| # The genera of Leguminosae-Caesalpinioideae and Swartzieae |

L. Watson and M.J. Dallwitz

### Sclerolobium Vogel

Cf. Amorphocalyx Klotzch and Cosymbe Tul.

Type species: S. denudatum Vogel.

Habit and leaf form. Trees; unarmed.

Phyllotaxy spiral. The leaves compound; pinnate; imparipinnate (rarely, or sometimes the rachis tip extended), or paripinnate (mostly); with adaxially grooved rachides (these often winged). The leaflets opposite or sub-opposite; symmetrical or nearly so; pinnately veined, with a predominant ‘midrib’. Stipules present, persistent and conspicuous in mature leaves, or absent or early caducous or very inconspicuous in mature leaves; variously leafy, or membranous (1–3 foliolate or pinatifid). Stipels absent.

Inflorescence and floral morphology. The inflorescences terminal; branched; of racemose units; panicles (of dense racemes). Bracts minute, or subulate-lanceolate and conspicuous in the bud. Bracteoles present (subulate), or absent; if present, small, not enclosing the flower buds; absent at anthesis; not valvate.

The flowers small; hermaphrodite; actinomorphic to slightly irregular; pentamerous; white or green, or coloured. Hypanthium present; cupular. The perianth comprising distinct calyx and corolla. Calyx 5; covering the rest of the flower in bud; not Swartzieae type; polysepalous; more or less regular (the sepals slightly unequal, the adaxial and abaxial ones similar); members imbricate. Corolla present; regular (the petals only slightly exceeding the sepals, small and slightly unequal); 5; without greatly reduced members; polypetalous. Petals imbricate; imbricate-ascending; white, or yellow. The androecium comprising 10 members; not declinate; members all free of one another (the filaments basally pilose, plicate in the bud); members all more or less equal in length; comprising only fertile stamens. Fertile stamens 10 (the anthers uniform). Anthers attached well above the base of the connective; dehiscing laterally. Ovary stipitate; free. Stigma small, not dilated (terminating the slender, glabrous style). Ovules few to numerous.

Fruit, seed and seedling. Fruit compressed, indehiscent (often with a flaking exocarp); becoming woody, or not becoming woody (with a thinly sub-woody mesocarp and thin, hard, fibrous endocarp). Seeds endospermic, or non-endospermic; not arillate; with a straight or slightly oblique radicle; amyloid-negative.

Transverse section of lamina. Leaves without conspicuous phloem transfer cells in the minor veins. Druses absent from 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 common; scabrid, or smooth. Compound or branched eglandular hairs present, or 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. Adaxial: Adaxial interveinal epidermal cell walls straight in optical section; conspicuously pitted, or not conspicuously pitted; thick to medium-thick. Stomata adaxially very rare. Abaxial: Abaxial stomata predominantly paracytic, or not predominantly paracytic. Abaxial epidermis not papillate. Abaxial interveinal epidermal cell walls straight, or gently undulating; conspicuously pitted in optical section; staining normally with safranin; thick.

Wood anatomy. Wood not storied.

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

Cytology. Basic chromosome number, x = 12, or 13. 2n = 24, or 26.

Species number and distribution. About 40 species. Tropical South America.

Tribe. Caesalpinieae.

Miscellaneous. Illustrations: • Sclerolobium chrysophyllum and S. paniculatum: Fl. Brasiliensis 15 (1870). • Sclerolobium setiferum, 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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