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The genera of Leguminosae-Caesalpinioideae & Swartzieae

L. Watson and M.J. Dallwitz

Stemonocoleus Harms

Type species: S. micranthus Harms.

Habit and leaf form. Trees; unarmed.

Phyllotaxy spiral. The leaves compound; pinnate; paripinnate. The leaflets relatively few per leaf (8–10); oblong to ovate, apically emarginate, glandular-puncgtate, alternate; petiolulate; with markedly twisted petiolules; markedly asymmetrical; oblique at the base, pinnately veined, with a predominant ‘midrib’. Stipules absent or early caducous or very inconspicuous in mature leaves; membranous. Stipels present, or absent.

Inflorescence and floral morphology. The inflorescences terminal; branched; few flowered, panicles. The flowers not distichous. Bracts naviculate, broadly ovate at the base, with inflexed margins. Bracteoles present; narrowly oblong to lanceolate, dorsally slightly keeled, apically fimbriolate small, not enclosing the flower buds; absent at anthesis; not valvate; free.

The flowers small; hermaphrodite; not pentamerous throughout; departing from pentamery in the calyx, in the corolla, and in the androecium. Floral tube length relative to total hypanthium + calyx length about 0.25. Hypanthium (as the floral structure is usually interpreted) absent, the androecium hypogynous. The perianth exclusively sepaline. Calyx 4; covering the rest of the flower in bud; polysepalous; more or less regular (the sepals slightly unequal); members imbricate. Corolla absent. Disk present and conspicuous (exserted, elongate sheath-like, split unilaterally). The androecium comprising 4 members (inserted on the outer side of the abaxial prolongation of the disk); with united members, or members all free of one another (depending on interpretation of the peculiar ‘disk’); members all more or less equal in length; comprising only fertile stamens. Fertile stamens 4. Anthers attached well above the base of the connective; dehiscing laterally; dehiscing longitudinally. Ovary sessile or subsessile; free. Stigma minutely dilated (capitellate). Ovules few (2).

Fruit, seed and seedling. Fruit 1–2 seeded, flat and thin, indehiscent (basally twisted); winged longitudinally. The mature valves with laxly reticulate venation. Seeds not arillate; with a straight or slightly oblique radicle. Cotyledons not flat; epigeal.

Transverse section of lamina. Druses absent from the mesophyll. Mesophyll secretory cavities (gland-dots) common; epithelium-lined. 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 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; conspicuously pitted; thick. Stomata adaxially very rare. Abaxial: Abaxial epidermis papillate interveinally. Abaxial interveinal epidermal cell walls straight, or gently undulating; conspicuously pitted in optical section; staining normally with safranin; thin.

Wood anatomy. Wood not storied.

Pollen ultrastructure. Tectum striate; interwoven striate. Length of colpi greater than one half pole to pole distance.

Cytology. Basic chromosome number, x = 12.

Species number and distribution. 1 species (S. micranthus). West equatorial Africa.

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

Miscellaneous. Illustrations: • S. micranthus: Nat. Pflanzenfam. (1908).

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.’.