The genera of Leguminosae-Caesalpinioideae & Swartzieae
Exostylis G. Don
Type species: E. venusta Schott ex Spreng.
Habit and leaf form. Small trees; unarmed.
Phyllotaxy spiral. The leaves compound; pinnate; imparipinnate. The leaflets alternate (often toothed or crenulate); petiolulate to sessile to sub-sessile; 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 (caducous); small, subulate-setaceous. Stipels present (subulate).
Inflorescence and floral morphology. The inflorescences axillary; short, lax simple racemes. The flowers not distichous. Bracts setaceous or acuminate, persistent beyond anthesis. Bracteoles present (setaceous or acuminate); small, not enclosing the flower buds; persistent beyond anthesis; not valvate.
The flowers hermaphrodite; not pentamerous throughout; departing from pentamery in the calyx; coloured. Floral tube length relative to total hypanthium + calyx length about 0.25. Hypanthium present; cupular. The perianth comprising distinct calyx and corolla. Calyx 3–4 (valvately partite); Swartzieae type (closed before flowering, splitting more or less irregularly into valvate lobes or teeth); gamosepalous; more or less regular to markedly irregular; members not imbricate. Corolla present; slightly irregular; 5; without greatly reduced members; polypetalous. Petals clawed, or sessile; imbricate; imbricate-ascending (the adaxial member within the other four, which are often convolute); red. Disk absent. 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 at the base of the connective; dehiscing longitudinally. Ovary long stipitate; free. Stigma not dilated. Ovules few to numerous.
Fruit, seed and seedling. Fruit a two-valved pod; straight; obliquely ovate, compressed, leathery, not becoming woody. Seeds not arillate; with an inflexed radicle; amyloid-negative; with starch.
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 not seen. No compound or branched eglandular hairs seen. Capitate glands not seen. Expanded and embedded hair-feet absent. Adaxial: Adaxial interveinal epidermal cell walls straight in optical section; not conspicuously pitted; thin. Stomata adaxially very rare. Abaxial: Abaxial stomata not predominantly paracytic (mixed anomcytic, actinocytic, cyclocytic). Abaxial epidermis not papillate. Abaxial interveinal epidermal cell walls straight, or gently undulating; not conspicuously pitted in optical section; staining normally with safranin; thin.
Pollen ultrastructure. Tectum papillate; reticulate papillate. Length of colpi less than one half pole to pole distance.
Species number and distribution. 4 species (E. amazonica, E. glabra, E. godoyensis and E. venusta). Brazil.
Tribe. Papilionoideae-Exostyleae (former Swartzieae).
Miscellaneous. Illustrations: • Exostyles venusta: Fl. Brasiliensis 15 (1870).
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. delta-intkey.com/caes’.