The genera of Leguminosae-Caesalpinioideae & Swartzieae
Type species: B. africana Hook.
Habit and leaf form. Trees, or shrubs (with thick branchlets); leaves and inflorescences crowded on short shoots; unarmed.
Phyllotaxy spiral. The leaves compound (silky when young); bipinnate; with opposite or sub-opposite pinnae (few pairs); with alternate leaflets. The leaflets petiolulate; without noticeably twisted petiolules; symmetrical or nearly so; pinntely veined, with a predominant midrib. Stipules absent or early caducous or very inconspicuous in mature leaves; membranous; not connate. Stipels absent.
Inflorescence and floral morphology. The inflorescences unbranched, or branched; when branched, of racemose units; simple racemes (these spicate), or panicles (of interrupted spikes). The flowers not distichous. Bracts absent at anthesis (caducous, small). Bracteoles absent; absent at anthesis.
The flowers small; hermaphrodite; pentamerous; white or green. Hypanthium present to absent, the androecium hypogynous; if present, very short (the androecium scarcely perigynous). Calyx 5; not covering the rest of the flower in bud; gamosepalous; more or less regular; members imbricate. Corolla present; slightly irregular; 5; without greatly reduced members; polypetalous. Petals imbricate; imbricate-ascending; white. The androecium comprising 10 members; members all free of one another (the filaments very short, the connective with an inflexed glandular appendage); members all more or less equal in length, or markedly unequal; comprising only fertile stamens. Fertile stamens 10. Anthers attached at the base of the connective (but sagittate below). Ovary sessile or subsessile, or stipitate; free. Stigma funnel-shaped and split down one side, on the very short style. Ovules few, or solitary.
Fruit, seed and seedling. Fruit indehiscent; without markedly twisting or enrolling valves; not becoming woody. The mature valves with conspicuous, prominent, raised venation, or without prominent venation; conspicuous venation if present, oblique or reticulate, not predominantly longitudinal. Seeds endospermic; with a straight or slightly oblique radicle; amyloid-negative. Cotyledons flat; of Type 2; hypogeal.
Transverse section of lamina. Leaves without conspicuous phloem transfer cells in the minor veins. Druses absent from the mesophyll. Mesophyll secretory cavities absent. Adaxial hypodermis absent. Leaf girders common (the veins transcurrent). 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; scabrid. 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 absent. Basally bent hairs present. Adaxial: Adaxial interveinal epidermal cell walls straight in optical section; not conspicuously pitted; medium-thin. Stomata adaxially very rare. Abaxial: Abaxial stomata predominantly paracytic. Abaxial epidermis not papillate. Abaxial interveinal epidermal cell walls straight, or gently undulating; not conspicuously pitted in optical section; staining normally with safranin; thin.
Wood anatomy. Wood without septate fibres; not storied; without normal intercellular canals; without traumatic canals. Intervascular pits medium to large.
Pollen ultrastructure. Tectum reticulate; rugulose reticulate. Length of colpi greater than one half pole to pole distance (without a margocolpus).
Cytology. Basic chromosome number, x = 14. 2n = 28.
Species number and distribution. 1 species (B. africana), or 2 species (if B. caperangau is accepted). West and southern Africa.
Miscellaneous. Illustrations: • B. africana: Engler & Drude, Pflanzenwelt Afrikas 9 (1915). • B. africana: poor scan from Hook. Ic. Pl. (1842–3).
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’.