Hexalobus A. DC., Mém. Soc. Phys. Genève 5: 212, 1832

Type species.

Hexalobus monopetalus (A. Rich.) Engl. & Diels.

Description.

Trees, 10-40 m tall, d.b.h. 35-100 cm; stilt roots or buttresses absent, but trunk strongly fluted. Indumentum of simple hairs. Leaves: petiole 1-8 mm long, 1-4 mm in diameter; blade 3.6-36 cm long, 1.2-10 cm wide, elliptic or obovate or ovate, apex acuminate or rounded to obtuse, base cuneate or cordate, concolorous; midrib sunken or flat; secondary veins 5 to 17 pairs; tertiary venation reticulate. Individuals bisexual; inflorescences ramiflorous on old leafless or young foliate branches, axillary. Flowers with 9 perianth parts in 2 whorls, 1 to 3 per inflorescence; pedicel (0)1-15 mm long, 1-5 mm in diameter; in fruit 2-30 mm long, 1-5 mm in diameter; bracts 5 to 6, several basal and two (sometimes fused) on upper half of pedicel; sepals 3, valvate, free, 4-21 mm long, 3-14 mm wide, ovate, apex acute, base truncate; petals 6, in a single whorl and basally fused, tube 2-10 mm long, inner and outer whorl not differentiated, equal or subequal; lobes 9-80 mm long, 3-21 mm wide, margins plicate (folded in bud) or wavy; stamens numerous, in 10 to 13 rows, 1-8 mm long, elongated; connective discoid or elongated; staminodes absent; carpels free, 2 to 16, ovary 2-5 mm long, stigma bilobed or divided into two lobes with margins coiled inwards. Fruit apocarpous, monocarps stipitate or sessile, stipes 0-3 mm long; monocarps 1 to 8, 22-95 mm long, 13-65 mm in diameter, ellipsoid to cylindrical, apex rounded, smooth or rugose or warty, pubescent, orange-brown to medium brown when ripe; seeds 2 to 36, 10-40 mm long, 7-20 mm in diameter, flattened ellipsoid; aril absent.

A genus of five species, distributed across Africa. Four species are known from Cameroon, one endemic.

This genus of trees is characterized by thin plicate (folded) petals, a unique character for Annonaceae (Botermans et al. 2011). In addition, the petals are fused at the base and form a short tube with 6 lobes, a character otherwise only seen in Isolona. The trunk of adult trees is strongly fluted, a character also seen in the larger species of the genus Isolona (e.g. I. hexaloba).

Taxonomy.

Botermans et al. (2011).