Mezoneuron sumatranum (Roxburgh) Wight & Arnott ex Voigt

Clark, Ruth P., 2016, A Taxonomic Revision of Mezoneuron (Leguminosae: Caesalpinioideae: Caesalpinieae), Phytotaxa 274 (1), pp. 448-450 : 448-450

8. Mezoneuron sumatranum (Roxburgh) Wight & Arnott ex Voigt

Hort. Suburb. Calcutt. 245. 1845.

Type:— SUMATRA, Campbell, C. s.n., 1797. Specimen untraced .

Basionym:— Caesalpinia sumatrana Roxb. Hort. Beng. : 32. 1814. nom. nud.; Fl. Ind. 2: 366. 1832. Synonym. M. sulfureum Miq. Fl. Ind. Bat. 1(1): 1081. 1855.

Type:— JAVA, Zollinger 1002. Holotype U; isotypes BM!, K (K000264164!), P!.

Synonym. M. koordersii Backer ex Koorders-Schumacher. Syst. Verz. i. Fam. 128, 36. 1911.

Type: JAVA: Koorders 34442. Holotype BO; isotype L.

Synonym. M. peekelii Harms. Bot. Jahrb. 55: 58. 1917.

Type: PAPUA NEW GUINEA, New Ireland, Peekel 453 (location of specimen unknown) .

Woody climber or scandent shrub to 20 m in length. Stems usually with scattered recurved prickles to 5 mm; glabrous, or sparsely whitish puberulous. Stipule flat or raised, oblong, sometimes with acuminate apex, 1–2 × 3–6 mm. Leaves with 4–7 [–8] pairs pinnae; 2–6 pairs leaflets per pinna; petioles 4.5–14 cm; leaf rhachis 21–43 [–50] cm, unarmed, or with recurved prickles paired at pinna insertion points and scattered on the internodes; pinnae opposite to subopposite, 7–16 cm, pinna rhachis sometimes with recurved prickles paired at leaflet insertion points and sometimes scattered on the internodes; leaf rhachis, petiole, and pinna rhachis all glabrous to sparsely pubescent, with short, erect, pale orange hairs. Leaflets alternate to subopposite; the terminal leaflets obovate, oblong, ovate, elliptic, or rhomboid, base oblique, apex rounded to retuse, 2.9–6.4 [–7] × 1.6–3.9 [–5.5] cm; lateral leaflets oblong to ovate to elliptic to rhomboid, base oblique, apex rounded to retuse, 2.8–5.2 × 1.2–3.3 cm; all leaflets with upper surface glabrous to very sparsely pubescent, lower surface glabrous to sparsely pubescent, with pale orange, erect hairs, often denser on midvein; 2˚ venation anastomosing, 3˚ venation reticulate, veins slightly raised above and below. Inflorescence a raceme to few-branched panicle, supra-axillary or terminal, up to 1.1 m long, the axis to 1 cm diameter at base; glabrous, or sparsely orange tomentose; pedicels not articulated, 10–15 mm (– 37 in fruit); glabrous. Bracts persistent, occasionally present at base of racemes, oblong, c. 0.75 × 1.5 mm; bracteoles caducous, broadly elliptic, tapering to acute apex, 1.5–2 × 0.75–1 mm, sparsely ferrugineous tomentose. Flowers with a hypanthium [3–] 5–8 × 4–12 mm, glabrous; lower calyx lobe 4–14 × 3–8 mm, other lobes [2–] 3–7 × 2–10 mm, all lobes with few hairs on margins, otherwise glabrous. Median petal blade obovate to orbicular, claw sometimes inrolled, petal 14–33 mm long, claw 7–21 mm, blade 7–12 × 7–17 mm; glabrous. Upper lateral petals narrowly obovate, claw attenuate to blade, 15–36 × 5–15 mm, glabrous. Lower lateral petals narrowly obovate, claw attenuate to blade, 12–33 × 3–11 mm, glabrous. Stamen filaments flattened, (9–) 13–37 mm long, 0.5–2.5 mm wide, glabrous; anthers (0.5–) 1–3.5 mm. Ovary 3–10 [–15] mm long, style [6–] 13–21 mm long, both glabrous; stigma cupular, ca. 0.5 mm wide, the rim papillate. Fruit elliptic, base obtuse, apex with the wing or central vein extending to form a beak; 9–19 × 3–6 cm, the wing arising basally ca. 2–4 mm along the central vein, wing 6–18 mm wide; fruit surface glabrous; venation reticulate, raised, and clearly visible on fruit body, anastomosing and faintly visible on the wing; widest part of the persistent, asymmetric hypanthium below the main body of the fruit. Seeds 3–8 per fruit; in outline oval and visible on fruit exterior when mature, perpendicular to central vein, ca. 10 × 7 mm, mid brown, smooth, with linear fissures.

Distribution:—Malay Peninsula, Borneo, Sumatra, Java, Papua New Guinea, Solomon Islands, New Britain. ( Fig. 9 ).

18 • Phytotaxa 274 (1) © 2016 Magnolia Press

CLARK

Habitat and ecology:—Primary and secondary rainforest. Limestone or granite substrate. To 1000 m elevation.

Phenology:—Flowering January–September, fruiting January–October.

Preliminary conservation assessment:—Extent of Occurrence 7,674,670.082 km 2 = LC; Area of Occupancy 132.000 km 2 = EN.

Category assigned:—Least Concern (LC).

Field notes:—Petals pink-red.

Figures

FIGURE 9. Distribution of M. sumatranum in South East Asia.