Isolona ghesquierei
Tree up to 15 m high; d.b.h. to 15 cm; young branches drying black, smooth, glabrous; old branches dark grey, striate, glabrous. Petioles 6-9 mm long, 1 mm in diameter, glabrous, leaf lamina inserted on side, weakly grooved adaxially. Leaf lamina (6-)9.5-16 cm long, (2-)3-6.5 cm wide, length:width ratio 2-3, elliptic to obovate, rounded, glabrous, base acute to broadly cuneate, apex acuminate, acumen 5-15 mm long; midrib glabrous on both sides; secondary veins 7-11 pairs, uniformly curving upwards, glabrous. Rhipidium 1, on leafy branches. Flowering pedicels 4-10(-16) mm long, 1-1.5 mm in diameter, very sparsely covered with short appressed hairs. Lower bracts 2-3, ca. 0.5 mm long, ca. 0.5 mm wide, glabrous, margins sparsely covered with short appressed hairs. Upper bract absent. Sepals ca. 2 mm long, ca. 3 mm wide, length:width ratio ca. 0.6, depressed ovate, base truncate, apex cuspidate, glabrous, pressed against tube, falling in fruit; margins sparsely covered with short appressed hairs. Corolla dark red at anthesis; tube 6-11 mm long, 4-6 mm in diameter, lobe:tube ratio 4-8, glabrous; lobes 15-45 mm long, 5-11 mm wide, length:width ratio 2.5-4, narrowly elliptic to elliptic, narrowed at base, apex acute with rounded tip, glabrous, membraneous when dried, wavy and pointing downwards, margins sparsely covered with short erect hairs. Receptacle ca. 4 mm in diameter. Stamens ca. 1.5 mm long; connective shield ca. 0.1 mm long, glabrous, those of innermost stamens extended over adjacent ovary wall. Ovary ca. 2 mm long ca. 1.5 mm wide; stigma ca. 2 mm in diameter, glabrous to very sparsely covered with short appressed hairs. Fruiting pedicels ca. 10 mm long, 4-5 mm in diameter, woody, glabrous. Fruits 4-7 cm long, 4-5 cm in diameter, length:width ratio 1-1.5, globose to ovoid, smooth, glabrous, green; pericarp ca. 4 mm thick. Seeds 15-19 mm long, 8-10 mm in diameter, ellipsoid; testa smooth, light brown; raphe not thickened, darker brown; hilum 4-6 mm long, 3-4 mm wide, elliptical.
Isolona ghesquierei can be recognized by its often large and conspicuous papery corolla lobes, and generally short flowering pedicels sparsely covered with hairs. All other Isolona species in Madagascar have glabrous flowering pedicels.
The variety longipedicellata, recognized because of a longer pedicel, is no longer maintained as pedicel length seems to be quite variable and a more or less continuous variation was observed.
EN B2ab(iii). Isolona ghesquierei is not well represented in herbaria, but has been collected recently (2003 and 2005). Moreover, it occurs in one national park (Marojejy). However, its AOO is less than 200 km2 thus the “endangered” category seems applicable.
Eastern Madagascar; in primary and secondary rain forests; at 0-1100 m altitude.