| # The genera of Leguminosae-Caesalpinioideae and Swartzieae |

L. Watson and M.J. Dallwitz

### Isoberlinia Craib & Stapf

Type species: I. tomentosa (Harms) Craib & Stapf (I. dalzielii Craib & Stapf).

Habit and leaf form. Trees; unarmed.

Phyllotaxy spiral. The leaves compound; pinnate; paripinnate. The leaflets few per leaf (2–5 pairs); opposite or sub-opposite; petiolulate; without noticeably twisted petiolules; markedly asymmetrical to symmetrical or nearly so; pinnately veined, with a predominant ‘midrib’; without a continuous marginal nerve. Stipels absent.

Inflorescence and floral morphology. The inflorescences terminal; branched; of racemose units; panicles (of racemes). The flowers not distichous. Bracts small, caducous, absent at anthesis. Bracteoles present; relatively large and enclosing the flower buds; persistent beyond anthesis; concave, valvate; free.

The flowers hermaphrodite; pentamerous, or not pentamerous throughout (rarely); departing from pentamery when not pentamerous, in the calyx, or in the androecium; white or green. Floral tube length relative to total hypanthium + calyx length about 0.25. Hypanthium present; cupular, or tubular. The perianth comprising distinct calyx and corolla. Calyx 5, or 6 (rarely); polysepalous; more or less regular. Corolla present; scarcely exceeding the sepals, regular to slightly irregular (the adaxial member usually rather broader); 5; without greatly reduced members; polypetalous. Petals sessile; imbricate. Disk absent. The androecium comprising 10–13 members; not declinate; members all free of one another; members all more or less equal in length; comprising only fertile stamens. Fertile stamens 10(–13). Anthers attached well above the base of the connective; dehiscing longitudinally. Ovary stipitate; eccentric, with the stipe adnate (the style filiform). Stigma not dilated. Ovules numerous.

Fruit, seed and seedling. Fruit a two-valved pod (elastically dehiscent); valves twisting and enrolling during dehiscence; obliquely oblong, compressed, becoming woody. The mature valves with conspicuous, prominent, raised venation; conspicuous venation not predominantly longitudinal. Seeds not arillate; with a straight or slightly oblique radicle; amyloid-positive. Cotyledons not flat; of Type 4; with a vascular system ramified throughout; hypogeal.

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), or 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 common, or not seen; scabrid. 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 present; (at least some of them) thin-walled; hair feet (at least some of them) complex with vertical walls, or all simple, without vertical walls. Adaxial: Adaxial interveinal epidermal cell walls straight in optical section, or markedly sinuous in high-focus optical section; not conspicuously pitted. Stomata adaxially common and widespread. Abaxial: Abaxial stomata predominantly paracytic. Abaxial epidermis not papillate. Abaxial interveinal epidermal cell walls markedly sinuous in high-focus optical section; conspicuously pitted in optical section, or not conspicuously pitted in optical section; staining normally with safranin; thin.

Pollen ultrastructure. Tectum striate; pole to pole striate. Length of colpi greater than one half pole to pole distance.

Species number and distribution. 5 species (I. angolensis, I. doka and I. paradoxa, plus I. scheffleri and I. tomentosa transferred from Berlinia). Tropical Africa.

Tribe. Detarieae (Amherstieae of Cowan and Polhill 1981); Amherstieae clade of Bruneau et al. (2008).

Miscellaneous. Illustrations: • Isoberlinia doka: Hook. Ic. Pl. 31 (1922). • I. doka and I. tomentosa: Aubréville, Flore du Cameroun (1970).

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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