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The families of flowering plants

L. Watson and M.J. Dallwitz

Onagraceae Juss.

Including Circaeaceae Lindl., Epilobiaceae Ventenat, Jussieuaceae Drude, Oenothereae (Oenotheraceae) Endl., Onagrariaceae Dulac

Habit and leaf form. Shrubs and herbs, or trees (rarely, to 30 m); bearing essential oils, or without essential oils. Annual, or biennial, or perennial; with a basal aggregation of leaves, or without conspicuous aggregations of leaves. Hydrophytic, or helophytic, or mesophytic; when hydrophytic (Ludwigia), rooted. Leaves of Ludwigia emergent and floating. Leaves alternate, or opposite, or whorled; when alternate, spiral; petiolate to sessile; non-sheathing; simple; epulvinate. Lamina dissected, or entire; when dissected, pinnatifid; pinnately veined; cross-venulate. Leaves stipulate, or exstipulate. Stipules when present, intrapetiolar; free of one another; caducous. Leaf development not ‘graminaceous’.

Leaf anatomy. The leaf lamina dorsiventral, or centric. Mucilaginous epidermis present, or absent. Stomata mainly confined to one surface (then usually abaxial, but occasionally adaxial), or on both surfaces; anisocytic, or tetracytic, or cyclocytic. Hairs present; all or mostly eglandular (?); nearly always simple, unicellular, or multicellular. Unicellular hairs simple (variously shaped, often clavate). Multicellular hairs long or short uniseriate; simple. Complex hairs absent. Lamina with secretory cavities (occasionally), or without secretory cavities. The mesophyll without sclerenchymatous idioblasts; containing crystals. The crystals raphides (very commonly, these sometimes accompanied or replaced by mucilage), or druses, or raphides and druses. Minor leaf veins without phloem transfer cells (6 genera).

Axial (stem, wood) anatomy. Pith often becoming hollow. Cork cambium present; initially deep-seated. Nodes unilacunar. Primary vascular tissues in a cylinder, without separate bundles; usually bicollateral. Internal phloem usually present. Cortical bundles absent. Medullary bundles absent. Secondary thickening developing from a conventional cambial ring, or anomalous. The anomalous secondary thickening via concentric cambia (?), or from a single cambial ring. Primary medullary rays narrow.

The wood diffuse porous. The vessels very to moderately small; solitary, radially paired, in radial multiples, and clustered. The vessel end-walls horizontal to oblique; simple (usually), or reticulately perforated (rarely). The vessels with vestured pits, or without vestured pits; without spiral thickening. The axial xylem without fibre tracheids; with libriform fibres; at least sometimes including septate fibres, or without septate fibres (?). The fibres without spiral thickening. The parenchyma very scanty paratracheal. ‘Included’ phloem present (commonly), or absent. The wood partially storied. Tyloses present, or absent.

Reproductive type, pollination. Plants hermaphrodite (usually), or monoecious (occasionally, e.g. in Fuchsia). Pollination anemophilous, or entomophilous.

Inflorescence, floral, fruit and seed morphology. Flowers solitary, or aggregated in ‘inflorescences’; when aggregated, in panicles, or in racemes, or in spikes. Inflorescences terminal, or axillary. Flowers small to large; regular to very irregular; (2–)4(–7) merous; cyclic; tricyclic, or tetracyclic, or pentacyclic. Free hypanthium usually present (usually elongated).

Perianth with distinct calyx and corolla (usually), or sepaline (the corolla sometimes absent); 4–8(–14); 1 whorled, or 2 whorled; isomerous. Calyx (2–)4(–7); 1 whorled; gamosepalous; blunt-lobed; lobes valvate. Corolla (2–)4(–7) (rarely absent); 1 whorled; polypetalous; imbricate, or contorted; yellow, or pink, or purple. Petals clawed (often), or sessile; often bilobed (or trilobed).

Androecium 8 (often), or 8–10, or 4, or 2, or 1. Androecial members adnate (to the hypanthium), or free of the perianth (on the disk); all equal, or markedly unequal; free of one another; 2 whorled (often), or 1 whorled. Androecium exclusively of fertile stamens, or including staminodes. Staminodes when present, 1, or 2–4; petaloid (Lopezia), or non-petaloid. Stamens (1–)8(–10); reduced in number relative to the adjacent perianth (rarely), or isomerous with the perianth, or diplostemonous. Anthers dorsifixed; versatile; dehiscing via longitudinal slits; introrse; tetrasporangiate. Microsporogenesis simultaneous. The initial microspore tetrads tetrahedral. Pollen shed in aggregates, or shed as single grains; with viscin strands (often), or without viscin strands; when in aggregates, in tetrads. Pollen grains aperturate; (2–)3(–6) aperturate; colpate, or porate (often), or colporate; 2-celled (in Clarkia, Epilobium and Oenothera).

Gynoecium 4(–7) carpelled. Carpels isomerous with the perianth. The pistil 2 celled, or 4–7 celled. Gynoecium syncarpous; synstylovarious, or eu-syncarpous; inferior, or partly inferior. Ovary 4(–7) locular (when inferior — but the septa often imperfect below), or 2 locular (when half-inferior). Epigynous disk present. Gynoecium stylate. Styles 1; apical. Stigmas 1–4; wet type, or dry type; papillate, or non-papillate; Group II type, or Group III type, or Group IV type. Placentation axile, or parietal. Ovules 1–50 per locule (to ‘many’); pendulous, or ascending; non-arillate; anatropous; bitegmic; crassinucellate. Outer integument contributing to the micropyle. Embryo-sac development Oenothera-type. Antipodal cells not formed. Synergids with filiform apparatus. Hypostase commonly present. Embryogeny onagrad.

Fruit fleshy (rarely), or non-fleshy; dehiscent, or indehiscent; a capsule (usually), or a berry, or a nut. Capsules loculicidal, or septicidal. Fruit 2–100 seeded (usually ‘many’). Seeds non-endospermic; conspicuously hairy (sometimes, with a tuft, in Epilobium), or not conspicuously hairy. Cotyledons 2. Embryo achlorophyllous (5/5); straight.

Seedling. Germination phanerocotylar.

Physiology, phytochemistry. C3. C3 physiology recorded directly in Calylophus, Epilobium, Gaura, Oenothera. Anatomy non-C4 type (Calylophus, Epilobium, Gaura, Oenothera). Sugars transported as oligosaccharides + sucrose (in Hauya). Cyanogenic, or not cyanogenic. Alkaloids absent (32 species). Iridoids not detected. Saponins/sapogenins absent. Proanthocyanidins present (very rarely), or absent; in a species of Jussieua delphinidin. Flavonols present (usually); quercetin, or kaempferol and quercetin, or quercetin and myricetin. Ellagic acid present (11 species, 8 genera). Ursolic acid present. Aluminium accumulation not found.

Geography, cytology. Frigid zone to tropical. Cosmopolitan, except in arid parts of Australia and Africa. X = (6-)7(-18). Supposed basic chromosome number of family: 11 (?).

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.

Species 640. Genera about 20; Boisduvallia, Calylophus, Camissonia, Circaea, Clarkia, Epilobium, Eremothera, Fuchsia, Gaura, Gayophytum, Gongylocarpus, Hauya, Jussiaea (= Ludwigia), Lopezia, Ludwigia, Oenothera, Stenosiphon, Xylonagra.

Economic uses, etc. Most genera include species cultivated as ornamentals, with Fuchsia contributing many. Fuchsia berries are edible and good.


The Conium there, her stalks bedropp’d with red,
Rears, with Circaea, neighbour of the dead
(Charlotte Smith, quoted by Ann Pratt, ‘Wild Flowers’ (1857) - Circaea lutetiana)

Illustrations. • Le Maout and Decaisne: Epilobium, Isnardia (= Ludwigia). • Le Maout and Decaisne: Circaea, Fuchsia, Jussieua (= Ludwigia). • Ludwigia linifolia: Thonner. • Epilobium, Circaea (B. Ent. compilation). • Epilobium confertifolium: Hook. Ic. Pl. 7–8 (1844). • Chamerion dodonaei (= Epilobium): Bot. Mag. 76, 1789. • Circaea lutetiana: Eng. Bot. 511 (1865). • Clarkia rhomboidea, C. elegans and C. pulchella: Bot. Reg. 1981, 1837. • Epilobium billardiereanum: Hooker, Fl. Tasmaniae (1860). • Epilobium hirsutum: Eng. Bot. 497 (1865). • Epilobium lanceolatum: Eng. Bot. 500 (1865). • Eremothera boothii sub-sp. alyssoides, as Oenothera: Hook. Ic. Pl. 4 (1841). • Eucharidium concinnum: Bot. Reg. 1962, 1837. • Fuchsia fulgens: Bot. Reg. XXIV, 1 (1838). • Fuchsia magellanica: Bot. Mag. 97, 1789. • Fuchsia microphylla: Bot. Reg. 1269. • Fuchsia cf. parviflora: as F. cylindracea, Bot. Reg. XXIV, 66 (1838). • Fuchsia thymifolia: Bot. Reg. 1284 (1829). • Ludwigia palustris: Eng. Bot. 510 (1865). • Oenothera anomala: Bot. Mag. 1797. • Oenothera decumbens: as Godetia lepida, Bot. Reg. 1849 (1836). • Oenothera rosea: Bot. Mag. 347, 1796. • Oenothera perennis: Bot. Mag. 355, 1796.

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.’.