The genera of Leguminosae-Caesalpinioideae & Swartzieae
Type species: S. afra (L.) Thunb.
Habit and leaf form. Small trees, or shrubs, or herbs, or climbers or scramblers; without tendrils; unarmed.
Phyllotaxy spiral. The leaves compound; pinnate; paripinnate. The leaflets many per leaf, or few per leaf; opposite or sub-opposite; petiolulate, or sessile to sub-sessile; with markedly twisted petiolules, or without noticeably twisted petiolules; markedly asymmetrical to symmetrical or nearly so; pinnately veined, with a predominant midrib; with a strong, continuous marginal nerve, or without a continuous marginal nerve. Stipules short, present, persistent and conspicuous in mature leaves; membranous; connate. Stipels absent.
Inflorescence and floral morphology. The inflorescences unbranched and branched; of racemose units; short simple racemes, or panicles. The flowers not distichous. Bracts ovate or oblong, membranous, very caducous, absent at anthesis. Bracteoles present; small, not enclosing the flower buds; also ovate or oblong, membranous, very caducous, absent at anthesis; not valvate; free.
The flowers showy; hermaphrodite; not pentamerous throughout; departing from pentamery in the calyx; coloured. Floral tube length relative to total hypanthium + calyx length about 0.25–0.5. Hypanthium present; cupular to tubular. The perianth comprising distinct calyx and corolla. Calyx 4; covering the rest of the flower in bud, or not covering the rest of the flower in bud (rarely); polysepalous; more or less regular; members erect and not reflexing, very imbricate. Corolla present; slightly irregular, or very irregular (the petals slightly unequal, or the adaxial, innermost one much reduced); 5; including greatly reduced members, or without greatly reduced members; polypetalous. Petals sessile; imbricate; imbricate-ascending; pink or red. Disk absent. The androecium comprising 10 members; declinate to not declinate; with united members (then shortly connate basally), or members all free of one another; members all more or less equal in length (exceeded by the style); comprising only fertile stamens (the anthers uniform). Fertile stamens 10. Anthers attached well above the base of the connective; dehiscing longitudinally. Ovary stipitate; eccentric, with the stipe adnate. Stigma terminating the elongate style, small, dilated to not dilated. Ovules numerous.
Fruit, seed and seedling. Fruit a two-valved pod, or indehiscent (the valves ultimately separating from the hard, persistent sutural frame); compressed, oblong or broadly linear, straight, or curved (often falcate); without markedly twisting or enrolling valves; winged longitudinally (sometimes margined or winged along the upper suture), or not noticeably winged; becoming woody, or not becoming woody. Seeds non-endospermic; often brightly arillate; with a straight or slightly oblique radicle; amyloid-positive. Cotyledons not flat; 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 common in 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 not seen. No compound or branched eglandular hairs seen. Capitate glands not seen. Expanded and embedded hair-feet absent. Adaxial: Adaxial interveinal epidermal cell walls straight in optical section; not conspicuously pitted; thick. Stomata adaxially very rare. Abaxial: Abaxial stomata not predominantly paracytic (cyclocytic). Abaxial epidermis not papillate. Abaxial interveinal epidermal cell walls straight, or gently undulating; conspicuously pitted in optical section; staining normally with safranin; thick.
Pollen ultrastructure. Tectum striate; reticulate striate, or interwoven striate. Length of colpi greater than one half pole to pole distance. Foot layer of pollen wall with obvious projections.
Cytology. Basic chromosome number, x = 12. 2n = 24.
Species number and distribution. 4–5 species (S. afra, S. brachypetala, S. capitata, S. latifolia). Southern Africa.
Comments. Widely cultivated.
Miscellaneous. Illustrations: • S. tamarindifolia: Bot. Mag. 29–30 (1809). • S. humboldtioides. • S. afra, 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’.