| # The genera of Leguminosae-Caesalpinioideae and Swartzieae |

L. Watson and M.J. Dallwitz

### Oxystigma Harms

Eriander Winkler, Pterygopodium Harms

Type species: O. mannii (Baill.) Harms.

Habit and leaf form. Trees; unarmed.

Phyllotaxy distichous, or spiral. The leaves compound; pinnate; imparipinnate, or paripinnate. The leaflets leathery, few per leaf ((1-)2–3 pairs); opposite or sub-opposite, or alternate; petiolulate; without noticeably twisted petiolules; symmetrical or nearly so; pinnately veined, with a predominant ‘midrib’; without a continuous marginal nerve. Stipules absent or early caducous or very inconspicuous in mature leaves; membranous. Stipels absent.

Inflorescence and floral morphology. The inflorescences branched; of racemose units; panicles (of elongated, slender racemes). The flowers not distichous. Bracts minute, caducous absent at anthesis. Bracteoles present; small, not enclosing the flower buds (minute and scalelike, at the bases of the flowers); absent at anthesis; not valvate; free.

The flowers small; hermaphrodite; not pentamerous throughout; departing from pentamery in the corolla, or in the calyx and in the corolla (rarely). Hypanthium more or less absent, the androecium hypogynous. The perianth exclusively sepaline (but petaloid). Calyx 5, or 6 (rarely); covering the rest of the flower in bud; polysepalous; more or less regular (the orbicular, petal-like segments subequal); members broadly imbricate. Corolla absent. Disk present and conspicuous (fleshy, slightly embedded in hypanthium). The androecium comprising 10 members; not declinate; members all free of one another (with filiform filaments); members all more or less equal in length; comprising only fertile stamens. Fertile stamens (8–)10. Anthers attached well above the base of the connective; dehiscing laterally; dehiscing longitudinally. Ovary sessile or subsessile (the style shortish and subulate); free. Stigma not dilated. Ovules few, or solitary (1–2).

Fruit, seed and seedling. Fruit one-seeded, indehiscent; drupaceous; rounded-obovate and corrugated, or flat and winglike with the seed distal; winged proximally to the single seed (with a proximal wing), or not noticeably winged; becoming woody. The mature valves with conspicuous, prominent, raised venation; conspicuous venation predominantly longitudinal. Seeds not arillate; with a straight or slightly oblique radicle; amyloid-negative. Cotyledons hypogeal.

Transverse section of lamina. Leaves with conspicuous phloem transfer cells in the minor veins. Druses absent from the mesophyll. Mesophyll secretory cavities (gland-dots) common; epithelium-lined. Adaxial hypodermis absent. Leaf girders absent. Laminae dorsiventral. Mesophyll exhibiting fibres or sclereids which are unaligned with the vascular bundles. 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 markedly sinuous in high-focus optical section; conspicuously pitted; thick. Stomata adaxially very rare. Abaxial: Abaxial stomata predominantly paracytic. Abaxial epidermis papillate interveinally; with papillae over-arching the stomata. Abaxial interveinal epidermal cell walls markedly sinuous in high-focus optical section; conspicuously pitted in optical section; staining normally with safranin; of medium thickness.

Wood anatomy. Wood without septate fibres; not storied; with normal intercellular canals, or without normal intercellular canals; with traumatic canals, or without traumatic canals. Intervascular pits medium to large.

Species number and distribution. 5 species (O. buchholzii, O. gilbertii, O. mannii, O. msoo, O. oxyphyllum). Tropical Africa.

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

Miscellaneous. Illustrations: • Oxystigma msoo: Brenan, Fl. Tropical East Africa (1967). • O. buchholzii, with Polystemonanthus and Cyanothyrsus (= Daniellia): Engler, Bot. Jahrb. 26. • Oxystigma mannii: Engler & Drude, Pflanzenwelt Afrikas 9 (1915). • O. oxyphyllum (as Pterygopodium), with Hylodendron gabunense): Aubréville, Flore du Gabon (1968). • Oxystigma buchholzii: TS leaflet.

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: 4th August 2019. delta-intkey.com’.

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