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Pyranthus alasoa Du Puy & Labat

Protologue
Kew Bull. 50(1): 78, fig. 1 A–F (1995).
Family
Papilionaceae (Leguminosae - Papilionoideae, Fabaceae)
Origin and geographic distribution
Pyranthus alasoa is known to occur in two small areas in central and western Madagascar, one south of Ihosy and the other east of Morondava.
Uses
The wood is used for beams and posts in house building. A leaf infusion is drunk to treat stomach complaints.
Properties
The wood is hard and durable.
Botany
Deciduous shrub or small tree up to 6 m tall; bole up to 20 cm in diameter; inner bark bright yellow; young twigs densely hairy, pale grey or yellowish. Leaves alternate, imparipinnately compound with 15–25(–29) leaflets; stipules slender, linear-triangular; petiole and rachis densely whitish or yellowish hairy; leaflets opposite or alternate, narrowly oblong, (1.5–)2–3(–3.5) cm × 0.5–1.5 cm, rounded at base, rounded and mucronate at apex, thinly leathery, glabrescent above, densely silky silvery hairy below. Inflorescence an axillary or terminal false raceme, long and lax, with flowers solitary or in pairs. Flowers bisexual, papilionaceous; pedicel c. 0.5 cm long; calyx cup-shaped, 3–5 mm long, 5-toothed with 2 upper teeth partially fused, densely hairy; corolla scarlet-red, standard circular, 13–17 mm in diameter, with whitish basal spot, wings and keel about as long as standard, curved; stamens 10, filaments fused for most of their length, curved; ovary superior, 1-celled, style curved, stigma minute. Fruit a linear-oblong pod 6–11 cm long, flattened, slightly upcurved, densely hairy, pale brown, splitting into 2 spiralling valves, 6–10-seeded. Seeds kidney-shaped, c. 5 mm long, flattened, pale brown.
Pyranthus alasoa flowers on new shoots, often developing from thick woody stems after grassland fires.
Pyranthus comprises 6 species and is endemic to Madagascar. It is classified in the tribe Millettieae and is somewhat intermediate between the related genera Mundulea and Chadsia.
The wood of Pyranthus lucens (R.Vig.) Du Puy & Labat is used for similar purposes as that of Pyranthus alasoa. This species is a shrub occurring in western Madagascar, and differs in its distinctly channelled leaf rachis, glossy leaflets and sparsely hairy pods. Pyranthus alasoa is also related to Pyranthus tullearensis (Baill.) Du Puy & Labat, of which the bark is used for colouring the skin yellow in south-western Madagascar and which differs in slightly smaller leaflets and flowers.
Ecology
Pyranthus alasoa occurs in open grassland and remnants of woodland up to 1000 m altitude, on lateritic soils. It is resistant to fires.
Genetic resources and breeding
Pyranthus alasoa has a limited area of distribution consisting of two disjunct populations, but is not immediately threatened because it is adapted to regularly burned grassland.
Prospects
Although Pyranthus alasoa tolerates fires, regular burning will negatively affect bole size and thus wood production.
Major references
• du Puy, D.J., Labat, J.N., Rabevohitra, R., Villiers, J.-F., Bosser, J. & Moat, J., 2002. The Leguminosae of Madagascar. Royal Botanic Gardens, Kew, Richmond, United Kingdom. 750 pp.
Other references
• du Puy, D.J. & Labat, J.N., 1995. Pyranthus Du Puy & Labat, a new genus of the tribe Millettieae (Leguminosae-Papilionoideae) from Madagascar. Kew Bulletin 50: 73–84.
• Jansen, P.C.M., 2005. Pyranthus tullearensis (Baill.) Du Puy & Labat. In: Jansen, P.C.M. & Cardon, D. (Editors). Plant Resources of Tropical Africa 3. Dyes and tannins. PROTA Foundation, Wageningen, Netherlands / Backhuys Publishers, Leiden, Netherlands / CTA, Wageningen, Netherlands. pp. 135–136.
• Schatz, G.E., 2001. Generic tree flora of Madagascar. Royal Botanic Gardens, Kew, Richmond, United Kingdom. 477 pp.
Author(s)
R.H.M.J. Lemmens
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands


Editors
D. Louppe
CIRAD, Département Environnements et Sociétés, Cirad es-dir, Campus international de Baillarguet, TA C-DIR / B (Bât. C, Bur. 113), 34398 Montpellier Cedex 5, France
A.A. Oteng-Amoako
Forestry Research Institute of Ghana (FORIG), University P.O. Box 63, KNUST, Kumasi, Ghana
M. Brink
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, 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
J.R. Cobbinah
Forestry Research Institute of Ghana (FORIG), University P.O. Box 63, KNUST, Kumasi, Ghana

Correct citation of this article:
Lemmens, R.H.M.J., 2007. Pyranthus alasoa Du Puy & Labat. In: Louppe, D., Oteng-Amoako, A.A. & Brink, M. (Editors). Prota 7(1): Timbers/Bois d’œuvre 1. [CD-Rom]. PROTA, Wageningen, Netherlands.