| # The Families of Angiosperms |

L. Watson and M.J. Dallwitz

### Oliniaceae Arn. ex Sond.

~ Penaeaceae.

Habit and leaf form. Much branched, small trees, or shrubs. Leaves opposite; without marked odour; simple. Lamina entire; pinnately veined. Leaves vestigially stipulate, or exstipulate. Lamina margins entire. Domatia occurring in the family (found in Olinia); manifested as pits.

Leaf anatomy. Stomata present; anomocytic, paracytic, and cyclocytic. Hairs present; glandular; unicellular. The mesophyll containing crystals. The crystals solitary-prismatic.

Axial (stem, wood) anatomy. Young stems cylindrical, or tetragonal in section. Cork cambium present; initially superficial. Nodes unilacunar. Primary vascular tissues in a cylinder, without separate bundles; bicollateral. Internal phloem present. Secondary thickening developing from a conventional cambial ring. Primary medullary rays narrow.

The wood diffuse porous. The vessels small; radially paired and in radial multiples (in numerous small multiples). The vessel end-walls oblique; simple. The vessels with vestured pits. The axial xylem without tracheids; without fibre tracheids; with libriform fibres; including septate fibres. The fibres without spiral thickening. The parenchyma scanty paratracheal. The secondary phloem not stratified. ‘Included’ phloem absent. The wood not storied.

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

Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’. The ultimate inflorescence units cymose. Inflorescences terminal, or axillary. Flowers small; regular; 4–5 merous; cyclic. Free hypanthium present.

Perianth with distinct calyx and corolla; 8, or 10; 2 whorled; isomerous. Calyx 4, or 5 (represented only by a narrow rim on the hypanthium); 1 whorled; more or less polysepalous; usually more or less 4–5 lobulate, or blunt-lobed, or toothed; regular; not persistent (deciduous). Corolla 4, or 5; 1 whorled; alternating with the calyx (facilitating the identification of the latter); polypetalous; imbricate; regular. Petals spathulate.

Androecium 8–10, or 12–15. Androecial members free of the perianth (on the hypanthium); markedly unequal; free of one another; 2 whorled, or 3 whorled. Androecium including staminodes. Staminodes 4–10; external to the fertile stamens; petaloid, or non-petaloid (comprising a set of hairy, incurved, scalelike, coloured or white antesepalous members alternating with the petals and on the same radii as the fertile stamens, and a set of small antepetalous staminodes (which may be obsolete) alternating with them). Stamens 4, or 5; isomerous with the perianth; oppositisepalous; alternating with the corolla members; filantherous (the filaments short, recurved). Anthers basifixed; non-versatile; dehiscing via longitudinal slits; introrse; bilocular (the thecae distinctly separated on the thickened connective). Endothecium developing fibrous thickenings. Anther wall initially with one middle layer. Tapetum glandular (?). Pollen shed as single grains. Pollen grains aperturate; 3 aperturate, or 6 aperturate; colporate, or colpate and colporate (the colpi alternating with three ‘pseudocolpoid grooves’).

Gynoecium (3–)4 carpelled, or 5 carpelled. Carpels reduced in number relative to the perianth to isomerous with the perianth. The pistil (3–)4–5 celled. Gynoecium syncarpous; eu-syncarpous; inferior. Ovary (3–)4 locular, or 5 locular. Gynoecium stylate. Styles 1; apical. Stigmas 1; capitate. Placentation axile. Ovules (2–)3 per locule; pendulous; apotropous; superposed; hemianatropous; bitegmic; crassinucellate. Outer integument contributing to the micropyle. Embryo-sac development Polygonum-type. Antipodal cells formed; 3 (small); not proliferating; ephemeral. Synergids pear-shaped. Endosperm formation nuclear.

Fruit fleshy; indehiscent; a drupe (or rather, inferior-drupaceous). The drupes with one stone (one seed in each locule). Fruit 3–5 seeded. Seeds non-endospermic. Embryo well differentiated. Cotyledons 2 (spirally twisted or irregularly folded).

Physiology, phytochemistry. Cyanogenic. Cynogenic constituents phenylalanine-derived. Aluminium accumulation not found.

Geography, cytology. Paleotropical and Cape. Sub-tropical to tropical. West and South Africa. X = 10.

Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Myrtiflorae; Myrtales. Cronquist’s Subclass Rosidae; Myrtales. APG III core angiosperms; core eudicot; Superorder Rosanae; malvid. APG IV Order Myrtales (as a synonym of Penaeaceae?).

Species 10. Genera 1; only genus, Olinia.

General remarks. Conspicuously different from Penaeaceae in the perianth, gynoecium, ovule and fruit; see also the compiled data on leaf and stem anatomy, and cytology.

Illustrations. • Olinia capensis and O. usambarensis: Nat. Pflanzenfam. III (1895). • Le Maout and Decaisne: Olinia.

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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