Family Opiliaceae

Opiliaceae Valeton

Including Cansjeraceae J.G. Agardh

Habit and leaf form. Trees and shrubs, or lianas. Plants partially parasitic. Parasitic on roots of the host. Self supporting, or climbing. Mesophytic. Leaves alternate; non-sheathing; simple. Lamina entire (turning a characteristic yellow-green on drying); pinnately veined; cross-venulate. Leaves exstipulate.

Leaf anatomy. Stomata paracytic.

Lamina dorsiventral (usually), or centric. Cystoliths commonly present. The mesophyll containing mucilage cells, or not containing mucilage cells; without calcium oxalate crystals.

Stem anatomy. Cork cambium present; initially superficial. Cortical bundles absent. Medullary bundles absent. Internal phloem absent. Secondary thickening developing from a conventional cambial ring. ‘Included’ phloem absent. Xylem with tracheids, or without tracheids (Lepionurus); with fibre tracheids, or without fibre tracheids. Vessel end-walls simple. Wood parenchyma apotracheal (diffuse).

Reproductive type, pollination. Plants hermaphrodite, or dioecious (infrequently).

Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’; in racemes, in panicles, in spikes, and in umbels. Inflorescences axillary, or cauliflorous. Flowers small; fragrant (at least sometimes), or odourless; regular; 4 merous, or 5 merous; cyclic; tetracyclic. Free hypanthium absent. Hypogynous disk present; of separate members (alternating with the stamens).

Perianth with distinct calyx and corolla, or sepaline (the corolla usually absent in female flowers); 4–5 (female flowers), or 8, or 10; 1 whorled (female flowers), or 2 whorled; isomerous. Calyx 4, or 5; 1 whorled; gamosepalous; lobulate (the lobes sometimes almost obsolete), or blunt-lobed; cupuliform; regular; persistent; non-accrescent; open in bud. Corolla 4, or 5; 1 whorled; polypetalous, or gamopetalous (sometimes basally connate). Corolla lobes markedly longer than the tube. Corolla valvate; regular.

Androecium 4, or 5. Androecial members free of the perianth, or adnate (to the corolla); free of one another; 1 whorled. Androecium exclusively of fertile stamens. Stamens 4, or 5; isomerous with the perianth; nearly always alternisepalous. Anthers dehiscing via longitudinal slits; tetrasporangiate. Endothecium developing fibrous thickenings. Anther epidermis persistent. Microsporogenesis simultaneous. The initial microspore tetrads tetrahedral. Anther wall initially with one middle layer, or initially with more than one middle layer; of the ‘dicot’ type. Tapetum glandular. Pollen grains aperturate; 3 aperturate; colporate (to colporoidate); 2-celled.

Gynoecium 2–5 carpelled. Carpels reduced in number relative to the perianth to isomerous with the perianth. The pistil 1 celled. Gynoecium syncarpous; eu-syncarpous; superior to partly inferior (sometimes half immersed in the disk). Ovary 1 locular. Gynoecium non-stylate, or stylate. Styles attenuate from the ovary; apical; when present, shorter than the ovary. Stigmas 1; sometimes capitate. Placentation basal, or free central. Ovules in the single cavity 1; pendulous (usually), or ascending (rarely, when basal); non-arillate; anatropous; without integuments, or unitegmic; tenuinucellate. Embryo-sac development Polygonum-type. Polar nuclei fusing prior to fertilization. Antipodal cells formed; 3; not proliferating; ephemeral. Synergids hooked (with filiform apparatus). Endosperm formation cellular. Endosperm haustoria present; chalazal.

Fruit fleshy; indehiscent; a drupe. The drupes with one stone. Fruit 1 seeded. Seeds endospermic. Endosperm oily. Seeds without a testa. Embryo well differentiated (though rather small). Cotyledons (2–)3, or 4. Testa lacking.

Seedling. Germination cryptocotylar.

Physiology, biochemistry. Saponins/sapogenins absent.

Geography, cytology. Tropical. Pantropical. X = 10.

Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Myrtiflorae; Myrtales. Cronquist’s Subclass Rosidae; Santalales. APG 3 core angiosperms; core eudicot; Superorder Santalanae; Order Santalales.

Species 28. Genera 10; Agonandra, Cansjera, Champereia, Gjellerupia, Lepionurus, Melientha, Opilia, Pentarhopalopilia, Rhopalopilia, Urobotrya.

Illustrations.
• Technical details: Opilia (Thonner).