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The families of flowering plants

L. Watson and M.J. Dallwitz

Rutaceae Juss.

Including Amyrideae (Amyridaceae) R. Brown, Aurantiaceae Juss., Boroniaceae J.G. Agardh, Correaceae J.G. Agardh, Cuspariaceae J.G. Agardh, Dictamnaceae von Vest, Diosmeae (Diosmaceae) R. Br., Diplolaenaceae J.G. Agardh, Fraxinellae, (Fraxinellaceae) Nees & Mart., Pilocarpeae, (Pilocarpaceae) J.G. Agardh, Pteleaceae Kunth, Sarcodiscaceae Dulac, Zanthoxylaceae Nees & Mart. corr. Bartl.; excluding Cneoraceae, Flindersiaceae, Ptaeroxylaceae, Rhabdodendraceae.

Habit and leaf form. Trees and shrubs (mostly), or herbs (Rutieae); bearing essential oils. ‘Normal’ plants, or switch-plants (sometimes with spines); sometimes with the principal photosynthesizing function transferred to stems, or phyllodineous. Leaves well developed, or much reduced. Mesophytic, or xerophytic. Leaves persistent, or deciduous; alternate, or opposite; usually spiral; ‘herbaceous’, or leathery; petiolate; non-sheathing; nearly always gland-dotted (exceptions: Leptothyrsa, Phellodendron); aromatic; simple, or compound (usually); when compound (i.e. usually) ternate, or pinnate, or bipinnate, or unifoliolate. Lamina when simple dissected, or entire; sometimes linear (and ericoid); when simple/dissected pinnatifid, or much-divided; pinnately veined, or one-veined. Leaves exstipulate (usually), or stipulate (rarely). Stipules when present, intrapetiolar; represented by glands. Leaf development not ‘graminaceous’. Domatia occurring in the family (known from 3 genera); manifested as pockets.

Leaf anatomy. The leaf lamina dorsiventral (usually), or centric. Extra-floral nectaries seemingly absent. Mucilaginous epidermis present, or absent. Stomata mainly confined to one surface, or on both surfaces; exhibiting various arrangements of subsidiaries. Hairs present, or absent (infrequent in many family members, but assorted glandular and eglandular forms occur). Lamina “almost always” with secretory cavities. Secretory cavities containing oil; variously interpreted as schizogenous, or lysigenous. The mesophyll with sclerenchymatous idioblasts, or without sclerenchymatous idioblasts; commonly containing crystals. The crystals raphides, or solitary-prismatic. Minor leaf veins without phloem transfer cells (5 genera).

Axial (stem, wood) anatomy. Secretory cavities very often present (but sometimes replaced by secretory cells); with oil. Cork cambium present; initially superficial. Nodes unilacunar, or tri-lacunar. Primary vascular tissues in a cylinder, without separate bundles (mostly), or in a cylinder, without separate bundles to comprising a ring of bundles (a few with relatively broad primary rays in very young stems); collateral. Internal phloem absent. Cortical bundles present (e.g., in Eriostemon), or absent. Secondary thickening developing from a conventional cambial ring.

The wood variousy ring porous, or semi-ring porous, or diffuse porous. The vessels small to medium; typically radially paired to in radial multiples, or in tangential arcs (sometimes). The vessel end-walls typically simple (save for rare multiperforate plates seen in a few species). The vessels without vestured pits; with spiral thickening, or without spiral thickening. The axial xylem with tracheids, or without tracheids; with vasicentric tracheids (rarely), or without vasicentric tracheids; without fibre tracheids; with libriform fibres; including septate fibres (rarely), or without septate fibres. The parenchyma apotracheal, or paratracheal (rarely absent). ‘Included’ phloem absent. The wood storied (Chloroxylon), or partially storied (?), or not storied (?).

Reproductive type, pollination. Plants hermaphrodite (usually), or monoecious, or andromonoecious (rarely), or dioecious, or polygamomonoecious. Pollination entomophilous.

Inflorescence, floral, fruit and seed morphology. Flowers solitary (rarely), or aggregated in ‘inflorescences’; in cymes, in panicles, in racemes, and in corymbs. The ultimate inflorescence units cymose (usually), or racemose. Inflorescences terminal, or axillary, or epiphyllous (rarely). Flowers bracteate; small to medium-sized; commonly fragrant; regular (usually), or somewhat irregular. The floral irregularity when noticeable, involving the perianth and involving the androecium (not K). Flowers mostly (3–)5 merous; cyclic. Floral receptacle developing a gynophore (associated with the disk), or with neither androphore nor gynophore. Free hypanthium absent. Hypogynous disk present; intrastaminal; annular (sometimes one-sided), or of separate members (e.g. in Coleonema).

Perianth with distinct calyx and corolla (but the calyx sometimes minute and inconspicuous); (3–)6, or (6–)10; 2 whorled; isomerous. Calyx (3–)4, or 5; 1 whorled; polysepalous, or gamosepalous (basally); regular; imbricate, or valvate (e.g. Boronia, Correa); with the median member posterior. Corolla (3–)4, or 5; 1 whorled; polypetalous, or gamopetalous; imbricate, or valvate (the odd member anterior); regular, or unequal but not bilabiate.

Androecium 2, or 3, or 5, or 8, or 10, or 20–60. Androecial members unbranched, or branched (by the splitting of simple primordia, e.g. in Citrus); free of the perianth; all equal, or markedly unequal; free of one another, or coherent (the filaments usually more or less basally connate); 1 adelphous, or 3–12 adelphous (‘polyadelphous’ in Citrus); 1 whorled, or 2 whorled. Androecium exclusively of fertile stamens, or including staminodes. Staminodes (often representing the antepetalous whorl) (3–)4, or 5(–10); external to the fertile stamens. Stamens 2–60; reduced in number relative to the adjacent perianth to polystemonous; alternisepalous, or oppositisepalous (when the outer whorl lost); alternating with the corolla members, or both alternating with and opposite the corolla members. Anthers dorsifixed, or basifixed (more or less, e.g.Erythrochiton, Melicope); versatile; dehiscing via longitudinal slits; introrse (usually), or latrorse (more or less, e.g. Dictamnus); 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 (2 or 3). Tapetum glandular. Pollen grains aperturate; (2–)3–6(–8) aperturate; colporate; 2-celled (in 7 genera), or 3-celled (in 4 genera), or 2-celled and 3-celled (with both states recorded in Ruta).

Gynoecium (1–)3 carpelled (rarely), or 4–5(–100) carpelled (rarely ‘many’, e.g. in Citrus). The pistil when syncarpous, (1–)4–5(–100) celled (to ‘many’). Gynoecium apocarpous to syncarpous; eu-apocarpous, or synstylous, or semicarpous to synovarious (the carpels commonly more or less united basally or at the sides), or synstylovarious to eu-syncarpous (in the Aurantioideae); superior (most commonly), or partly inferior (Platyspermation), or inferior (Aurantioideae). Carpel when apo- or semicarpous, (1–)2–100 ovuled (i.e. to many). Placentation of the free carpels marginal. Ovary when syncarpous, (1–)4–5(–100) locular (i.e. sometimes ‘many’). Styles 1, or 3–5; free, or partially joined; apical. Stigmas wet type, or dry type; papillate, or non-papillate; Group II type, or Group IV type. Placentation when syncarpous, axile. Ovules 1–5(–50) per locule (i.e. to many); pendulous to ascending; epitropous (the micropyle facing upwards, the raphe sometimes branching); always with ventral raphe; when two or more per cell, collateral, or superposed, or biseriate; arillate, or non-arillate; anatropous, or hemianatropous; bitegmic, or unitegmic (rarely); crassinucellate. Outer integument usually contributing to the micropyle, or not contributing to the micropyle (rarely). Embryo-sac development Polygonum-type. Polar nuclei fusing prior to fertilization. Antipodal cells formed; 3; not proliferating; ephemeral. Synergids sometimes hooked (and sometimes with filiform apparatus). Hypostase usually present. Endosperm formation nuclear. Endosperm haustoria present, or absent; chalazal (aggressive, in Aegle). Embryogeny onagrad, or solanad.

Fruit fleshy, or non-fleshy; an aggregate, or not an aggregate. The fruiting carpels coalescing into a secondary syncarp, or not coalescing. The fruiting carpel dehiscent, or indehiscent; when apocarpous, a follicle, or drupaceous, or baccate. Fruit when syncarpous, dehiscent, or indehiscent, or a schizocarp. Mericarps when schizocarpic, 2–5(–100) (?); comprising berrylets, or comprising follicles, or comprising nutlets, or comprising drupelets. Fruit when syncarpous and non-schizocarpic, a berry (often in the form of a hesperidium), or a drupe, or a samara. Seeds endospermic, or non-endospermic. Embryo well differentiated. Cotyledons 2; flat, or folded, or rolled. Embryo chlorophyllous (6/17), or achlorophyllous (3/7); straight, or curved, or bent. Polyembryony recorded (common in Citrus).

Seedling. Germination phanerocotylar, or cryptocotylar.

Physiology, phytochemistry. C3. C3 physiology recorded directly in Citrus, Fortunella, Ruta, Zanthoxylum. Anatomy non-C4 type (Citrus, Haplophyllum). Sugars transported as oligosaccharides + sucrose (in most material sampled), or as sucrose, or as sugar alcohols + oligosaccharides + sucrose. Cyanogenic (rarely), or not cyanogenic. Cynogenic constituents phenylalanine-derived. Alkaloids present (commonly), or absent. Berberine sometimes present (e.g., in Phellodendron). Anthraquinones detected (6 genera); derived from shikimic acid (doubtfully, Clausena), or polyacetate derived (the rest). Arbutin absent. Iridoids not detected. Saponins/sapogenins present (seldom), or absent. Proanthocyanidins present, or absent; when present, cyanidin, or cyanidin and delphinidin. Flavonols present (mostly), or absent (e.g. Eriostemon, Aurantioideae); kaempferol and quercetin, or kaempferol, quercetin, and myricetin. Ellagic acid absent (14 species, 13 genera). Aluminium accumulation not found.

Geography, cytology. Temperate, sub-tropical, and tropical. Pantropical and subtropical, and widespread temperate. X = 7–11(+). Supposed basic chromosome number of family: 9.

Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Rutiflorae; Rutales. Cronquist’s Subclass Rosidae; Sapindales. APG III core angiosperms; core eudicot; Superorder Rosanae; malvid. APG IV Order Sapindales.

Species 900. Genera about 150; Acmadenia, Acradenia, Acronychia, Adenandra, Adiscanthus, Aegle, Aeglopsis, Afraegle, Agathosma, Almeidea, Amyris, Angostura, Apocaulon, Araliopsis, Asterolasia, Atalantia, Balfourodendron, Balsomocitrus, Barosma, Bergera, Boenninghausenia, Boninia, Boronia, Bosistoa, Bouchardatia, Bouzetia, Brombya, Burkillanthus, Calodendrum, Casimiroa, Choisya, Chorilaena, Citropsis, Citrus, Clausena, Clymenia, Cneoridium, Coleonema, Comptonella, Correa, Crowea, Cusparia, Decagonocarpus, Decatropis, Decazyx, Dictamnus, Dictyoloma, Diosma, Diphasia, Diphasiopsis, Diplolaena, Drummondita, Dutaillyea, Empleurum, Eremocitrus, Eriostemon, Erythrochiton, Esenbeckia, Euchaetis, Euodia, Euxylophora, Evodiella, Fagaria, Fagaropsis, Feronia, Feroniella, Fortunella, Galipea, Geijera, Geleznowia, Glycosmis, Halfordia, Haplophyllum, Helietta, Hortia, Ivodea, Kodalyodendron, Leionema, Leptothyrsa, Limnocitrus, Limonia, Lubaria, Lunasia, Luvunga, Maclurodendron, Macrostylis, Medicosma, Megastigma, Melicope, Merope, Merrillia, Metrodorea, Microcitrus, Microcybe, Micromelum, Monanthocitrus, Monnieria, Muiriantha, Murraya, Myrtopsis, Naringi, Naudinia, Nematolepis, Neobyrnesia, Neoraputia, Nycticalanthus, Oricia, Oriciopsis, Orixa, Oxanthera, Pamburus, Paramignya, Peltostigma, Pentaceras, Phebalium, Phellodendron, Philotheca, Phyllosma, Pilocarpus, Pitavia, Platydesma, Pleiospermium, Plethadenia, Polyaster, Poncirus, Pseudiosma, Psilopeganum, Ptelea, Raputia, Raputiarana, Rauia, Raulinosa, Ravenia, Raveniopsis, Rhadinothamnus, Ruta, Rutaneblina, Sarcomelicope, Sargentia, Severinia, Sheilanthera, Sigmatanthus, Skimmia, Spathelia, Spiranthera, Stauranthus, Swinglea, Teclea, Tetractomia, Tetradium, Thamnosma, Ticorea, Toddalia, Toddaliopsis, Tractocopevodia, Triphasia, Vepris, Wenzelia, Zanthoxylum, Zieria, Zieridium.

Economic uses, etc. Many edible fruits from Citrus spp., Aegle, Casimiroa, Clausena etc. (orange, lemon, lime, grapefruit, citron, Bengal quince or bael fruit, casimiroa or white sapote, wampee, etc.); several are or have been officinal (Ruta, Galipea, Toddalia, chiefly on account of their oils).


A lemon
Stuck with cloves
(‘Love’s Labour’s Lost’, v., 2)

The juice, with vinegar, given to smell unto, doth revive and quicken such as have the forgetful sicknesse
(Lyte, of Ruta graveolens)

Illustrations. • Le Maout and Decaisne: Dictamnus, Thamnosma. • Le Maout and Decaisne: Ruta graveolens. • Le Maout and Decaisne: Citrus, Murraya. • Le Maout and Decaisne: Diosma. • Le Maout and Decaisne: (Zanthoxylum). • Toddalia floribunda: Lindley. • Agathosma ciliata: Thonner. • Acronychia pedunculata (as Cyminosma): R. Wight (1840). • Balfourodendron riedelianum, as B. eburneum: Hook. Ic. Pl. 13 (1877–79). • Boronia crenulata: Bot. Reg. XXIV, 12 (1838). • Boronia gunnii: Hooker, Fl. Tasmaniae (1860). • Boronia ledifolia: as B. triphylla var. platifolia, Bot. Reg. 47, 1841. • Boronia serrulata: Bot. Reg. 842, 1825. • Boronia nana: Hook. Ic. Pl. 3 (1840). • Citrus trifoliata: Bot. Mag. 106 (1880). • Correa speciosa var. virens: Bot. Reg. 3, 1815. • Correa reflexa var. speciosa: Bot. Reg. 26, 1815. • Correa alba: Bot. Reg. 515, 1820. • Diplolaena dampieri: Bot. Reg. 64, 1841. • Erythrochiton brasiliensis: Bot. Reg. 29 (47), 1843. • Esenbeckia febrifuga: Martius, Nova Gen. et Spec. Pl. Brasiliensium 3 (1829). • Esenbeckia pilocarpoides subsp. maurioides: Martius, Nova Gen. et Spec. Pl. Brasiliensium 3 (1829). • Galipea odoratissima: Bot. Reg. 1420, 1831. • Helietta parvifolia: Hook. Ic. Pl. 14 (1880–82). • Leionema bilobum ssp. truncatum (as Phebalium): Hooker, Fl. Tasmaniae (1860). • Luvunga scandens: Bot. Mag. 76 (1850). • Micromelum monophyllum: R.Wight (1840). • Ravenia spectabilis: as Lemonia, Bot. Reg. xxvi, 59 (1840).

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.’.