| # The genera of Leguminosae-Caesalpinioideae and Swartzieae |

L. Watson and M.J. Dallwitz

### Cercidium Tul.

~ Parkinsonia.

Type species: C. praecox (R. & P.) Harms.

Habit and leaf form. Trees, or shrubs (the branches often twisted); leaves and inflorescences crowded on ‘short shoots’; armed (with short straight spines at the nodes).

Phyllotaxy spiral. The leaves small, but compound; bipinnate (with 1–2 pairs of pinnae, each with few pairs of small leaflets); with opposite or sub-opposite pinnae; with opposite or sub-opposite leaflets; with rachides adaxially ridged. The leaflets many per leaf; petiolulate; without noticeably twisted petiolules; 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 lateral at the often leafless nodes; short, lax simple racemes. The flowers not distichous. Bracts small. Bracteoles absent; absent at anthesis.

The flowers hermaphrodite; pentamerous; coloured. Floral tube length relative to total hypanthium + calyx length about 0.25. Hypanthium present; hortly campanulate. The perianth comprising distinct calyx and corolla. Calyx 5; covering the rest of the flower in bud; more or less regular (or only slightly irregular); members not imbricate (valvate). Corolla present; slightly irregular to very irregular (the adaxial member differing somewhat from the others); 5; without greatly reduced members; polypetalous. Petals clawed and sessile; oblong or orbicular, imbricate; imbricate-ascending; yellow. Disk present and conspicuous. The androecium comprising 10 members; members all free of one another; comprising only fertile stamens. Fertile stamens 10. Anthers attached well above the base of the connective; dehiscing introrsely. Ovary stipitate; free. Stigma not dilated. Ovules numerous.

Fruit, seed and seedling. Fruit indehiscent; straight; not internally septate; without markedly twisting or enrolling valves; not becoming woody. The mature valves with conspicuous, prominent, raised venation; conspicuous venation not predominantly longitudinal (but obliquely so). Seeds endospermic; with a straight or slightly oblique radicle; amyloid-negative; with galactomannan. Cotyledons not flat; of Type 2; 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 isobilateral, with adaxial and abaxial palisades, or 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; 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 absent. Adaxial: Adaxial interveinal epidermal cell walls straight in optical section; conspicuously pitted; medium-thin. Stomata adaxially common and widespread. Abaxial: Abaxial stomata not predominantly paracytic (anomcytic, actinocytic and cyclocytic). Abaxial epidermis not papillate. Abaxial interveinal epidermal cell walls straight, or gently undulating, or markedly sinuous in high-focus optical section; conspicuously pitted in optical section; scarcely staining with safranin, or staining normally with safranin; medium-thin.

Wood anatomy. Wood without septate fibres; not storied. Intervascular pits very small.

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

Species number and distribution. 5–10 species. Warm America.

Tribe. Caesalpinieae.

Comments. Widely cultivated.

Miscellaneous. Illustrations: • Cercidium praecox: http://www.mergili.at/worldimages/picture.php?/2470. • Cercidium floridum subsp. peninsulare, 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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