Isolona hexaloba
Tree up to 25-30 m high; d.b.h. to 50 cm, fluted; bark smooth, brown or grey greenish; young branches drying black, glabrous, old branches light grey, glabrous. Petioles 2-4 mm long, 2-3 mm in diameter, glabrous, leaf lamina inserted on side, grooved adaxially. Leaf lamina 10-28 cm long, 3-11 cm long, length:width ratio 2.3-4, narrowly ovate to ovate or narrowly elliptic to elliptic, coriaceous, shiny dark green above, light green below, glabrous, base acute or rarely obtuse, apex acuminate, acumen 1-2 cm long; midrib proximally depressed adaxially, glabrous on both sides; secondary veins 8-16 pairs, uniformally curving upwards, loop forming towards margins, glabrous. Rhipidia 1-2, on leafy branches. Flowering pedicels (7-)13-25(-30) mm long, ca. 0.5 mm in diameter, glabrous, green. Lower bracts 2-4, ca, 0.5 mm long, ca. 0.4 mm wide, glabrous, margins covered with short appressed hairs. Upper bract at the base of the pedicel, 2-5 mm long, 1 mm wide, glabrous, margins covered with short erect hairs. Sepals 1-3 mm long, 2-4 mm wide, length:width ratio 0.5-1, transversely elliptic to elliptic, base truncate, apex shortly acuminate, glabrous, green, pressed against tube, falling in fruit; margins with short erect hairs. Corolla white to yellow or green when immature to dark red at anthesis; tube 4-10 mm long, 4-7 mm in diameter, lobe:tube ratio 1-5, glabrous; lobes 6-25 mm long, 4-12 mm wide, length:width ratio 1.3-2, elliptic or ovate, narrowed at base, apex acute to rounded, glabrous, coriaceous, spreading horizontally. Receptacle 4-6 mm in diameter. Stamens 1.8-2 mm long; connective shield ca. 0.1 mm long, glabrous, those of innermost row elongated over ovary wall. Ovary ca. 1 mm long, ca. 0.5 mm wide; stigma ca. 2 mm in diameter, glabrous, light red at anthesis. Fruiting pedicels 20-25(-29) mm long, 3-5 mm in diameter, woody. Fruits 3-7 cm long, 2.5-4 cm in diameter, broadly ovoid, lumpy, irregularly and transversely ribbed, glabrous, light green to dark purple-red when mature; pericarp 3-4 mm thick. Seeds 8-15 mm long, 4-6 mm in diameter, transversely ellipsoid; testa rugose, light brown; raphe thickened, darker brown; hilum 3-5 mm long, 2-3 mm wide, elliptical.
Isolona hexaloba can be distinguished by the short and grooved petiole with the lamina inserted on the side. The corolla lobes are elliptic to obovate, with a narrowed base and are coriaceous. However, it is a very polymorphic species and has been described under several other names, now all reduced to synonymy. Most of these species names were mainly based on the different lengths of the leaves and flowers. Detailed field notes describe that even after anthesis the corolla lobes continue to grow until flower abscission. The color also changes from light green to yellow and becoming red during anthesis, and dark red just before abscission.
I. hexaloba resembles I. cooperi by the shape of the corolla lobes, but is distinguishable by the insertion of the leaf lamina on a shorter petiole and lacks the strong sweet smell. Isolona hexaloba is also similar to I. pleurocarpa, but the later can be distinguished by the decurrent to narrowly cuneate leaf base, longer petioles, and papyrecous corolla lobes. The molecular phylogeny, however, indicates a moderately supported sister relationship with I. congolana (PP=0.8; BS=53). Finally, I. hexaloba resembles I. lebrunii, but see discussion of that latter species.
The wood is used
for making shields, and when cut finely, for flambeaus (Boutique 1951b). A bark decoction is used against pelvic pains,
constipation or to cure wounds (Neuwinger 2000).
LC. Isolona hexaloba is very well represented in herbaria and is widely distributed in Central Africa, less so in West Africa, and can be found in numerous protected areas. Therefore the “least concern” category is appropriate.
Ghana, Nigeria, Cameroon, southern Central African Republic, Gabon, Congo (Brazzaville), Democratic Republic of Congo and the extreme north-east of Angola; in primary and secondary forests, near rivers, but also found in semi deciduous forests; at 0-700 m altitude.