Family Irvingiaceae

Irvingiaceae Pierre

~ Simaroubaceae, Ixonanthaceae

Habit and leaf form. Trees; non-laticiferous and without coloured juice. Leaves alternate; leathery; not gland-dotted; simple. Lamina entire; lanceolate, or oblong, or ovate; pinnately veined. Leaves conspicuously stipulate. Stipules intrapetiolar (large or very long, embracing the terminal buds); free of one another; folded and caducous.

Leaf anatomy. 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. Lamina dorsiventral. The mesophyll containing mucilage cells; with sclerencymatous idioblasts; containing calcium oxalate crystals. The mesophyll crystals solitary-prismatic (abundantly), or druses.

Stem anatomy. Secretory cavities present; with mucilage. Cork cambium present; initially deep-seated. Secondary thickening developing from a conventional cambial ring. Xylem without fibre tracheids. Vessel end-walls simple. Wood 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; neither papilionaceous nor pseudo-papilionaceous; 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); without fleshy investment. Seeds thinly endospermic, or non-endospermic; with a testa. 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 3 core angiosperms; core eudicot; Superorder Rosanae; fabid; Order Malpighiales.

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

Note that satisfactory representation of recent notions on the proper dispositions of genera previously referred to Simaroubaceae will necessitate thorough overhaul of the descriptions presented in this package (cf. Kirkiaceae, Picramniaceae, Surianaceae, Stylobasiaceae).

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

Illustrations.
• Technical details: Irvingia (Thonner).