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The genera of Leguminosae-Caesalpinioideae & Swartzieae

L. Watson and M.J. Dallwitz

Hymenaea L.

Type species: H. courbaril L.

Habit and leaf form. Trees (with pellucid-punctate leaflets and floral parts); very leaves and inflorescences crowded on ‘short shoots’; unarmed.

Phyllotaxy distichous, or spiral. The leaves compound; bifoliolate; paripinnate. The leaflets few per leaf (only two); petiolulate, or sessile to sub-sessile; with markedly twisted petiolules; markedly asymmetrical (very much so at the base); pinnately nerved from the laterally displaced midrib, with a predominant ‘midrib’; without a continuous marginal nerve. Stipules absent or early caducous or very inconspicuous in mature leaves (broadly linear,); membranous. Stipels absent.

Inflorescence and floral morphology. The inflorescences terminal; branched; of racemose units; densely corymbose panicles. The flowers not distichous. Bracts small, caducous, absent at anthesis. Bracteoles present; small, not enclosing the flower buds, or relatively large and enclosing the flower buds; persistent beyond anthesis, or absent at anthesis; not valvate; free.

The flowers hermaphrodite; not pentamerous throughout; departing from pentamery in the calyx; white or green. Floral tube length relative to total hypanthium + calyx length about 0.25. Hypanthium present; very thick, shortly cupular, or campanulate. The perianth comprising distinct calyx and corolla. Calyx 4; covering the rest of the flower in bud; not Swartzieae type; polysepalous (leathery, pellucid-glandular); more or less regular. Corolla present; slightly irregular (usually, when all five petals are subequal), or very irregular; 5 (usually glandular-pustulate); including greatly reduced members (occasionally with two reduced), or without greatly reduced members (usually); polypetalous. Petals sessile; imbricate; imbricate-ascending; pellucid-glandular, white. Disk present and conspicuous (filling the hypanthium). The androecium comprising 10 members; members all free of one another; members all more or less equal in length; comprising only fertile stamens. Fertile stamens 10. Anthers attached well above the base of the connective; dehiscing longitudinally. Ovary stipitate; eccentric, with the stipe adnate. Stigma dilated. Ovules few to numerous (2–18).

Fruit, seed and seedling. Fruit resin dotted, indehiscent; not drupaceous; becoming woody. Seeds non-endospermic; not arillate; with a straight or slightly oblique radicle; amyloid-positive. Cotyledons of Type 4; with a vascular system ramified throughout.

Transverse section of lamina. Leaves with conspicuous phloem transfer cells in the minor veins. Druses absent from the mesophyll. Mesophyll secretory cavities (gland-dots) common; epithelium-lined. 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; 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 markedly sinuous in high-focus optical section; not conspicuously pitted; thin. Stomata adaxially very rare. Abaxial: Abaxial stomata predominantly paracytic. Abaxial epidermis not papillate. Abaxial interveinal epidermal cell walls markedly sinuous in high-focus optical section; conspicuously pitted in optical section; staining normally with safranin; medium-thick.

Wood anatomy. Wood without septate fibres; not storied; without normal intercellular canals; with traumatic canals. Intervascular pits medium to large.

Pollen ultrastructure. Tectum reticulate; rugulose reticulate. Length of colpi greater than one half pole to pole distance.

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

Species number and distribution. About 15 species (excluding Trachylobium, = Hymenaea verrucosa). Mexico, Cuba, tropical South America.

Tribe. Detarieae; Detarieae sensu stricto clade of Bruneau et al. (2008).

Comments. Widely cultivated.

Miscellaneous. Illustrations: • H. stigonocarpa: Fl. Brasiliensis 15 (1870). • H. coubaril: Schery, Ann. Miss. Bot. Gard. 38 (1951). • H. courbaril, H. verrucosa (as Trachylobium hornemannianum), with Detarium senegalense (cf. D. microcarpum): Nat. Pflanzenfam. III (1894). • H. martiana, 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.’.