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The families of flowering plants

L. Watson and M.J. Dallwitz

Myrtaceae Juss.

Including Chamaelauciaceae Lindl., Kaniaceae Nakai, Leptospermaceae Kausel, Myrrhinieae (Myrrhiniaceae) Arn.; excluding Heteropyxidaceae, Psiloxylaceae.

Habit and leaf form. Trees and shrubs (including a monotypic mangrove, Osbornia); bearing essential oils; leptocaul. Helophytic to xerophytic. Heterophyllous (sometimes very conspicuously so, depending on maturity of shoots, e.g Eucalyptus spp.), or not heterophyllous. Leaves persistent (nearly always), or deciduous (e.g. some Eucalyptus species); small to large; opposite (commonly), or alternate, or whorled; ‘herbaceous’, or leathery; petiolate, or subsessile, or sessile, or perfoliate; connate (sometimes, e.g. on immature shoots of Eucalyptus), or not connate; gland-dotted; aromatic; borne edgewise to the stem (commonly, comprising the mature foliage Eucalyptus, Callistemon etc.), or borne edgewise to the stem and ‘normally orientated’ (depending on shoot maturity), or ‘normally orientated’; simple; epulvinate. Lamina entire; linear, or lanceolate, or oblong, or ovate; pinnately veined, or parallel-veined, or one-veined. Leaves exstipulate (nearly always), or stipulate (e.g., in Calythrix); leaf development not ‘graminaceous’.

Leaf anatomy. The leaf lamina dorsiventral, or bifacial, or dorsiventral and bifacial (e.g. in Eucalyptus, Eugenia species with both vertical isobilateral leaves and horizontal dorsiventral leaves), or centric. Mucilaginous epidermis present, or absent. Stomata mainly confined to one surface, or on both surfaces (commonly, in edgewise-orientated leaves); anomocytic (usually), or paracytic. Hairs present; exclusively eglandular; sometimes ostensibly multicellular (then 2-chambered), or unicellular (usually). Unicellular hairs branched (sometimes tending to be 2-armed), or simple. Lamina with secretory cavities. Secretory cavities containing oil. Minor leaf veins without phloem transfer cells (6 genera).

Axial (stem, wood) anatomy. Cork cambium present; initially deep-seated, or initially superficial. Nodes ‘typically’ unilacunar. Primary vascular tissues in a cylinder, without separate bundles; very commonly bicollateral. Internal phloem usually present. Secondary thickening developing from a conventional cambial ring. Primary medullary rays wide, or mixed wide and narrow, or narrow.

The wood ring porous to diffuse porous. The vessels small (typically), or medium (less often), or large (rarely); solitary, or radially paired, or in radial multiples, or clustered, or in tangential arcs (but typically exclusively solitary). The vessel end-walls simple (usually), or scalariform. The vessels with vestured pits; with spiral thickening, or without spiral thickening. The axial xylem with tracheids, or without tracheids; commonly with vasicentric tracheids; with fibre tracheids (usually), or without fibre tracheids; with libriform fibres, or without libriform fibres; including septate fibres (rarely, some Eugenia spp.), or without septate fibres. The fibres without spiral thickening. The parenchyma apotracheal, or paratracheal, or apotracheal and paratracheal. The secondary phloem stratified into hard (fibrous) and soft (parenchymatous) zones (usually), or not stratified (e.g. Darwinia, Verticordia). ‘Included’ phloem absent. The wood not storied. Tyloses present (commonly), or absent.

Reproductive type, pollination. Plants hermaphrodite (usually), or polygamomonoecious, or androdioecious (rarely). Pollination entomophilous, or ornithophilous; mechanism conspicuously specialized (Chamelaucium and some relatives, with pollen presentation via a modified part of the style), or unspecialized (mostly).

Inflorescence, floral, fruit and seed morphology. Flowers solitary (rarely), or aggregated in ‘inflorescences’ (usually); when aggregated, in cymes, in spikes, in corymbs, and in panicles, or in heads (the latter notably daisylike in Actinodium). The ultimate inflorescence units usually cymose. Inflorescences terminal, or axillary, or intercalary (conspicuously so in Beaufortia, Callistemon and Melaleuca species); spikes, cymes, corymbs, panicles, even heads; with involucral bracts, or without involucral bracts; not pseudanthial (usually), or pseudanthial (notably in Actinodium, in which the daisy-like, involucrate capitula comprise pink, fertile disc flowers and paler, flattened and sterile ray flowers each with 4 sepals and 4 petals). Flowers often 2 bracteolate; calyptrate (notably in Eucalyptus), or not calyptrate; regular, or somewhat irregular. The floral irregularity (when noticeable) involving the androecium. Flowers cyclic. Free hypanthium present (petals ‘inserted on the calyx’). Hypogynous disk present (lining the hypanthium, when perigynous).

Perianth with distinct calyx and corolla (but these sometimes adnate to one another and constituting an operculum, which is shed at anthesis), or petaline (in Eucalyptus, where the connate ‘petals’ sometimes form the operculum alone), or sepaline (e.g. Osbornia); 4–11; 1 whorled, or 2 whorled; isomerous, or anisomerous. Calyx (3–)4–5(–6) (or vestigial); 1 whorled; polysepalous, or gamosepalous (then sometimes splitting irregularly at anthesis, or shed entire); regular; calyptrate, or not calyptrate; imbricate (usually quincuncial), or valvate (or splitting irregularly). Corolla 4–5; 1 whorled; polypetalous (the petals often almost circular when flattened), or gamopetalous; calyptrate, or not calyptrate; imbricate; regular; white, or yellow, or red, or pink, or purple (not blue).

Androecium 4–5 (rarely), or 8–10 (sometimes), or 20–150 (i.e., usually ‘many’). Androecial members branched, or unbranched; when ‘many’, maturing centripetally; free of the perianth; all equal, or markedly unequal; free of one another, or coherent; when united, 1 adelphous (connate into a short tube), or 4–5 adelphous; when ‘definite’, 2 whorled. The androecial bundles when bundled, alternating with the corolla members, or opposite the corolla members. Androecium exclusively of fertile stamens, or including staminodes (sometimes, when A indefinite). Stamens (4–)10–150; isomerous with the perianth (rarely), or diplostemonous (sometimes), or triplostemonous to polystemonous (usually); erect in bud, or inflexed in bud (or twice folded). Filaments appendiculate (those of Corynanthera having a stipitate appendage around the level of the anther, perhaps representing the fourth sporangium of the trisporangiate anther), or not appendiculate (usually). Anthers dorsifixed; versatile; dehiscing via longitudinal slits, or dehiscing via pores (rarely); introrse; bilocular (mostly), or unilocular (e.g. Corynanthera); mostly tetrasporangiate (but trisporangiate in Corynanthera, and occasionally unisporangiate in Malleostemon); appendaged (often tipped by a gland), or unappendaged. Endothecium developing fibrous thickenings. Anther epidermis degenerating. Anther wall initially with one middle layer, or initially with more than one middle layer (1 or 2). Tapetum glandular. Pollen grains aperturate; (2–)3(–4) aperturate; colpate (seldom), or colporate (commonly), or porate (sometimes syncolpate); 2-celled (in 6 genera).

Gynoecium 2–5(–16) carpelled. The pistil (1–)2–5(–16) celled. Gynoecium syncarpous; synstylovarious to eu-syncarpous; inferior (usually, more or less), or partly inferior (to varying degrees, rarely ‘almost superior’). Ovary (1–)2–5(–16) locular. Epigynous disk present, or absent (when perigynous). Gynoecium stylate. Styles 1; apical. Stigmas 1. Placentation when unilocular, parietal (on intrusive placentas, e.g. Feijoa); axile. Ovules in the single cavity 30–150 (‘many’); 2–50 per locule (i.e. to ‘many’); ascending; non-arillate; hemianatropous to anatropous; usually bitegmic; crassinucellate. Outer integument contributing to the micropyle, or not contributing to the micropyle. Embryo-sac development Polygonum-type. Polar nuclei fusing prior to fertilization (usually), or fusing only after one has been fertilized (e.g. in Myrtus, Syzygium). Antipodal cells formed, or not formed (then the three nuclei degenerating early); when formed, 3; not proliferating; very ephemeral. Synergids pear-shaped, or hooked (commonly, and sometimes with filiform apparatus). Endosperm formation nuclear. Embryogeny onagrad (or adventive).

Fruit fleshy, or non-fleshy; dehiscent, or indehiscent; a capsule, or a berry, or a drupe, or a nut. Capsules septicidal, or loculicidal, or denticidal, or circumscissile (then becoming operculate by removal of the epigynous disk). Seeds non-endospermic; winged (e.g. in some Eucalyptus), or wingless. Cotyledons 2. Embryo chlorophyllous (3 Eugenia species), or achlorophyllous (4/4); straight, or bent, or other than straight, curved, bent or coiled (sometimes spiral). Polyembryony commonly recorded.

Seedling. Germination phanerocotylar, or cryptocotylar.

Physiology, phytochemistry. C3. C3 physiology recorded directly in Eucalyptus, Metrosideros. Anatomy non-C4 type (Eugenia, Leptospermum, Psidium). Sugars transported as sucrose (in Syzygium), or as oligosaccharides + sucrose (mostly), or as sugar alcohols + oligosaccharides + sucrose (occasionally). Inulin recorded (Eucalyptus, Gibbs 1974). Cyanogenic, or not cyanogenic (usually). Cynogenic constituents phenylalanine-derived. Alkaloids present (rarely), or absent. Iridoids not detected. Saponins/sapogenins present, or absent (mostly). Proanthocyanidins present; cyanidin and delphinidin (usually), or cyanidin. Flavonols present; kaempferol, or kaempferol and quercetin, or quercetin and myricetin, or kaempferol, quercetin, and myricetin. Ellagic acid present (9 species, 7 genera), or absent (4 species, 4 genera). Ursolic acid present. Aluminium accumulation not found.

Geography, cytology. Temperate, sub-tropical, and tropical. Widespread warm, chiefly centred in Australia and tropical America. X = (6-)11(-12).

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 3000. Genera about 130; Acca, Accara, Acmena, Acmenosperma, Actinodium, Agonis, Allosyncarpia, Amomyrtella, Amomyrtus, Angasomyrtus, Angasomyrtus, Angophora, Aphanomyrtus, Archirhodomyrtus, Arillastrum, Astartea, Asteromyrtus, Austromyrtus, Backhousia, Baeckea, Balaustion, Barongia, Basisperma, Beaufortia, Blepharocalyx, Callistemon, Calothamnus, Calycolpus, Calycorectes, Calyptranthes, Calyptrogenia, Calytrix, Campomanesia, Carpolepis, Chamelaucium, Chamguava, Choricarpia, Cleistocalyx, Cloezia, Conothamnus, Corynanthera, Corynemyrtus, Cupheanthus, Darwinia, Decaspermum, Eremaea, Eucalyptopsis, Eucalyptus, Eugenia, Gomidesia, Feijoa (=Acca), Heteropyxis, Hexachlamys, Homalocalyx, Homalospermum, Homoranthus, Hottea, Hypocalymma, Jambosa, Kania, Kjellbergiodendron, Kunzea, Lamarchea, Legrandia, Lencymmoea, Leptospermum, Lindsayomyrtus, Lophomyrtus, Lophostemon, Luma, Lysicarpus, Malleostemon, Marlieria, Melaleuca, Meteoromyrtus, Metrosideros, Micromyrtus, Mitranthes, Mitrantia, Monimiastrum, Mosiera, Mozartia, Myrceugenia, Myrcia, Myrcianthes, Myrciaria, Myrrhinium, Myrtastrum, Myrtella, Myrteola, Myrtus, Neofabricia, Neomitranthes, Neomyrtus, Ochrosperma, Octamyrtus, Osbornia, Paramyrciaria, Pericalymma, Phymatocarpus, Pileanthus, Pilidiostigma, Piliocalyx, Pimenta, Pleurocalyptus, Plinia, Pseudanamomis, Pseudeugenia, Psidium, Purpureostemon, Pyrenocarpa, Regelia, Rhodamnia, Rhodomyrtus, Rinzia, Ristantia, Rylstonea, Scholtzia, Siphoneugenia, Sphaerantia, Stereocaryum, Syncarpia, Syzygium, Tepualia, Thryptomene, Tristania, Tristaniopsis, Ugni, Uromyrtus, Verticordia, Waterhousea, Welchiodendron, Whiteodendron, Xanthomyrtus, Xanthostemon.

Economic uses, etc. Many sources of essential oils for perfumery and medicine, and edible fruits from (e.g.) Feijoa (Brazilian guava, etc.), Eugenia spp. (jambos, rose-apple, pitanga etc.), Campomanesia (guabiroba).


Once a jolly swagman camped by a billabong,
Under the shade of a Coolabah tree
(A.B. Paterson, ‘Waltzing Matilda’ - Eucalyptus microtheca)

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

Illustrations. • Le Maout and Decaisne: Beaufortia, Myrtus. • Eugenia natalitia: Thonner. • Le Maout and Decaisne: Calycothrix (= Calythrix), Caryophyllus (= Syzygium), Eucalyptus, Fabricia (= Leptospermum). • Actinodium cunninghamii: 'Albany daisy', capitula (photo). • Actinodium cunninghamii: habitat (photo). • Agonis flexuosa: flowers (photo). • Agonis fexuosa: coastal habitat (photo). • Baeckea leptocaulis: Hook. Ic. Pl. 3 (1840). • Baeckea camphorosmae: as Babingtonia, Bot. Reg. 10 1842. • Balaustion pulcherrimum: Hook. Ic. Pl. 9 (1852). • Beaufortia decussata: Bot. Reg. 18, 1815. • Callistemon citrinus: Bot. Mag. 260 (1794). • Callistemon citrinus: Bot. Mag. 260 (1794), text. • Callistemon rigidus: Bot. Reg. 393, 1819. • Calothamnus villosus: Bot. Reg. 1099, 1827. • Calytrix tetragona: Bot. Reg. 409, 1819. • Corymbia maculata, as Eucalyptus: Hook. Ic. Pl. 7–8 (1844). • Leptospermum recurvum: Hook. Ic. Pl. 9 (1852). • Leptospermum rupestre: Hooker, Fl. Tasmaniae (1860). • Lophostemon confertus: as Tristania macrophylla, Bot. Reg 1839 (1836). • Eucalyptus risdonii: Hooker, Fl. Tasmaniae (1860). • Eucalyptus coccifera: Hooker, Fl. Tasmaniae (1860). • Eucalyptus urnigera: Hooker, Fl. Tasmaniae (1860). • Eucalyptus gunnii: Hooker, Fl. Tasmaniae (1860). • Eucalyptus gigantea, cf. delegatensis ssp. tasmaniensis: Hooker, Fl. Tasmaniae (1860). • Eugenia lucida: Trimen, Ill. Fl. Ceylon (1894). • Leptospermum rupestre: Hook. Ic. Pl. 4 (1841). • Lysicarpus angustifolius, as L. ternifolius: Hook. Ic. Pl. 11 (1867–71). • Melaleuca fulgens: Bot. Reg. 103, 1816. • Melaleuca incana: Bot. Reg. 410, 1819. • Melaleuca squamea: Bot. Reg. 477, 1820. • Metrosideros florida (cf. fulgens): Hooker, Fl. Novae-Zelandiae (1853). • Metrosideros diffusa (as hypericifolia): Hooker, Fl. Novae-Zelandiae (1853). • Metrosideros robusta: Hooker, Fl. Novae-Zelandiae (1853). • Myrrhinium atropurpureum: Martius, Nova Gen. et Spec. Pl. Brasiliensium 3 (1829). • Osbornia octodonta: Hook. Ic. Pl. 11 (1867–71). • Rhodomyrtus macrocarpa: Hook. Ic. Pl. 11 (1867–71). • Rhodomyrtus tomentosa: Bot. Mag. 250, 1794. • Syzygium brackenridgei, as Paraeugenia imthurnii: Hook. Ic. Pl. 31 (1915). • Syzygium fergusonii, as Eugenia: Trimen, Ill. Fl. Ceylon (1894). • Verticordia roei: Hook. Ic. Pl. 28 (1905). • Xanthostemon chrysanthus: Hook. Ic. Pl. 11 (1867–71).

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.’.