The genera of Leguminosae-Caesalpinioideae & Swartzieae
Type species: B. media Wieringa.
Habit and leaf form. Mostly large trees (with straight cylindrical trunks and fairly low but broad basal buttresses, and creamy to pinkish sapwood); unarmed.
The leaves compound; pinnate; paripinnate. The leaflets many per leaf to few per leaf (1–36 jugate); opposite or sub-opposite (not apically emarginate); sessile to sub-sessile; more or less symmetrical or nearly so, or markedly asymmetrical (basally); pinntely veined, with a predominant midrib; without a continuous marginal nerve (the midrib less displaced than in Aphanocalyx, q.v.). Stipules absent or early caducous or very inconspicuous in mature leaves (caducous); membranous; not connate (the margins valvate, joined only by hairs). Stipels absent.
Inflorescence and floral morphology. The inflorescences axillary (at the terminal nodes, 1–5 per node); branched; of racemose units; panicles (compound racemes, these sometimes more than once branched). Bracts internally glabrous. Bracteoles present; relatively large and enclosing the flower buds; persistent beyond anthesis (extensively fused to the hypanthium).
The flowers hermaphrodite and unisexual (some functionally male, others bisexual); not pentamerous throughout; departing from pentamery in the calyx, in the corolla, and in the androecium. Hypanthium present (small to large). The perianth comprising distinct calyx and corolla, or exclusively petaline. Calyx present, or absent; (0–)2–5; not covering the rest of the flower in bud; much reduced; markedly irregular (the adaxial ones rarely wanting, usually represented by two triangular or semi-circular lobes that are more or less basally fused, the lateral members often wanting, the abaxial one usually present); members not imbricate. Corolla present; very irregular; 1, or 1–5; including greatly reduced members, or without greatly reduced members (the laterals and abaxial strongly reduced or wanting); when detectably polypetalous, polypetalous. Petals clawed (the adaxial one, with a short claw, large and usually only sligtly smaller than the bracteoles, usually widening abruptly above the claw), or sessile; white. The androecium comprising 10 members (usually); with united members (with 9 usually basally united and the laterals often more so, the adaxial one free); members all more or less equal in length to markedly unequal (with the two filaments next to the adaxial one often bending inwards while the laterals bend outwards around it); comprising only fertile stamens. Fertile stamens usually 10. Anthers attached well above the base of the connective; dehiscing purple-red, longitudinally (without dorsal teeth). Ovary present but depauperate in male flowers and with a very short style, in female-fertile flowers stipitate (both stalk and ovary velvety, and the style inserted eccentrically); free. Stigma dilated. Ovules few (1–4).
Fruit, seed and seedling. Fruit a two-valved pod (with a long or short beak); valves twisting and enrolling during dehiscence, or without markedly twisting or enrolling valves; winged longitudinally, or not noticeably winged (winging of the upper suture distict to indistinct); becoming woody, or not becoming woody. The mature valves with conspicuous, prominent, raised venation; conspicuous venation predominantly longitudinal (with the lateral nerve running more or less along the middle of each valve). Seeds not arillate; with a straight or slightly oblique radicle; amyloid-positive. Cotyledons epigeal (the first seedling leaves opposite).
Transverse section of lamina. Leaves with conspicuous phloem transfer cells in the minor veins. Druses common in the mesophyll. Mesophyll secretory cavities absent. Adaxial hypodermis absent. Leaf girders absent. Laminae dorsiventral. Mesophyll without unaligned fibres or sclereids. Minor veins mainly with abundant accompanying fibres.
Leaf lamina epidermes. Epidermal crystals not seen either adaxially or abaxially. Simple unbranched hairs common, or not seen. No compound or branched eglandular hairs seen. Capitate glands not seen. Hooked hairs not seen. Cassieae-type leaf pseudo-glands not seen. Expanded and embedded hair-feet present; all medium to thick-walled; hair feet all simple, without vertical walls. Adaxial: Adaxial interveinal epidermal cell walls markedly sinuous in high-focus optical section; not conspicuously pitted; medium-thin to thin. Stomata adaxially very rare. Abaxial: Abaxial stomata predominantly paracytic. Abaxial epidermis papillate interveinally, or not papillate; with the papillae not over-arching the stomata. Abaxial interveinal epidermal cell walls straight, or gently undulating, or markedly sinuous in high-focus optical section; not conspicuously pitted in optical section; staining normally with safranin; thin.
Wood anatomy. Wood without septate fibres; storied; without normal intercellular canals; without traumatic canals. Intervascular pits medium to large.
Species number and distribution. 10 species. Western tropical Africa.
Tribe. Detarieae (Amherstieae of Cowan and Polhill 1981); Amherstieae clade of Bruneau et al. (2008).
Miscellaneous. Illustrations: • B. letestui and B. pellegrinii: Aubréville, Flore du Gabon (1968), as Monopetalanthus spp.. • B. pellegrinii: Wieringa (1999). • B. aciculifera: Wieringa (1999). • B. breynei: Wieringa (1999). • B. congensis: Wieringa (1999). • B. durandii: Wieringa (1999). • B. durandii (floral morphology): Wieringa (1999).
We advise against extracting comparative information from the descriptions. This is much more easily achieved using the DELTA data files or the interactive key, which allows access to the character list, illustrations, full and partial descriptions, diagnostic descriptions, differences and similarities between taxa, lists of taxa exhibiting or lacking specified attributes, distributions of character states within any set of taxa, geographical distribution, and classification. See also Guidelines for using data taken from Web publications.
Cite this publication as: ‘Watson, L., and Dallwitz, M.J. 1993 onwards. The genera of Leguminosae-Caesalpinioideae and Swartzieae: descriptions, illustrations, identification, and information retrieval. In English and French. Version: 22nd March 2017. delta-intkey.com/caes’.