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The genera of Leguminosae-Caesalpinioideae & Swartzieae

L. Watson and M.J. Dallwitz

Delonix Rafin.

Poinciana regia Hook.

Type species: D. regia (Boj.) Raf.

Habit and leaf form. Deciduous trees; unarmed.

Phyllotaxy spiral. The leaves compound; bipinnate; with opposite or sub-opposite pinnae; with opposite or sub-opposite leaflets; with adaxially grooved rachides. The leaflets small, many per leaf; petiolulate, or sessile to sub-sessile; markedly asymmetrical to symmetrical or nearly so; with a predominant ‘midrib’. Stipules absent or early caducous or very inconspicuous in mature leaves; membranous. Stipels absent.

Inflorescence and floral morphology. The inflorescences terminal; unbranched, or branched; usually comprising racemes combined into lax or dense corymbs. The flowers not distichous. Bracts small, absent at anthesis (caducous). Bracteoles absent; absent at anthesis.

The flowers large and showy; hermaphrodite; pentamerous; coloured. Floral tube length relative to total hypanthium + calyx length when applicable, about 0.25. Hypanthium present, or absent, the androecium hypogynous; when present. cupular. Calyx 5; covering the rest of the flower in bud; polysepalous; more or less regular; members not imbricate. Corolla present; slightly irregular, or very irregular; 5; without greatly reduced members (with Aprevalia excluded); polypetalous. Petals clawed (orbicular above the claws); imbricate; imbricate-ascending; white, or yellow, or red. The androecium comprising 10 members; members all free of one another; members members alternately slightly longer and shorter; comprising only fertile stamens. Fertile stamens 10. Anthers attached well above the base of the connective (dorsifixed); dehiscing introrsely; dehiscing longitudinally. Ovary sessile or subsessile; free. Stigma dilated, or not dilated. Ovules numerous.

Fruit, seed and seedling. Fruit a two-valved pod; curved; without markedly twisting or enrolling valves; not noticeably winged; becoming woody, or not becoming woody (leathery in African species). The mature valves with conspicuous, prominent, raised venation; conspicuous venation predominantly longitudinal. Seeds endospermic; with a straight or slightly oblique radicle; amyloid-negative; with galactomannan. Cotyledons flat; of Type 3; with a vascular system in one plane; epigeal.

Transverse section of lamina. Leaves without conspicuous phloem transfer cells in the minor veins. 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 lacking accompanying fibrous tissue.

Leaf lamina epidermes. Epidermal crystals not seen either adaxially or abaxially. Simple unbranched hairs common; scabrid, or 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. Adaxial: Adaxial interveinal epidermal cell walls straight in optical section; conspicuously pitted, or not conspicuously pitted; thin. Stomata adaxially common and widespread, or 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; scarcely staining with safranin; thin.

Wood anatomy. Wood with septate fibres; storied, or not storied. Intervascular pits very small.

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

Cytology. Basic chromosome number, x = 14. 2n = 28.

Species number and distribution. 9–11 species. Tropical Africa, Madagascar, Asia.

Tribe. Caesalpinieae.

Comments. Widely cultivated.

Miscellaneous. Illustrations: • D. regia: Bot. Mag. 50 (1829). • D. elata (as Poinciana): Engler & Drude, Pflanzenwelt Afrikas 9 (1915). • D. regia: Fl. Males. 12 (1996). • D. elata, 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.’.