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The genera of Leguminosae-Caesalpinioideae & Swartzieae

L. Watson and M.J. Dallwitz

Baikiaea Benth.

Type species: B. insignis Benth.

Habit and leaf form. Trees; unarmed.

Phyllotaxy spiral. The leaves compound; pinnate; imparipinnate, or paripinnate. The leaflets few per leaf; alternate; petiolulate; without noticeably twisted petiolules; symmetrical or nearly so; pinntely veined, with a predominant ‘midrib’; with a strong, continuous marginal nerve. Stipules present, persistent and conspicuous in mature leaves. Stipels absent.

Inflorescence and floral morphology. The inflorescences ‘subterminal’; unbranched; short, crowded simple racemes. The flowers very shortly pedicellate, distichous. Bracts absent at anthesis. Bracteoles present; small, not enclosing the flower buds; absent at anthesis; not valvate; free.

The flowers large; hermaphrodite; not pentamerous throughout; departing from pentamery in the calyx; white or green. Hypanthium absent, the androecium hypogynous (infilled). Calyx 4; not Swartzieae type; polysepalous; members imbricate to not imbricate (subvalvate). Corolla present; slightly irregular; 5 (obovate-spathulate); without greatly reduced members; polypetalous. Petals clawed; imbricate; imbricate-ascending. The androecium comprising 10 members; with united members (with 9 connate basally, and the upper one free); comprising only fertile stamens. Fertile stamens 10 (the alternate filaments basally villous). Anthers attached well above the base of the connective; dehiscing longitudinally. Ovary stipitate; ambiguously free, or eccentric, with the stipe adnate. Stigma dilated. Ovules few, or numerous, or solitary.

Fruit, seed and seedling. Fruit a two-valved pod; valves twisting and enrolling during dehiscence; becoming woody. Seeds arillate; with a straight or slightly oblique radicle; amyloid-positive. Cotyledons of Type 4; with a vascular system in one plane; epigeal.

Transverse section of lamina. Leaves with conspicuous phloem transfer cells in the minor veins. Druses absent from the mesophyll. Mesophyll secretory cavities (gland-dots) common; epithelium-lined. 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; 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 absent. Basally bent hairs present. Adaxial: Adaxial interveinal epidermal cell walls markedly sinuous in high-focus optical section; conspicuously pitted; thin. Stomata adaxially very rare. Abaxial: Abaxial stomata predominantly paracytic. Abaxial epidermis not papillate. Abaxial interveinal epidermal cell walls markedly sinuous in high-focus optical section; conspicuously pitted in optical section; scarcely staining with safranin; of medium thickness.

Wood anatomy. Wood without septate fibres; storied, or not storied; without normal intercellular canals; without traumatic canals. Intervascular pits medium to large.

Pollen ultrastructure. Tectum reticulate; finely to moderately regularly reticulate. Length of colpi greater than one half pole to pole distance. Foot layer of pollen wall smooth.

Cytology. Basic chromosome number, x = 10. 2n = 20.

Species number and distribution. About 8 species (e.g., B. insignis, B. plurijuga, B. zenkeri). Tropical Africa.

Tribe. Detarieae; Detarieae sensu stricto clade of Bruneau et al. (2008).

Comments. Widely cultivated.

Miscellaneous. Illustrations: • B. insignis: Bot. Mag. 145 (1919). • B. insignis, subsp. minor: Brenan, Fl. Tropical East Africa (1967). • B. insignis and B. robynsii: Aubréville, Flore du Gabon (1968). • B. robynsii, 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.’.