| # The genera of Leguminosae-Caesalpinioideae and Swartzieae |

L. Watson and M.J. Dallwitz

### Parkinsonia L.

Peltophoropsis Chiov., Cercidiopsis Britton & Rose

Type species: P. aculeata L.

Habit and leaf form. Trees, or shrubs; leaves and inflorescences crowded on ‘short shoots’; armed (but without branched spines); usually exhibiting some leaves reduced to phyllodes, and/or with leaflets tiny and early-caducous.

Phyllotaxy spiral. The leaves compound; pinnate and bipinnate (the early leaves pinnate and fasciculate, the later ones bipinnate with short, spine-tipped rachides and flattened pinnae, the pinnae 2–4 pairs, very long and flattened, with numerous very small and sometimes much reduced leaflets); with opposite or sub-opposite leaflets; with rachides adaxially ridged. The leaflets petiolulate. Stipules present, persistent and conspicuous in mature leaves; short, spinescent. Stipels absent.

Inflorescence and floral morphology. The inflorescences axillary; unbranched; lax simple racemes. Bracts small, caducous, absent at anthesis. Bracteoles absent.

The flowers hermaphrodite; pentamerous; coloured. Hypanthium present (but very short), or absent, the androecium hypogynous; when present, saucer-shaped. The perianth comprising distinct calyx and corolla. Calyx 5; covering the rest of the flower in bud; polysepalous; more or less regular, or markedly irregular (with the lowermost sepal somewhat modified, but not housing the fertile parts of the flower); members narrowly imbricate to not imbricate. Corolla present; slightly irregular to very irregular (the petals slightly unequal, with the adaxial one broader); 5; without greatly reduced members; polypetalous. Petals long and short clawed; imbricate; imbricate-ascending; white, or yellow. Disk absent. The androecium comprising 10 members; not declinate; members all free of one another (the filaments basally villous); members all more or less equal in length; comprising only fertile stamens. Fertile stamens 10. Anthers ovoid, attached well above the base of the connective; dehiscing introrsely; dehiscing longitudinally. Ovary stipitate; free. Stigma not dilated (or only minutely so, the style filiform or thick). Ovules few to numerous.

Fruit, seed and seedling. Fruit indehiscent; straight; not internally septate (but often constricted between the seeds); narrowly winged longitudinally, or not noticeably winged; linear, torulose, flattened or turgid, not becoming woody. The mature valves thinly leathery, longitudinally striated. Seeds endospermic; with a straight or slightly oblique radicle; amyloid-negative; with galactomannan. Cotyledons 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 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. 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; of medium thickness. Stomata adaxially common and widespread. Abaxial: Abaxial epidermis not papillate. Abaxial interveinal epidermal cell walls markedly sinuous in high-focus optical section; scarcely staining with safranin; of medium thickness.

Wood anatomy. Wood without septate fibres; not storied. Intervascular pits medium to large.

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.

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

Species number and distribution. About 12 species. Dry regions in North and South America, southern Africa.

Tribe. Caesalpinieae.

Comments. Widely cultivated.

Usually having at least some bipinnate leaves with short, spine-tipped rachides and flattened pinnae.

Miscellaneous. Illustrations: • Parkinsonia aculeata: Fl. Brasiliensis 15 (1870). • Parkinsonia africana: Engler & Drude, Pflanzenwelt Afrikas 9 (1915). • Parkinsonia africana, 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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