The genera of Leguminosae-Caesalpinioideae & Swartzieae
Type species: S. zenkeri Harms.
Habit and leaf form. Trees (with onion-scented bark, at least in S. zenkeri); unarmed.
The leaves compound; pinnate; imparipinnate (or at least with a conspicuous rachis extension). The leaflets many per leaf (about 16–24); alternate; sessile to sub-sessile; markedly asymmetrical; pinnately veined, with a predominant midrib; without a continuous marginal nerve. Stipules absent or early caducous or very inconspicuous in mature leaves (very caducous); membranous; not connate. Stipels absent.
Inflorescence and floral morphology. The inflorescences many flowered, axillary and terminal; unbranched; simple racemes. The flowers not distichous. Bracteoles present; paired, below the middle of the pedicel, linear-lanceolate, very small, not enclosing the flower buds; absent at anthesis; not valvate; free.
The flowers hermaphrodite; not pentamerous throughout; departing from pentamery in the calyx; white or green. Floral tube length relative to total hypanthium + calyx length about 0.5. Hypanthium present; tubular. The perianth comprising distinct calyx and corolla. Calyx 4; covering the rest of the flower in bud; exceeded by the corolla, polysepalous; more or less regular (the sepals ovate); members imbricate. Corolla present; more or less regular; 5; without greatly reduced members; polypetalous. Petals all more or less clawed; similar to one another, obtuse and obovate or oblong-obovate, fimbriate; white. Disk absent. The androecium comprising 10 members; not declinate; members all free of one another (exserted, the filaments filiform and glabrous); comprising only fertile stamens. Fertile stamens 10. Anthers attached well above the base of the connective; dehiscing longitudinally. Ovary hairy, stipitate; eccentric, with the stipe adnate (well down the hypanthium). Stigma small, dilated (capitellate on the slender-elongate, exserted style). Ovules few (two).
Fruit, seed and seedling. Fruit a two-valved pod; valves twisting and enrolling during dehiscence; becoming woody. The mature valves with conspicuous, prominent, raised venation; conspicuous venation not predominantly longitudinal (transverse-reticulately nerved). Seeds non-endospermic; not arillate; with a straight or slightly oblique radicle; amyloid-positive. Cotyledons flat; epigeal.
Transverse section of lamina. Druses common in the mesophyll. Mesophyll secretory cavities absent. 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; 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 markedly sinuous in high-focus optical section; not conspicuously pitted; thin. Stomata adaxially very rare. Abaxial: Abaxial stomata predominantly paracytic. Abaxial epidermis papillate interveinally. Abaxial interveinal epidermal cell walls straight, or gently undulating; not conspicuously pitted in optical section; staining normally with safranin; thin.
Pollen ultrastructure. Tectum striate; interwoven striate. Length of colpi greater than one half pole to pole distance.
Species number and distribution. 2 species (S. fischeri and S. zenkeri). Tropical Africa.
Tribe. Detarieae; Amherstieae clade of Bruneau et al. (2008).
Miscellaneous. Illustrations: • S. zenkeri: Engler, Pflanzenwelt Afrikas (1910).
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’.