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The families of flowering plants

L. Watson and M.J. Dallwitz

Olacaceae Juss.

Including Aptandraceae Miers, Cathedraceae Van Tiegh., Chaunochitaceae (Chaunochitonaceae) Van Tiegh., Coulaceae Van Tiegh. ex Solander, Harmandiaceae Van Tiegh., Heisteriaceae Van Tiegh., Schoepfiaceae Blume, Scorodocarpaceae Van Tiegh., Strombosiaceae Van Tiegh., Tetrastylidaceae Van Tieghem., Ximeniaceae Van Tiegh.; excluding Octoknemaceae, Erythropalaceae.

Habit and leaf form. Trees, shrubs, and lianas; laticiferous, or non-laticiferous, without coloured juice; resinous, or not resinous. Plants autotrophic, or parasitic; when parasitic, haustorially parasitic; green and photosynthesizing; parasitic on roots of the host (when parasitic). Self supporting, or climbing. Leptocaul. Mesophytic, or xerophytic. Leaves alternate; distichous (commonly), or spiral; ‘herbaceous’ to leathery; petiolate, or subsessile to sessile; non-sheathing; gland-dotted, or not gland-dotted; aromatic, or without marked odour, or foetid; simple. Lamina entire; one-veined, or pinnately veined; cross-venulate. Leaves exstipulate. Lamina margins entire.

General anatomy. Plants with laticifers (these articulated or non-articulated), or without laticifers.

Leaf anatomy. The leaf lamina dorsiventral (usually), or centric (rarely). Stomata variously mainly confined to one surface, or on both surfaces; paracytic (rarely), or anomocytic (?). Hairs present (mostly simple, but dendritic forms recorded in Couleae). Lamina with secretory cavities (in Coulieae), or without secretory cavities. Secretory cavities containing resin; schizogenous. The mesophyll with sclerenchymatous idioblasts (spicular fibres), or without sclerenchymatous idioblasts.

Axial (stem, wood) anatomy. Secretory cavities present (Coulieae), or absent; with resin. Cork cambium present; initially superficial. Nodes unilacunar, or tri-lacunar, or multilacunar (rarely). Primary vascular tissues collateral. Secondary thickening developing from a conventional cambial ring.

The wood diffuse porous. The vessels small (to very small), or medium; solitary, or solitary, radially paired, and in radial multiples. The vessel end-walls scalariform, or simple (usually). The vessels without vestured pits; without spiral thickening. The axial xylem with tracheids, or without tracheids; with vasicentric tracheids (rarely), or without vasicentric tracheids; with fibre tracheids, or without fibre tracheids; with libriform fibres, or without libriform fibres; including septate fibres (rarely), or without septate fibres. The fibres without spiral thickening. The parenchyma apotracheal (typically, exclusively so), or paratracheal (Schoepfia); wood partially storied, or not storied.

Reproductive type, pollination. Plants hermaphrodite, or monoecious, or dioecious.

Inflorescence, floral, fruit and seed morphology. Flowers solitary (in Olax), or aggregated in ‘inflorescences’; when solitary, axillary; when aggregated, in panicles, in racemes, and in heads. Inflorescences axillary. Flowers small; regular; cyclic. Free hypanthium present, or absent. Hypogynous disk present; annular.

Perianth with distinct calyx and corolla (but the calyx lobes reduced); 6–12; 2 whorled; isomerous. Calyx 3–6; 1 whorled; gamosepalous; entire, or lobulate, or blunt-lobed, or toothed; cupuliform; regular; fleshy, or non-fleshy; persistent; accrescent (often), or non-accrescent; imbricate, or open in bud. Corolla 3–6; 1 whorled; polypetalous, or gamopetalous (basally, rarely forming a long tube); valvate; regular; not fleshy.

Androecium 3–6, or 6–12, or 9–18. Androecial members unbranched; free of the perianth, or adnate (to the corolla); free of one another, or coherent; sometimes 1 adelphous (the filaments united basally); 1 whorled. Androecium exclusively of fertile stamens, or including staminodes. Stamens 3–18; reduced in number relative to the adjacent perianth to polystemonous; alternisepalous (when as many as C), or oppositisepalous; alternating with the corolla members, or opposite the corolla members, or both alternating with and opposite the corolla members (?). Anthers basifixed; versatile, or non-versatile; dehiscing via pores, or dehiscing via short slits, or dehiscing via longitudinal slits; tetrasporangiate. Endothecium developing fibrous thickenings. Anther epidermis persistent. Microsporogenesis simultaneous. The initial microspore tetrads tetrahedral, or isobilateral, or decussate. Anther wall initially with more than one middle layer. Tapetum glandular. Pollen grains aperturate; 3 aperturate, or 3–4(–5) aperturate, or 6–8 aperturate; colpate, or porate, or colporate, or foraminate; 2-celled (in Olax and Ximenia).

Gynoecium (2–)3(–5) carpelled. Carpels isomerous with the perianth, or reduced in number relative to the perianth. The pistil 1 celled, or (2–)3(–5) celled. Gynoecium syncarpous; synstylovarious, or eu-syncarpous; superior (usually), or partly inferior. Ovary (2–)3(–5) locular (basally— sometimes unilocular above), or 1 locular. Gynoecium stylate. Styles 1; apical. Stigmas 2–5 lobed. Placentation when unilocular, free central; when plurilocular, axile, or axile to apical. Ovules in the single cavity when unilocular, (2–)3(–5); 1 per locule; pendulous; anatropous; without integuments, or unitegmic, or bitegmic; tenuinucellate, or pseudocrassinucellate. Embryo-sac development Polygonum-type, or Allium-type. Polar nuclei fusing prior to fertilization. Antipodal cells formed; 1–3; not proliferating; ephemeral. Synergids hooked (with filiform apparatus). Endosperm formation cellular, or helobial. Endosperm haustoria present; chalazal.

Fruit fleshy, or non-fleshy; indehiscent; a drupe, or a nut; enclosed in the fleshy hypanthium, or enclosed in the fleshy perianth, or without fleshy investment external to the original ovary. Seeds endospermic. Endosperm oily. Cotyledons 2–6. Embryo chlorophyllous (1/2); straight.

Seedling. Germination phanerocotylar, or cryptocotylar.

Physiology, phytochemistry. Cyanogenic, or not cyanogenic. Alkaloids present, or absent (mostly). Iridoids not detected. Saponins/sapogenins absent (usually). Aluminium accumulation not found (with Octoknema excluded).

Geography, cytology. Sub-tropical to tropical. Pantropical and subtropical. X = 19, 20.

Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Santaliflorae; Santalales. Cronquist’s Subclass Rosidae; Santalales. APG III core angiosperms; core eudicot; Superorder Santalanae. APG IV Order Santalales.

Species 250. Genera 25; Anacolosa, Aptandra, Brachynema, Cathedra, Chaunochiton, Coula, Curupira, Diogoa, Douradoa, Dulacia, Harmandia, Heisteria, Malania, Minquartia, Ochanostachys, Olax, Ongokea, Phanerodiscus, Ptychopetalum, Schoepfia, Scorodocarpus, Strombosia, Strombosiopsis, Tetrastylidium, Ximenia.

Economic uses, etc. Edible fruit from Ximenia (false sandalwood, hog-plum).

Illustrations. • Aptandra tubicina (as A. spruceana): Lindley. • Aptandra tubicina (including spruceana) and A. liriosmoides: Fl. Brasil. 12 (1872–7). • Ptychopetalum olacoides and Chaunochiton loranthoides: Fl. Brasil. 12 (1872–7). • Strombosia pustulata: Hook. Ic. Pl. 23 (1894). • Ximenia americana and X. coriacea: Fl. Brasil. 12 (1872–7). • Cathedra gardneriana (= ?) and C. rubricaulis, Schoepfia brasiliensis (as obliquifolia) and Tetrastylidium grandifolium as brasiliense): Fl. Brasil. 12 (1872–7). • Chaunochiton loranthoides: Hook. Ic. Pl. 11 (1867–71). • Olax durandii: Thonner. • Olax imbricata: Lindley. • Ximenia parviflora: Hook. Ic. Pl. 4 (1841).

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: 15th April 2018.’.