Mezoneuron Desf., Mem . Mus. Hist. Nat. 4: 245. 1818

Gagnon, Edeline, Bruneau, Anne, Hughes, Colin E., de Queiroz, Luciano Paganucci & Lewis, Gwilym P., 2016, A new generic system for the pantropical Caesalpinia group (Leguminosae), PhytoKeys 71, pp. 1-160 : 49-51

15. Mezoneuron Desf., Mem. Mus. Hist. Nat. 4: 245. 1818 Figs 24D-F, I , 25

Mezonevron Desf. and Mezoneurum DC. (1825), (orth. vars.).

Caesalpinia subg. Mezoneuron (Desf.) Vidal ex Herend. & Zarucchi (1990).

Type.

Mezoneuron glabrum Desf. ≡ Mezoneuron pubescens Desf.

Description.

Scrambling shrubs or lianas, occasionally medium -sized trees ( Mezoneuron kauaiense ) to 12 m, usually armed with recurved prickles on stem and leaves, rarely unarmed. Stipules very small, often caducous. Leaves alternate or occasionally opposite, bipinnate, ending in a pair of pinnae; pinnae opposite to sub-opposite, in (1-)2-18 pairs; leaflets opposite to alternate, in 1-15 pairs per pinna, elliptic, oblong, suborbicular to occasionally subrhombic, the base oblique, the apex obtuse to acute. Inflorescences terminal or axillary racemes (often aggregated into panicles); bracteoles small. Flowers bisexual, zygomorphic; calyx comprising a hypanthium and 5 imbricate sepals, the lower sepal cucullate, and overlapping the other 4 in bud; petals 5, free, usually yellow with red markings on the median petal, or occasionally red, pink or cream, the median petal somewhat modified (either with a fleshy ligule or a patch of hairs on the inner surface between the blade and claw, or the petal bilobed); stamens 10, free, filaments alternately longer and shorter, usually all 10 pubescent or villous on lower half, or one or all glabrous; ovary glabrous to hairy, 1-many ovuled, stigma cupular, funnel-shaped, terminal or laterally placed, glabrous, or the rim fimbriate with papillate hairs, not peltate. Fruit laterally compressed, indehiscent, chartaceous, coriaceous or woody, venose, longitudinally and often broadly winged along the upper suture, the wing 1-18 mm wide. Seeds 1-13 per pod, ± transversely arranged in seed chamber, compressed, endosperm lacking.

Geographic distribution.

A genus of 24 extant species, mainly in Asia, extending to Australia, Polynesia, Madagascar and Africa; two species on mainland Africa (one widespread in West Africa, the other in both West, East and Southeast Africa); one endemic to Madagascar; five endemic to New Caledonia; one endemic in Hawaii; one in Vietnam; four endemic to Australia (Queensland and New South Wales); one endemic in the Philippines; one in Australia and Papua New Guinea; nine species more widespread across Asia.

Habitat.

Tropical and subtropical riverine forest, lowland rain forest, swamp forest, seasonally dry forest, thicket, vine forest and wooded grassland, especially along forest and river margins.

Etymology.

From meso - (Greek: middle) or meizon (Greek: greater) and neuron (Greek: nerve), the upper suture of the fruit is bordered by a usually broad longitudinal wing so that the suture appears as a prominent sub-central nerve or vein.

Notes.

The genus has recently been revised by Clark (2016), who provides full synonymy, a key to species, and a list of fossil taxa associated with this genus.

References.

Brenan (1967: 38-40); Hattink (1974); Vidal and Hul Thol (1976); Verdcourt (1979: 18-20); Lock (1989: 25); Herendeen and Zarucchi (1990); Pedley (1997); George (1998: 59-67); Wagner et al. (1999); Du Puy and Rabevohitra (2002: 48-49); Brummitt et al. (2007); Clark and Gagnon (2015); Clark (2016).

Figures

Figure 24. Pterolobium stellatum (Forssk.) Brenan. A inflorescences (P. van Wyk, Africa, unvouchered) B fruits (J. Anton-Smith, Africa, unvouchered) C close up of fruits (B. T. Wursten, Flora of Zimbabwe (http: // www. zimbabweflora. co. zw / speciesdata / image-display. php? species _ id = 127190 & image _ id = 1), Zimbabwe, unvouchered). Mezoneuron hildebrandtii Vatke D inflorescences (D. Du Puy, Majunga, Madagascar, Du Puy M 286 (P )) E fruits (D. Du Puy, Antsiranana, Madagascar, Du Puy M 273 (P )). Mezoneuron kauaiense (H. Mann) Hillebr. F flower and buds I fruit (D. Eickhoff, Wikicommons (https: // commons. wikimedia. org / wiki / Category: Mezonevron _ kavaiense) cultivated, Hawaii, U. S. A., unvouchered). Caesalpinia crista L. emend. Dandy & Exell (? Ticanto) G flowers H young fruits (P. Grard: Institut Francais de Pondichery, Andhra Pradesh, India, unvouchered).

Figure 25. Mezoneuron scortechinii F. Muell. A flowering branch B bract C calyx opened out D median petal E upper lateral petal F lower lateral petal G stamen H gynoecium I stigma J fruit K seed L detail of prickle from leaf. A-I, L from Hoogland 11665 J from Thurtill & Coveny 3880 K from White s. n. 6 / 1926. Drawn by Eleanor Catherine.