| # The Families of Angiosperms |

L. Watson and M.J. Dallwitz

### Uapacaceae (Muell. Arg.) Airy Shaw

~ Euphorbiaceae.

Habit and leaf form. Trees, or shrubs; non-laticiferous, without coloured juice; more or less pachycaul (the leaves crowded towards the branch tips). Leaves alternate; simple. Lamina entire; more or less cuneate obovate. Leaves stipulate.

General anatomy. Plants without laticifers.

Axial (stem, wood) anatomy. Secondary thickening developing from a conventional cambial ring.

The vessel end-walls simple. The vessels without vestured pits. The parenchyma paratracheal (and some scattered cells).

Reproductive type, pollination. Unisexual flowers present. Plants dioecious. Gynoecium of male flowers pistillodial (large, obconical, funnel- or mushroom-shaped, sometimes lobed).

Inflorescence, floral, fruit and seed morphology. Flowers solitary (female), or aggregated in ‘inflorescences’ (male); those of the male inflorescences in heads (these globular, capitate, pedunculate). Inflorescences and the solitary female flowers with involucral bracts (those of the male inflorescences 5–10, large, much imbricate); those of male flowers pseudanthial (the involucre calycine). Free hypanthium absent. Hypogynous disk absent.

Perianth sepaline (in the male flowers), or vestigial (in female flowers); in the male flowers, 5–6; 1 whorled. Calyx of male flowers 5–6 (in female flowers, more or less sinuous or truncate); 1 whorled; gamosepalous; entire to lobulate (female flowers), or lobulate, or blunt-lobed, or toothed (male flowers); in male flowers, more or less campanulate (or turbinate).

Androecium of male flowers 4–6, or 8–12. Androecial members free of the perianth; free of one another; 1 whorled. Androecium exclusively of fertile stamens, or including staminodes. Staminodes when present, 4–6 (pilose, alternating with the stamens). Stamens 4–6; isomerous with the perianth; oppositisepalous; erect in bud. Anthers introrse. Pollen grains aperturate; 3(–4) aperturate; colporate.

Gynoecium (2–)3(–4) carpelled. Carpels reduced in number relative to the perianth, or isomerous with the perianth. The pistil (2–)3(–4) celled. Gynoecium syncarpous; synovarious; superior. Ovary (2–)3(–4) locular. Gynoecium stylate. Styles (2–)3(–4); free (thick, laciniate, recurved); apical. Placentation apical. Ovules 2 per locule; pendulous.

Fruit fleshy; indehiscent; a drupe. The drupes with separable pyrenes (these usually three, dorsally bisulcate). Seeds endospermic (the endosperm fleshy).

Physiology, phytochemistry. Inulin not found.

Geography, cytology. Paleotropical. Tropical. Tropical Africa, Madagascar.

Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Malviflorae; Euphorbiales. Cronquist’s Subclass Rosidae; Euphorbiales. APG III core angiosperms; core eudicot; Superorder Rosanae; fabid. APG IV Order Malpighiales (as a synonym of Euphorbiaceae).

Species 50. Genera 1; only genus, Uapaca.

General remarks. “Hitherto included in Euphorbiaceae, but foliage, inflorescence and anatomy aberrant”: Airy Shaw (1973). Relevant comparative anatomical data have not been located, and the attempt at compiling comparative data for these descriptions shows no clear distinction between Uapaca and Euphorbiaceae sensu stricto (q.v.).

Illustrations. • Uapaca guineensis: Hook. Ic. Pl. 13 (1877–79). • Uapaca ferruginea, U. louvelii, U. sambiranensis: Humbert, Fl. Madagascar and Comores 1 (1958).

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, genera included in each family, and classifications (Dahlgren; Dahlgren, Clifford, and Yeo; Cronquist; APG). See also Guidelines for using data taken from Web publications.

Cite this publication as: ‘Watson, L., and Dallwitz, M.J. 1992 onwards. The families of flowering plants: descriptions, illustrations, identification, and information retrieval. Version: 8th June 2026. delta-intkey.com’.

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