| # The genera of Leguminosae-Caesalpinioideae and Swartzieae |

L. Watson and M.J. Dallwitz

### Zenkerella Taub.

Cynometra spp.

Type species: Z. citrina Taub.

Habit and leaf form. Trees, or shrubs; unarmed.

Phyllotaxy spiral. The leaves ostensibly simple; pinnately veined, with a predominant midrib. Stipules present, persistent and conspicuous in mature leaves (rarely), or absent or early caducous or very inconspicuous in mature leaves; large and leafy, or membranous (usually); not connate.

Inflorescence and floral morphology. The inflorescences axillary; branched; of racemose units; fascicles (of racemes). The flowers not distichous. Bracteoles present; small, not enclosing the flower buds; caducous, absent at anthesis; not valvate; free.

The flowers hermaphrodite; pentamerous, or not pentamerous throughout; departing from pentamery in the calyx; coloured. Floral tube length relative to total hypanthium + calyx length about 0.25. Hypanthium present; eccentically campanulate. The perianth comprising distinct calyx and corolla. Calyx 4, or 5 (rarely); covering the rest of the flower in bud; not Swartzieae type; polysepalous (the sepals reflexed); members imbricate. Corolla present; regular to slightly irregular; 5; without greatly reduced members; polypetalous. Petals subequal, imbricate; imbricate-ascending. Disk absent. The androecium comprising 10 members; not declinate; with united members (shortly so at their bases), or members all free of one another; members all more or less equal in length; comprising only fertile stamens. Fertile stamens 10. Anthers attached well above the base of the connective; dehiscing longitudinally. Ovary stipitate; eccentric, with the stipe adnate. Stigma dilated (mushroom-shaped or capitate). Ovules few, or solitary (1–3).

Fruit, seed and seedling. Fruit a two-valved pod; without markedly twisting or enrolling valves; stipitste, almost suborbicular, not becoming woody. The mature valves leathery, with conspicuous, prominent, raised venation; conspicuous venation transverse, not predominantly longitudinal. Seeds not arillate; with a straight or slightly oblique radicle.

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 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 common. 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. Adaxial: Adaxial interveinal epidermal cell walls markedly sinuous in high-focus optical section; conspicuously pitted; medium-thick. Stomata adaxially very rare. Abaxial: Abaxial stomata predominantly paracytic (some cyclocytic). Abaxial epidermis not papillate. Abaxial interveinal epidermal cell walls straight, or gently undulating; conspicuously pitted in optical section; staining normally with safranin; thin.

Species number and distribution. 5 species. Tropical Africa.

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

Miscellaneous. Illustrations: • Zenkerella egregia and Z. grotei: Brenan, Fl. Tropical East Africa (1967). • Zenkerella citrina, with Didelotia spp.: Aubréville, Flore du Gabon (1968).

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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