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The genera of Leguminosae-Caesalpinioideae & Swartzieae

L. Watson and M.J. Dallwitz

Gleditsia L.

Asacara Raf., Caesalpinioides O. Ktze., Garugandra Griseb., Gleditschia Scop., Gleditzia J. St. Hil.

Type species: G. triacanthos L.

Habit and leaf form. Trees (usually), or shrubs (rarely); leaves and inflorescences crowded on ‘short shoots’; armed (with thorns and/or spines, the latter commonly branched).

Phyllotaxy spiral (with supernumerary axillary buds). The leaves compound (the leaflets often serrate); pinnate, or bipinnate, or pinnate and bipinnate (often both, on same specimen); when bipinnnate, with alternate pinnae; with alternate leaflets; when pinnate, paripinnate. The leaflets small to medium sized, many per leaf; opposite or sub-opposite, or alternate; shortly petiolulate, or sessile to sub-sessile; without noticeably twisted petiolules; markedly asymmetrical to symmetrical or nearly so; pinnately veined, with a predominant ‘midrib’ (with the midrib sometimes more or less displaced). Stipules absent or early caducous or very inconspicuous in mature leaves; membranous. Stipels absent.

Inflorescence and floral morphology. The flowers aggregated into inflorescences, or solitary. The inflorescences unbranched, or branched; of racemose units, or of cymose units; simple racemes, or fascicles, or panicles. The flowers not distichous. Bracts small caducous scales, absent at anthesis. Bracteoles absent; absent at anthesis.

The flowers small; hermaphrodite, or unisexual, or hermaphrodite and unisexual (the plants andro- or polygamo-monoecious in G. sinensis and G. triacanthos); pentamerous, or not pentamerous throughout; departing from pentamery in the calyx, or in the corolla, or in the androecium, or in the calyx, in the corolla, and in the androecium (in various combinations); white or green. Floral tube length relative to total hypanthium + calyx length about 0.25–0.5. Hypanthium present; 1–4 mm long, cupular to tubular, or campanulate. The perianth comprising distinct calyx and corolla. Calyx 3–5; not covering the rest of the flower in bud; polysepalous; more or less regular; members sub-imbricate to open in the bud. Corolla present; more or less regular to slightly irregular; 3–5; without greatly reduced members; polypetalous. Petals sessile; imbricate; imbricate-ascending; white. The androecium comprising 6–10 members; members all free of one another; members all more or less equal in length; comprising only fertile stamens. Fertile stamens 6–10. Anthers attached well above the base of the connective; dehiscing laterally; dehiscing longitudinally. Ovary rudimentary or absent in male flowers, in female-fertile flowers sessile or subsessile; free. Stigma dilated (obliquely bilobed on the short style). Ovules few to numerous (2 to many).

Fruit, seed and seedling. Fruit a two-valved pod (dehiscing tardily), or indehiscent; ovate or elongate, compressed, straight to curved (the seeds flattened); leathery or more or somewhat fleshy, not becoming woody. The mature valves without prominent venation. Seeds endospermic; with a straight or slightly oblique radicle; amyloid-negative; with galactomannan. Cotyledons 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 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 absent. Adaxial: Adaxial interveinal epidermal cell walls straight in optical section; not conspicuously pitted; of medium thickness. Stomata adaxially very rare. Abaxial: Abaxial stomata not predominantly paracytic (mixed cyclocytic, actinocytic, anomcytic). Abaxial epidermis not papillate. Abaxial interveinal epidermal cell walls straight, or gently undulating; not conspicuously pitted in optical section; scarcely staining with safranin, or staining normally with safranin; of medium thickness.

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 (no margocolpus). Foot layer of pollen wall with obvious projections.

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

Species number and distribution. About 15 species. Tropical and subtropical.

Tribe. Caesalpinieae.

Comments. Widely cultivated.

Miscellaneous. Illustrations: • G. triacanthos: Nat. Pflanzenfam. III (1894). • G. fera and G. australis: li shu gang (2005).

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.’.