The genera of Leguminosae-Caesalpinioideae & Swartzieae
Type species: B. acuminata Soland. ex Hook. f.
Habit and leaf form. Trees, or shrubs (rarely); unarmed.
Phyllotaxy spiral. The leaves compound; pinnate; paripinnate. The leaflets few per leaf; opposite or sub-opposite; petiolulate; without noticeably twisted petiolules; basally markedly asymmetrical, or symmetrical or nearly so; pinnately veined, with a predominant midrib; without a continuous marginal nerve. Stipules absent or early caducous or very inconspicuous in mature leaves, or present, persistent and conspicuous in mature leaves; leafy, or membranous. Stipels absent.
Inflorescence and floral morphology. The inflorescences terminal (on the branchlets); unbranched, or branched; when branched, of racemose units; simple corymbs, or panicles. The flowers not distichous. Bracts absent at anthesis (caducous, leathery). Bracteoles present (spathulate); relatively large and enclosing the flower buds; absent at anthesis; valvate.
The flowers medium-sized; hermaphrodite; pentamerous, or not pentamerous throughout; departing from pentamery in the corolla, or in the androecium, or in the corolla and in the androecium; white or green. Floral tube length relative to total hypanthium + calyx length about 0.5. Hypanthium present; cupular to tubular. Calyx 5; not Swartzieae type; polysepalous; members imbricate. Corolla present; very irregular (the upper petal larger, hooded and folded in bud, the 2–4 lower ones small and linear or absent); 1–5; including greatly reduced members, or without greatly reduced members; polypetalous. Petals clawed (the large one), or sessile; white. Disk absent. The androecium comprising 10 members; with united members (9 basally united, 1 free); members markedly unequal; comprising only fertile stamens. Fertile stamens 10. Anthers attached well above the base of the connective. Ovary stipitate; eccentric, with the stipe adnate. Stigma dilated (on the filiform style, at least in B. baumii). Ovules numerous.
Fruit, seed and seedling. Fruit a two-valved pod; curved; valves twisting and enrolling during dehiscence; becoming woody. The mature valves with conspicuous, prominent, raised venation; conspicuous venation not predominantly longitudinal. Seeds with a straight or slightly oblique radicle; amyloid-positive. Cotyledons epigeal.
Transverse section of lamina. Leaves with 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), or 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; scabrid, or smooth. 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, or absent; all medium to thick-walled; hair feet (at least some of them) complex with vertical walls. Basally bent hairs present. Adaxial: Adaxial interveinal epidermal cell walls markedly sinuous in high-focus optical section; not conspicuously pitted; thin. Stomata adaxially very rare. Abaxial: Abaxial stomata predominantly paracytic. Abaxial epidermis papillate interveinally, or not papillate; with papillae over-arching the stomata. Abaxial interveinal epidermal cell walls markedly sinuous in high-focus optical section; not conspicuously pitted in optical section; staining normally with safranin; medium-thin to thin.
Wood anatomy. Wood without septate fibres; not storied; without normal intercellular canals; with traumatic canals. Intervascular pits medium to large.
Pollen ultrastructure. Tectum punctate, or striate; smooth punctate, or puncticulate; pole to pole striate. Length of colpi greater than one half pole to pole distance.
Cytology. Basic chromosome number, x = 12. 2n = 24.
Species number and distribution. 16 species. Tropical Africa.
Tribe. Detarieae (Amherstieae of Cowan and Polhill 1981); Amherstieae clade of Bruneau et al. (2008).
Miscellaneous. Illustrations: • B. grandiflora (as heudelotiana) and B. acuminata (= ?), with ‘Vouapa’ spp.: Baillon, Adansonia VI (1865). • B. grandiflora: Leonard, Fl. du Congo Belge (1952). • B. auriculata and B. confusa: Aubréville, Flore du Gabon (1968). • B. (Pseudoberlinia) baumii: Baum (1903). • B. tomentella: leaflet, abaxial epidermis with embedded hair-feet. • B. giorgii and B. grandiflora, e.m. scanned pollen (Graham & Barker, 1981).
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’.