The Genera of Leguminosae-Caesalpinioideae and Swartzieae

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L. Watson and M. J. Dallwitz

Melanoxylon Schott

Habit and leaf form. Trees; without tendrils; unarmed. Phyllotaxy spiral. Leaves compound; pinnate; imparipinnate; with adaxially grooved rachides. Leaflets many per leaf; opposite or sub-opposite; petiolulate; with petiolules not noticeably twisted. Stipels absent.

Inflorescence and floral morphology. Flowers hermaphrodite; pentamerous; in panicles (large, of racemes); not distichous. Inflorescences terminal; of racemose units. Bracts absent at anthesis. Bracteoles present; absent at anthesis. Hypanthium present (oblique-campanulate). Calyx polysepalous; covering the rest of the flower in bud; more or less regular (lowermost sepal not modified); 5 partite; imbricate. Corolla present; slightly zygomorphic; polypetalous; without any greatly reduced petals. Petals 5; imbricate; imbricate-ascending. Androecium of ten parts; members all free of one another; members all more or less equal in length; without staminodia. Fertile stamens 10. Anthers attached well above base of connective (hairy). Dehiscence introrse; longitudinal. Ovary sessile or subsessile; free. Stigma not peltate (small). Ovules numerous.

Fruit, seed and seedling. Fruit a two-valved pod; becoming distinctly woody (somewhat); curved; internally septate; not winged; without markedly twisting or enrolling valves. Seeds endospermic (with a falcate wing at the apex); with a straight or slightly oblique radicle; amyloid-negative.

Transverse section of lamina. Leaves without conspicuous phloem transfer cells in the minor veins. Druses absent from the mesophyll. Mesophyll secretory cavities absent. Adaxial hypodermis absent. Leaf girders absent. 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. Adaxial interveinal epidermal cell walls straight in optical section; not conspicuously pitted; medium-thick. Stomata adaxially very rare. Abaxial stomata predominantly paracytic. Abaxial epidermis not papillate. Abaxial interveinal epidermal cell walls straight, or gently undulating, or markedly sinuous in high-focus optical section; not conspicuously pitted in optical section; scarcely staining with safranin, or staining normally with safranin; thin.

Wood anatomy. Wood storied.

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 smooth.

Cytology, geography, etc. 3 species. Tropical South America. Not widely cultivated.

Tribe. Caesalpinieae.


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Cite this publication as: ‘Watson, L., and Dallwitz, M.J. 1993 onwards. The genera of Leguminosae-Caesalpinioideae and Swartzieae: descriptions, identification, and information retrieval. In English and French; French translation by E. Chenin. Version: 22nd March 2009. http://delta-intkey.com’.

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