and its latex as a medicine can only be confirmed after more investigation.
Major references
• Burkill, H.M., 1985. The useful plants of West Tropical Africa. 2nd Edition. Volume 1, Families A–D. Royal Botanic Gardens, Kew, United Kingdom. 960 pp.
• Huber, H., 1963. Apocynaceae. In: Hepper, F.N. (Editor). Flora of West Tropical Africa. Volume 2. 2nd Edition. Crown Agents for Oversea Governments and Administrations, London, United Kingdom. pp. 51–80.
• van der Ploeg, J., 1983. A revision of Isonema R.Br. and Pycnobotrya Benth. (Apocynaceae). Mededelingen Landbouwhogeschool Wageningen Nederland 83(4). 20 pp.
Other references
• Bouquet, A. & Debray, M., 1974. Plantes médicinales de la Côte d’Ivoire. Travaux et Documents No 32. ORSTOM, Paris, France. 231 pp.
• Dalziel, J.M., 1937. The useful plants of west tropical Africa. Crown Agents for Oversea Governments and Administrations, London, United Kingdom. 612 pp.
• Irvine, F.R., 1961. Woody plants of Ghana, with special reference to their uses. Oxford University Press, London, United Kingdom. 868 pp.
Author(s)
P.C.M. Jansen
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands


Editors
G.J.H. Grubben
Prins Hendriklaan 24, 1401 AT Bussum, Netherlands
O.A. Denton
National Horticultural Research Institute, P.M.B. 5432, Idi-Ishin, Ibadan, Nigeria
Associate Editors
C.-M. Messiaen
Bat. B 3, Résidence La Guirlande, 75, rue de Fontcarrade, 34070 Montpellier, France
R.R. Schippers
De Boeier 7, 3742 GD Baarn, Netherlands
General editors
R.H.M.J. Lemmens
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands
L.P.A. Oyen
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands

Correct citation of this article:
Jansen, P.C.M., 2004. Isonema smeathmannii Roem. & Schult. In: Grubben, G.J.H. & Denton, O.A. (Editors). PROTA 2: Vegetables/Légumes. [CD-Rom]. PROTA, Wageningen, Netherlands.