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The genera of Leguminosae-Caesalpinioideae & Swartzieae

L. Watson and M.J. Dallwitz

Bauhinia L. (sensu stricto)

Alvesia Welw. (= B. acuminata), Caspariopsis (= B. monandra)

Type species: B. divaricata L.

Habit and leaf form. Trees, or shrubs (without tendrils).

Phyllotaxy distichous, or spiral. The leaves two-lobed; when simple or bilobed palmately veined. Stipules absent or early caducous or very inconspicuous in mature leaves, or present, persistent and conspicuous in mature leaves; when present, membranous; not connate. Stipels absent.

Inflorescence and floral morphology. The inflorescences axillary (rarely), or terminal; unbranched, or branched; when branched, of racemose units; simple racemes, or simple corymbs, or panicles. The flowers not distichous. Bracts absent at anthesis. Bracteoles present; small, not enclosing the flower buds; absent at anthesis, or persistent beyond anthesis.

The flowers all hermaphrodite (usually), or hermaphrodite and unisexual (e.g., polygamo-dioecious in B. macranthera, andromonoecious in B. divaricata); pentamerous (rarely), or not pentamerous throughout; coloured. Floral tube length relative to total hypanthium + calyx length about 0.2–1. Hypanthium present; long tubular (to funnel-shaped). Calyx covering the rest of the flower in bud; gamosepalous; markedly irregular (spathaceous, splitting down one side but otherwise remaining entire for almost its whole length); members not imbricate. Corolla present; slightly irregular; (2–)5; without greatly reduced members; polypetalous. Petals clawed, or sessile; imbricate; imbricate-ascending; white, or yellow, or red. Disk present and conspicuous, or absent. The androecium comprising 1–10 members; with united members, or members all free of one another; members markedly unequal (the 2 whorls usually of different lengths); including staminodia, or comprising only fertile stamens. Fertile stamens 1–10. Anthers attached well above the base of the connective; dehiscing longitudinally. Ovary stipitate; free, or eccentric, with the stipe adnate. Stigma dilated. Ovules few, or numerous.

Fruit, seed and seedling. Fruit a two-valved pod; straight (oblong to linear); without markedly twisting or enrolling valves; becoming woody, or not becoming woody (i.e., leathery to woody). Seeds endospermic, or non-endospermic; arillate (the hilum crescentic); with a straight or slightly oblique radicle; amyloid-negative. Cotyledons flat; epigeal, or hypogeal.

Transverse section of lamina. Leaves without conspicuous phloem transfer cells in the minor veins. Druses common in the mesophyll, or 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 common; scabrid, or 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 straight in optical section, or markedly sinuous in high-focus optical section; conspicuously pitted, or not conspicuously pitted. Stomata adaxially common and widespread, or adaxially very rare. Abaxial: Abaxial stomata predominantly paracytic. Abaxial epidermis not papillate. Abaxial interveinal epidermal cell walls straight, or gently undulating; conspicuously pitted in optical section, or not conspicuously pitted in optical section; scarcely staining with safranin, or staining normally with safranin.

Wood anatomy. Wood with septate fibres; storied, or not storied; without normal intercellular canals; without traumatic canals. Intervascular pits very small.

Pollen ultrastructure. Tectum reticulate, or striate; finely to moderately regularly reticulate, or rugulose reticulate, or verrucose reticulate; reticulate striate. Length of colpi greater than one half pole to pole distance, or less than one half pole to pole distance.

Cytology. Basic chromosome number, x = 13, or 14. 2n = 24, or 26, or 28, or 42, or 56.

Species number and distribution. About 100 species. In warm regions.

Tribe. Cercideae.

Comments. Widely cultivated.

Miscellaneous. Illustrations: • B. variegata: Bot. Mag. 111 (1885). • B. galpini: Bot. Mag. 122 (1896). • B. acuminata: Ding Hou, Fl. Malesiana 12 (1995). • B. forficata var. longiflora: Fl. Brasiliensis 15 (1870). • B. holophylla (cf. B. rufa): Fl. Brasiliensis 15 (1870). • B. pulchella: Fl. Brasiliensis 15 (1870). • B. macrantha: Thonner (1915). • B. pauletia: Schery, Ann. Miss. Bot. Gard. 38 (1951). • B. glabra (as standleyi): Schery, Ann. Miss. Bot. Gard. 38 (1951). • B. reflexa: Schery, Ann. Miss. Bot. Gard. 38 (1951). • B. hymenaeifolia (as eucosma): Schery, Ann. Miss. Bot. Gard. 38 (1951). • Floral diagrams of bauhinias: Nat. Pflanzenfam. III (1894). • Sections of winged and undulating Bauhinia stems, with split xylem masses (Solereder, 1908). • B. dipetala, e.m. scanned pollen (Graham & Barker, 1981). • B. aculeata, e.m. scanned pollen (Graham & Barker, 1981). • B. divaricata, e.m. scanned pollen (Graham & Barker, 1981). • B. curtisii, e.m. scanned pollen (Graham & Barker, 1981). • B. integrifolia, 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.’.