| # The genera of Leguminosae-Caesalpinioideae and Swartzieae |

L. Watson and M.J. Dallwitz

### Bussea Harms

Type species: B. massaiensis (Taub.) Harms.

Habit and leaf form. Trees, or shrubs; unarmed.

Phyllotaxy spiral. The leaves compound; bipinnate; with opposite or sub-opposite leaflets, or with alternate leaflets; with adaxially grooved rachides. The leaflets petiolulate, or sessile to sub-sessile; 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. Stipels absent.

Inflorescence and floral morphology. The inflorescences branched; of racemose units; panicles (of racemes). The flowers not distichous. Bracts absent at anthesis. Bracteoles absent; absent at anthesis.

The flowers hermaphrodite; pentamerous. Floral tube length relative to total hypanthium + calyx length about 0.25. Hypanthium present; cupular. Calyx 5 (the sepals with hyaline margins); covering the rest of the flower in bud; polysepalous; more or less regular, or markedly irregular; members imbricate. Corolla present; slightly irregular, or very irregular; 5; without greatly reduced members; polypetalous. Petals clawed (spathulate and corrugated); imbricate; yellow. The androecium comprising 10 members; members all free of one another; comprising only fertile stamens. Fertile stamens 10. Anthers dehiscing introrsely. Ovary sessile or subsessile; free. Stigma dilated (the style pilose). Ovules few.

Fruit, seed and seedling. Fruit a two-valved pod; without markedly twisting or enrolling valves (these revolute); becoming woody. Seeds non-endospermic; with a straight or slightly oblique radicle; amyloid-negative; with starch.

Transverse section of lamina. Leaves without conspicuous phloem transfer cells in the minor veins. Druses common in the mesophyll. Mesophyll secretory cavities (gland-dots) common; epithelium-lined, or without a lining of epithelium. 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; 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, or absent. Adaxial: Adaxial interveinal epidermal cell walls straight in optical section, or markedly sinuous in high-focus optical section; conspicuously pitted. Stomata adaxially very rare. Abaxial: Abaxial stomata predominantly paracytic. Abaxial epidermis not papillate. Abaxial interveinal epidermal cell walls straight, or gently undulating, or markedly sinuous in high-focus optical section; conspicuously pitted in optical section; staining normally with safranin; of medium thickness to medium-thin.

Wood anatomy. Wood with septate fibres; not storied.

Pollen ultrastructure. Tectum reticulate; finely to moderately regularly reticulate. Length of colpi greater than one half pole to pole distance (without a margocolpus). Foot layer of pollen wall with obvious projections.

Cytology. Basic chromosome number, x = 11. 2n = 22.

Species number and distribution. 6–7 species. Madagascar and tropical Africa.

Tribe. Caesalpinieae.

Miscellaneous. Illustrations: • Bussea massaiensis: Nat. Pflanzenfam., 1908. • Bussea gossweileri: Wilczek, in Fl. du Congo Belge (1952). • Bussea occidentalis, 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: 4th August 2019. delta-intkey.com’.

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