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The genera of Leguminosae-Caesalpinioideae & Swartzieae

L. Watson and M.J. Dallwitz

Dialium L.

Arouna Aubl.; and cf. Andradia Sim, Aruna Schreb., Cleyria Neck, Codarium Sol. ex Vahl

Type species: D. indum L.

Habit and leaf form. Trees; unarmed.

Phyllotaxy spiral. The leaves compound (usually), or ostensibly simple (rarely, e.g. D. procerum); when simple, pinnately veined with a predominant midrib; usually pinnate; imparipinnate. The leaflets of compound leaves, many per leaf, or few per leaf; alternate; petiolulate; without noticeably twisted petiolules; symmetrical or nearly so; pinnately veined, with a predominant ‘midrib’. Stipules absent or early caducous or very inconspicuous in mature leaves; membranous. Stipels absent.

Inflorescence and floral morphology. The inflorescences axillary and terminal; branched; ambiguously of racemose units, or of cymose units; panicles. Bracts absent at anthesis. Bracteoles present; small, not enclosing the flower buds; absent at anthesis, or persistent beyond anthesis (rarely).

The flowers small; hermaphrodite, or hermaphrodite and unisexual (D. guianense being andromonoecious); not pentamerous throughout; departing from pentamery in the calyx, or in the corolla, or in the androecium (exhibiting various combibations); white or green. Hypanthium absent, the androecium hypogynous. The perianth comprising distinct calyx and corolla, or exclusively sepaline. Calyx 3, or 5; covering the rest of the flower in bud; polysepalous; more or less regular; members imbricate. Corolla present (but small), or absent; when present, regular, or slightly irregular, or very irregular; 0–3; including greatly reduced members, or without greatly reduced members; when present, polypetalous, or monopetalous. Petals clawed, or sessile (?); white, or yellow, or red. Disk present and conspicuous, or absent. The androecium comprising 2–6 members; members all free of one another; comprising only fertile stamens. Fertile stamens 2 (commonly), or 3, or 5, or 6. Anthers attached at the base of the connective; dehiscing via pores or short slits, or longitudinally. Ovary sessile or subsessile, or stipitate; free, or eccentric, with the stipe adnate. Stigma dilated, or dilated to not dilated. Ovules few.

Fruit, seed and seedling. Fruit globular, with crustaceous exocarp and pulpy to mealy endocarp, indehiscent; drupaceous. The mature valves without prominent venation. Seeds endospermic; with a straight or slightly oblique radicle; amyloid-negative. Cotyledons flat; of Type 4; with a vascular system in one plane; epigeal.

Transverse section of lamina. Leaves with conspicuous phloem transfer cells in the minor veins. Druses common in the mesophyll (or at least a few near veins), or absent from the mesophyll. Mesophyll secretory cavities absent. Adaxial hypodermis absent. Leaf girders common (the veins transcurrent), or absent. Laminae dorsiventral. Mesophyll without unaligned fibres or sclereids. Minor veins mainly with abundant accompanying fibres.

Leaf lamina epidermes. Epidermal crystals present, or not seen either adaxially or abaxially; prisms, or druses. Simple unbranched hairs common; scabrid. No compound or branched eglandular hairs seen. Capitate glands not seen. Hooked hairs present. Cassieae-type leaf pseudo-glands present. Expanded and embedded hair-feet absent. Basally bent hairs present. Adaxial: Adaxial interveinal epidermal cell walls straight in optical section; conspicuously pitted, or not conspicuously pitted; thick to medium-thick. Stomata adaxially very rare. Abaxial: Abaxial stomata predominantly paracytic. Abaxial epidermis papillate interveinally, or not papillate; with papillae over-arching the stomata. Abaxial interveinal epidermal cell walls markedly sinuous in high-focus optical section; not conspicuously pitted in optical section; staining normally with safranin; medium-thin.

Wood anatomy. Wood storied; without normal intercellular canals; without traumatic canals. Intervascular pits medium to large.

Pollen ultrastructure. Tectum punctate, or striate; rugulose punctate; interwoven striate. Length of colpi greater than one half pole to pole distance.

Cytology. Basic chromosome number, x = 4. 2n = 28.

Species number and distribution. About 40 species. D. guianense in South America, the rest in tropical Africa, Madagascar, Malaysia.

Tribe. Cassieae.

Miscellaneous. Illustrations: • D. guinense (as divaricatum): Fl. Brasiliensis 15 (1870). • D. guianense (= ?) and D. nitidum (= ?): Baillon, Histoire des Plantes 2 (1870). • D. pentandrum: Steyaert, in Fl. du Congo Belge (1952). • D. indum: Fl. Males. 12 (1996). • D. procerum: Fl. Males. 12 (1996). • D. cochinchinense, e.m. scanned pollen (Graham & Barker, 1981). • D. guianense, 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.’.