| # The Families of Angiosperms |

L. Watson and M.J. Dallwitz

### Irvingiaceae Pierre

~ Simaroubaceae, Ixonanthaceae.

Habit and leaf form. Trees. Leaves alternate; leathery; without marked odour; simple. Lamina entire; lanceolate, or oblong, or ovate; pinnately veined; cross-venulate. Leaves conspicuously stipulate. Stipules intrapetiolar (large or very long, embracing the terminal buds); free of one another; folded and caducous.

Leaf anatomy. The leaf lamina dorsiventral. Extra-floral nectaries absent. Abaxial epidermis papillose, or not papillose. Mucilaginous epidermis present. Stomata mainly confined to one surface (abaxial); anomocytic, or paracytic. Adaxial hypodermis absent. The mesophyll containing mucilage cells; with sclerenchymatous idioblasts; containing crystals. The crystals solitary-prismatic (abundantly), or druses.

Axial (stem, wood) anatomy. Secretory cavities present; with mucilage. Cork cambium present; initially deep-seated. Primary vascular tissues in a cylinder, without separate bundles; collateral. Secondary thickening developing from a conventional cambial ring.

The vessel end-walls simple. The axial xylem without fibre tracheids. The parenchyma apotracheal, or paratracheal.

Reproductive type, pollination. Unisexual flowers absent. Plants hermaphrodite.

Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’; in panicles. Inflorescences terminal and axillary. Flowers bracteate (the bracts very small); small; regular; 5 merous; pentacyclic, or polycyclic. Free hypanthium absent. Hypogynous disk present; intrastaminal; conspicuous, fleshy, cupular.

Perianth with distinct calyx and corolla; 10; 2 whorled; isomerous. Calyx 5; 1 whorled; polysepalous; regular; imbricate. Corolla 5; 1 whorled; polypetalous; imbricate; regular.

Androecium (9–)10. Androecial members free of the perianth; free of one another; 1 whorled, or 2 whorled (?). Stamens (9–)10; isomerous with the perianth (usually), or reduced in number relative to the adjacent perianth; filantherous. Anthers dorsifixed to basifixed (sub-basifixed); dehiscing via longitudinal slits.

Gynoecium (4–)5 carpelled, or 2 carpelled. Carpels reduced in number relative to the perianth, or isomerous with the perianth. The pistil (4–)5 celled, or 2 celled. Gynoecium syncarpous; eu-syncarpous; superior. Ovary (4–)5 locular, or 2 locular; sessile. Gynoecium stylate. Styles 1; attenuate from the ovary; apical. Stigmas 1. Placentation axile to apical. Ovules 1 per locule; funicled; hemianatropous, or anatropous (?); crassinucellate.

Fruit fleshy, or non-fleshy; indehiscent; a drupe (one celled, or 4–5 celled), or a samara (bilocular). Seeds thinly endospermic, or non-endospermic. Cotyledons 2; flat (face to face).

Geography, cytology. Paleotropical. Tropical. Tropical Africa, tropical E. Asia.

Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Rutiflorae; Rutales. Cronquist’s Subclass Rosidae; Sapindales. APG III core angiosperms; core eudicot; Superorder Rosanae; fabid. APG IV Order Malpighiales.

Species about 20. Genera 3; Desbordesia, Irvingia, Klainedoxa.

General remarks. Sound practical taxonomic applications of recent notions on the dispositions of assorted genera previously referred to Simaroubaceae will necessitate thorough overhaul of family descriptions as compiled in this package (cf. Ixonanthaceae, Kirkiaceae, Picramniaceae, Simaroubaceae, Surianaceae, Stylobasiaceae).

Economic uses, etc. Butters (Dika bread, cay-cay etc.) from the seeds — e.g. of Irvingia barteri.

Illustrations. • Irvingia barteri: Thonner. • Irvingia gabonensis, as I. barteri: Hook. Ic. Pl. 13 (1877–79). • Irvingia malayana: Hook. Ic. Pl. 13 (1877–79).

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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