Mezoneuron baudouinii, Guillaumin

Clark, Ruth P. & Gagnon, Edeline, 2015, A revision of Mezoneuron (Leguminosae: Caesalpinioideae) in New Caledonia, with perspectives on vegetation, geology, and conservation, Phytotaxa 207 (1), pp. 68-92 : 72-75

M. baudouinii Guillaumin

Contribution à la Flore de la Nouvelle-Calédonie. Bulletin du Muséum National d’Histoire Naturelle 31: 482. 1925.

Lectotype (here designated):— NEW CALEDONIA: Nouméa, Pancher 176, P (P00379673!); isolectotypes:—P (P00379675!, P00379674!)

Remaining syntypes:— NEW CALEDONIA: Nouméa, Baudouin 249, P (P00751918!)

Scrambling shrub, becoming lianescent, to c. 5 m. Stems with scattered small recurved prickles, older stems with corky spine-tipped tubercles, sparsely to moderately whitish to ferruginous tomentose. Stipules semi-caducous, triangular, 0.5–2 × 0.5–2 mm, glabrous to densely tomentose. Leaves bipinnate, rhachis unarmed (especially older leaves), or with small recurved prickles in pairs at the pinna insertion points, and sometimes scattered on the internodes; pinnae (4–) 5–11 opposite pairs, paripinnate; leaflets opposite, sometimes subopposite on lower parts of pinna, (3–) 5–15 pairs per pinna; petioles 2–7.5 cm; rhachis (6–) 9–25 cm; pinnae (2–) 3–7.5 (–9) cm; leaf rhachis and pinna rhachis glabrous or sparsely to moderately tomentose with whitish to ferruginous hairs. Leaflets oblong, strongly oblique at base, apex obtuse to slightly emarginate; terminal leaflets 0.7–2.2 × 0.4–1.2 (–1.7) cm; median laterals 1–2.3 × 0.4–1.5 cm; midvein usually excentric, slightly diagonal, impressed above, slightly raised below, secondary veins reticulate, anastomosing, faintly to clearly visible; glabrous on both surfaces, or sometimes with few ferruginous hairs on lower midvein, on upper or lower surface. Inflorescence a panicle, usually few-branched, axillary or terminal, 9–20 cm long, glabrous, or very sparsely, occasionally densely, white to ferruginous tomentose on the axes, hairs sometimes only at pedicel insertion points. Pedicels 2–8 mm, articulated 1–2 mm below calyx. Bracts sometimes singly at base of racemes, triangular, 1–2 × 0.5 mm, moderately to densely orange tomentose; bracteoles singly at base of pedicels, caducous, 1–1.5 × 0.5–1 mm, lanceolate to elliptic, apex acute, inrolled, sparsely to moderately ferruginous tomentose. Hypanthium c. 1mm deep, usually glabrous, occasionally moderately ferruginous tomentose; lower calyx lobe c. 5 × 3 mm, other lobes c. 4 × 2 mm, all glabrous. Median petal (3–) 4–6 × 2–2.5 mm, with a circular patch of dense, dark ferruginous hairs on inner surface where claw and blade meet, and hairs on margins of claw, outer surface glabrous; upper lateral petals 4–5 × 2–2.5 mm; lower laterals 4–5 × 2–3 mm; all laterals with blade glabrous, claw very sparsely ferruginous tomentose on inner surface. Stamens 10, filaments 3–6 mm long, densely ferruginous tomentose on lower half. Ovary 1–1.5 mm long, densely ferruginous pubescent, style 2–3 mm, glabrous, or ferruginous pubescent on the lower to half of length or less; stigma funnel-shaped, the rim fimbriate. Fruit (3.4–) 4.2–6.4 × 2–3.5 cm, wing 3–5 mm, extending along upper ⅔ to whole fruit length, fruit surface glabrescent, sometimes with a few hairs at the base and on the margins. Seeds 1 per fruit, circular, flattened, 1–1.1 cm diameter, brown, smooth. ( Figure 2 , Figure 3)

Distribution:— Endemic to New Caledonia. Ile Art; Grand Terre, North and South Provinces, East to West.

( Figure 4 ) Habitat:— Occurs in wet forest, or maquis (Appendix 2), on ultramaphic soil. Elevation 0– 400 m. Phenology:— Flowering December to July, fruiting June to August. Preliminary Conservation Assessment:— Extent of Occurrence 11,469.543 km 2 = VU, Area of Occupancy

36.000 km 2 = EN

Category assigned:— Endangered

Rationale:— This species, which grows in both wet forest and maquis, can be considered to be Endangered due to the small AOO, low number (c. 6) of known populations, and the continuing threats to its habitat of wet forest or maquis. Threats include logging, clearing, mining, and fires.

Nomenclatural Notes:— The lectotype was selected for being the specimen most closely corresponding to the species description, and bearing both flowers and fruit.

Figures

FIGURE 2. Illustration of M. montrouzieri, with leaf detail of all species. (a) M. montrouzieri habit, leaf and inflorescence, with detail showing idioblasts on leaf undersurface; flower, side view; flower opened out; petals, inner surface (median, 2 upper laterals, 2 lower laterals); ovary and style; fruit with detail of hairs—drawn from Clark, R.P. 160; (a)(i) M. montrouzieri glabrous ovary; (a)(ii) leaf pinna—drawn from Clark, R.P. 150 (specimen formerly identified as M. deverdiana); (b) pinna of M. baudouinii—drawn from Clark, R.P. 141; (c), (c)(i) pinnae of M. schlechteri (showing variation)–drawn from Clark, R.P., 132, 134; (d) pinna of M. rubiginosum—drawn from McPherson, G. 2089; (e) pinna of M. ouenensis—drawn from Balansa, B. 312. Illustration by Margaret Tebbs.

FIGURE 4. Distribution of M. baudouinii