Tetrapleura Benth., J. Bot. (Hooker) 4: 345. 1841.

Figs 104, 105, 106, 108

Type.

Tetrapleura thonningii Benth., nom. illeg. [= Tetrapleura tetraptera (Schumach. & Thonn.) Taub. (≡ Adenanthera tetraptera Schumach. & Thonn.)]

Description.

Unarmed trees or shrubs 8-25 m tall (Fig. 104D), to 60-90 cm in diameter, usually lacking buttresses but occasionally with short, sharp buttresses; bark smooth, dark brown, very thin, slightly spongy; brachyblasts absent. Stipules not observed. Leaves bipinnate, 10-40 cm long, foliar glands absent; pinnae 2-10 (15) pairs per leaf, opposite to subopposite; leaflets alternate, 6-26 per pinna, petiolulate. Inflorescences of solitary or paired spiciform axillary racemes, 5-10 cm long (Fig. 105C), usually borne on older wood and immersed in the foliage, but the leaves sometimes suppressed and the racemes forming a pseudopanicle. Flowers hermaphrodite, pedicellate, the pedicel abscising with the flowers, small persistent triangular bracts at the base of each flower; calyx conical, shallow, 5-toothed, valvate in bud; petals 5, free, linear-lanceolate, cream to pale pink aging orange-red, valvate in bud (Fig. 105B,C); stamens 10, free, slightly exserted above the petals, filaments white, anthers with a caducous apical gland; pollen in 16-grained calymmate polyads; ovary oblong, sessile, glabrous, stigma porate. Fruits straight, oblong, woody, indehiscent, 10-20 cm long, four-winged with flattened sutural ribs and longitudinal wings running down the centre of the valve (Fig. 106E), each wing to 1 cm broad, two of the wings filled with pulp, cruciform in cross-section, dark brown, pods internally septate between the seeds with spongy, fibrous endocarp. Seeds inserted transversely, brown, smooth, unwinged, testa hard, pleurogram present.

Chromosome number.

2 n = 26 (Fedorov 1969).

Included species and geographic distribution.

Two species in tropical Africa, in the Guineo-Congolese forest from Senegal to Sudan, Uganda, and Kenya, south to Angola and Tanzania (Fig. 108).

Ecology.

Common in secondary forest but growing best in undisturbed rainforest; high forest zones, riverine forests, southern savanna woodland, and as forest outliers in the African plains.

Etymology.

From the Greek, tetra (= four) and pleura (= ribs), referring to the four ribs on the fruits.

Human uses.

A valued forest species for its fragrant fruits and seeds which are used to season food. The fruits, seeds, leaves, and bark are all used in folk medicine to treat a wide variety of ailments. The chemistry of the fruits has been studied and found to be a potential treatment for diabetes and to reduce inflammation (Orwa et al. 2009; Kuate et al. 2015).

Notes.

Tetrapleura differs from Amblygonocarpus in Hoffmannseggia minor characters as described below under Amblygonocarpus . Although they might be treated as a single genus, the two genera tend to be ecologically distinct. Tetrapleura is a rainforest tree that only occasionally moves into the savanna as a forest outlier whereas Amblygonocarpus is a true inhabitant of savannas and deciduous forests.

Taxonomic references.

Brenan (1959) with illustration; Kemigisha et al. (2018).