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The genera of Leguminosae-Caesalpinioideae & Swartzieae

L. Watson and M.J. Dallwitz

Hardwickia Roxb.

Type species: H. binata Roxb.

Habit and leaf form. Trees; unarmed.

Phyllotaxy spiral. The leaves compound; bifoliolate; paripinnate. The leaflets leathery, few per leaf (two only); opposite or sub-opposite; markedly asymmetrical; palmately nerved. Stipules absent or early caducous or very inconspicuous in mature leaves; membranous. Stipels absent.

Inflorescence and floral morphology. The inflorescences axillary and terminal; branched; of racemose units; panicles (of racemes). The flowers not distichous. Bracts caducous, minute, absent at anthesis. Bracteoles present (under the calyx); scale-like, small, not enclosing the flower buds; absent at anthesis; not valvate; free.

The flowers small; hermaphrodite; not pentamerous throughout; departing from pentamery in the corolla. Hypanthium absent, the androecium hypogynous. The perianth exclusively sepaline (but petaloid). Calyx petaloid, 5 (the sepals orbicular); covering the rest of the flower in bud; polysepalous; more or less regular (the orbicular sepals subequal); members very imbricate. Corolla absent. Disk present and conspicuous. The androecium comprising 10 members; members all free of one another; members markedly unequal (alternately longer and shorter); comprising only fertile stamens. Fertile stamens 10. Anthers attached well above the base of the connective; dehiscing laterally; dehiscing longitudinally. Ovary sessile or subsessile; free. Stigma dilated (large and peltate on the filiform style). Ovules few (2).

Fruit, seed and seedling. Fruit indehiscent (lanceolate, compressed, the single seed distal); not drupaceous; not becoming woody. The mature valves with conspicuous, prominent, raised venation; conspicuous venation predominantly longitudinal. Seeds non-endospermic; with a straight or slightly oblique radicle; amyloid-negative.

Transverse section of lamina. Leaves with conspicuous phloem transfer cells in the minor veins. Druses absent from the mesophyll. Mesophyll secretory cavities absent. 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 not seen. No compound or branched eglandular hairs seen. Capitate glands not seen. Expanded and embedded hair-feet absent. Adaxial: Stomata adaxially common and widespread. Abaxial: Abaxial stomata predominantly paracytic. Abaxial epidermis papillate interveinally; with the papillae not over-arching the stomata. Abaxial interveinal epidermal cell walls straight, or gently undulating; conspicuously pitted in optical section; staining normally with safranin; of medium thickness.

Wood anatomy. Wood without normal intercellular canals; with traumatic canals. Intervascular pits very small.

Pollen ultrastructure. Tectum papillate; reticulate papillate. Length of colpi inapplicable — grain periporate.

Cytology. Basic chromosome number, x = 17. 2n = 68.

Species number and distribution. 2 species (H. binata and H. mannii). India.

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

Miscellaneous. Illustrations: • H. binata: D. Brandis, Indian trees (1906). • H. binata, 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.’.