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Eucalyptus L'Her.
Sert.Angl. (1789)

Scientific Description
H.R. Coleman, Thursday 8 September 2016

Common name. Eucalypts. Family Myrtaceae.

Habit and leaf form. Trees, or shrubs; evergreen; non-laticiferous and without coloured juice; bearing essential oils. ‘Normal’ plants. Leaves well developed. Plants non-succulent; autotrophic. Young stems not breaking easily at the nodes. To 2–36.74–100 m high. Self supporting. Stem growth not conspicuously sympodial. Leptocaul. Helophytic, or mesophytic, or xerophytic. Heterophyllous. Leaves small, or medium-sized, or large; alternate, or opposite; with blades; ‘herbaceous’, or leathery; petiolate, or sessile; connate, or not connate; gland-dotted, or not gland-dotted; aromatic; edgewise to the stem, or with ‘normal’ orientation; simple; not peltate; epulvinate. Leaf blades neither inverted nor twisted through 90 degrees; dorsiventral, or isobilateral; entire; not conspicuously asymmetric; flat; linear, or lanceolate, or ovate, or oblong; ovate, or oblong, or elliptic, or orbicular; one-veined, or pinnately veined, or parallel-veined; cross-venulate. Leaves eligulate; without stipules; without a persistent basal meristem. Vernation not circinnate. Leaf anatomy. Leaf blade epidermis without differentiation into ‘long’ and ‘short’ cells. Guard-cells not ‘grass type’. Urticating hairs absent. Stem anatomy. Secondary thickening developing from a conventional cambial ring. Xylem vessels solitary. Paratracheal parenchyma scanty. Roots. Roots without velamen.

Reproductive type, pollination. Fertile flowers hermaphrodite. Unisexual flowers absent. Plants hermaphrodite. Entomophilous, or ornithophilous. Pollination mechanism unspecialized.

Inflorescence and flower features. Flowers aggregated in ‘inflorescences’; in umbels. Inflorescences simple, or compound. Flowers not in ‘spikelets’. The terminal inflorescence unit cymose. Inflorescences not scapiflorous; terminal, or axillary; without involucral bracts; not pseudanthial; espatheate. The fruiting inflorescence not conelike. Flowers pedicellate, or sessile; bracteolate, or ebracteolate; small, or medium-sized, or large; operculate (calyptrate); regular; not resupinate; neither papilionaceous or pseudo-papilionaceous; 4 merous; cyclic. Floral receptacle with neither androphore nor gynophore. Free hypanthium present; campanulate, or obconic, or turbinate, or urceolate, or tubular. Perianth with distinct calyx and corolla; 8, or 10; 2 -whorled; isomerous; without spots. Calyx present; 4, or 5; not represented by bristles; 1 -whorled; polysepalous, or gamosepalous; entire; calyptrate, or not calyptrate; shed before the corolla, or not shed before the corolla; imbricate, or valvate; regular; neither appendaged nor spurred; persistent, or not persistent. Epicalyx absent. Corolla present; 4, or 5; 1 -whorled; alternating with the calyx; not appendiculate; polypetalous, or gamopetalous; entire. Corolla tube not noticeably adaxially split. Corolla calyptrate; integrally fused-calyptrate, or not integrally fused-calyptrate; imbricate; regular; not spurred; not fleshy. Fertile stamens present. Androecial members indefinite in number. Androecium 20–85–150. Androecial members branched. Androecial sequence determinable, or not determinable. Androecial members maturing centripetally; free of the perianth; free of the gynoecium; all equal, or markedly unequal; free of one another, or coherent; when coherent, 4 - adelphous. The androecial groups opposite the sepals, or opposite the petals. Androecium exclusively of fertile stamens, or including staminodes. Staminodes non-petaloid. Stamens 20–85–150; not didynamous, not tetradynamous; polystemonous; erect in bud, or inflexed in bud; filantherous. Filaments not appendiculate. Anthers separate from one another; dorsifixed, or basifixed; not becoming inverted during development; versatile, or non-versatile; dehiscing via pores, or dehiscing via longitudinal slits; introrse; tetrasporangiate; appendaged, or unappendaged. The anther appendages dorsal. Pollen shed as single grains. Pollen grains not dispersed as long filaments. Fertile gynoecium present. Gynoecium 2 carpelled, or 3 carpelled, or 4 carpelled, or 5 carpelled, or 6–7 carpelled. The pistil 2 celled, or 3 celled, or 4 celled, or 5 celled, or 6–7 celled. Gynoecium non-petaloid. Carpels reduced in number relative to the perianth, or isomerous with the perianth. Gynoecium syncarpous; eu-syncarpous; inferior. Ovary plurilocular; 2 locular, or 3 locular, or 4 locular, or 5 locular, or 6–7 locular. Locules without ‘false septa’; not horizontally divided. Epigynous disk present. Gynoecium stylate. Styles 1; without an indusium; apical. Styles straight in bud, or bent in bud. Stigmas 1; dorsal to the carpels. Placentation axile. Ovules 20–50 per locule; ascending; non-arillate; hemianatropous, or anatropous.

Fruit and seed features. Fruit aerial; sessile; non-fleshy; not an aggregate; dehiscent; a capsule. Gynoecia of adjoining flowers not forming a multiple fruit. Raphe of hemitropous type absent, or present. Raphe of anatropous type absent, or present. Seeds non-endospermic. Perisperm absent. Seeds not conspicuously hairy; with a testa; winged, or wingless. Seed wings not encircling body. Embryo well differentiated. Cotyledons 2; folded; reniform, or bilobed, or bisected. Testa not cracking; smooth; without phytomelan; with a crystalliferous layer, or without a crystalliferous layer. Micropyle not zigzag.

Special features. The funicles not as in Acanthaceae. Non-mangrove species. Juvenile leaves all petiolate, or sessile or subsessile at some stage. Leaves never tightly cordate, subpeltate or peltate. Adult leaves with many lateral veins; with an intramarginal vein distinct from the thickened margin, or with no distinct intramarginal vein. Oil glands without radiating hairs, or with radiating thin-walled blunt-ended hairs. Protuberant oil glands with 4 cap cells, or with 2 cap cells. Oil-gland cap cells smooth. Thin-walled blunted-ended hairs present, or absent. Hairs uniseriately multicellular. Bristle-glands absent. Pith of leafy twigs without large oil ducts. Inflorescence phyllotaxy fixed opposite. Corolla completely congenitally fused with the calyx, or not congenitally fused with the calyx. Stigmatic papillae long, or short. Ovules in vertical rows. Ovules in 2 rows, or 3 rows, or 4 rows, or 5 rows, or 6 rows, or 7–10 rows. Inner integument not resorbed in seed, or resorbed in seed. Outer integument 4 cells thick, or 2 cells thick. Not hosting Glycaspis subgenus Glycaspis, or hosting psyllids from the genus Glycaspis subgenus Glycaspis. Gynoecium and fruit not as in Resedaceae.

Geography, cytology, number of species. Native of Australia. Endemic to Australia, or not endemic to Australia. Australian states and territories: Western Australia, or South Australia, or Northern Territory, or Queensland, or New South Wales, or Victoria, or Australian Capital Territory, or Tasmania. Northern Botanical Province, or Eremaean Botanical Province, or South-West Botanical Province.

Etymology. From the Greek for "well" and "covered"; refers to the operculum or cap which covers the stamens in bud.

Taxonomic Literature

• Nicolle, Dean; French, Malcolm E. (2012). Two new mallee box species (Eucalyptus sect. Adnataria ser. Lucasianae: Myrtaceae) from the Pilbara region of Western Australia.
• Nicolle, Dean; French, Malcolm; McQuoid, Nathan (2008). A revision of Eucalyptus ser. Cornutae subser. Conjunctae (Myrtaceae) from the south coast of Western Australia, including the description of four new taxa and comments on the hybrid origin of E. bennettiae.
• Nicolle, Dean; Brooker, Ian (2008). An updated diagnosis for Eucalyptus series Accedentes (Myrtaceae) and a new mallee species for the series occurring in far western Australia.
• Hopper, Stephen D.; Nicolle, Dean (2007). Diamond gum (Eucalyptus rhomboidea: Myrtaceae), a new threatened species endemic to the Bremer Range of the southwest Australian floristic region.
• Nicolle, Dean; French, Malcolm E. (2007). A new geographically disjunct and apparently rare subspecies of Eucalyptus jutsonii (Myrtaceae) from Western Australia.
• Nicolle, D.; Brooker, M. I. H. (2005). Re-assessment of the saline-dwelling Eucalyptus spathulata complex (Myrtaceae) from southern Western Australia.
• Nicolle, Dean (2005). A rare and endangered new subspecies of Eucalyptus sargentii (Myrtaceae) with high potential for revegetation of saline sites from south-western Australia and notes on E. diminuta and E. sargentii subsp. fallens.
• Brooker, M. I. H.; Hopper, S. D. (2002). Taxonomy of species deriving from the publication of Eucalyptus subseries Cornutae (Myrtaceae).
• McQuoid, N. K.; Hopper, S. D. (2002). Eucalyptus calyerup (Myrtaceae), a new species of possible hybrid origin from south-western Australia.
• Nicolle, D. (2002). A revision of Eucalyptus series Calcicolae (Myrtaceae) from the south coast of Western Australia.
• Nicolle, D. (2002). Two new species of silver mallet (Eucalyptus: Myrtaceae) of very restricted distribution in south-western Western Australia.
• Wheeler, Judy; Marchant, Neville; Lewington, Margaret; Graham, Lorraine (2002). Flora of the south west, Bunbury, Augusta, Denmark. Volume 2, dicotyledons. Australian Biological Resources Study. Canberra.
• Hill, K. D.; Johnson, L. A. S.; Blaxell, D. F. (2001). Systematic studies in the eucalypts. 11, new taxa and combinations in Eucalyptus section Dumaria (Myrtaceae).
• Nicolle, Dean (2001). Notes on Eucalyptus series Orbifoliae (Myrtaceae) including a new species from central Australia.
• Nicolle, Dean (2000). A review of the Eucalyptus calycogona group (Myrtaceae) including the description of three new taxa from southern Australia.
• Nicolle, Dean (2000). Three new taxa of Eucalyptus subgenus Eudesmia (Myrtaceae) from Queensland and Western Australia.
• Johnson, L. A. S.; Hill, K. D.; National Herbarium of New South Wales (1999). Systematic studies in the eucalypts. 9, a review of series Sociales (Eucalyptus subgenus Symphyomyrtus, section Bisectaria: Myrtaceae).
• Hill, K. D.; Johnson, L. A. S. (1998). Systematic studies in the eucalypts. 8, a review of the eudesmioid eucalypts, Eucalyptus subgenus Eudesmia (Myrtaceae).
• French, Malcolm E. (1997). The special eucalypts of Perth and the south west. F&N Publications. [Carine, W.A.].
• Nicolle, Dean (1997). A taxonomic revision of the Eucalyptus striaticalyx group (Eucalyptus series Rufispermae: Myrtaceae).
• Brooker, M. I. H.; Slee, A. V. (1996). New taxa and some new nomenclature in Eucalyptus.
• Macpherson, C. J.; Grayling, P. M. (1996). Eucalyptus semota (Myrtaceae), a new species from the Ashburton District of Western Australia.
• Bennett, E. M. (1995). Hybrid between Eucalyptus tetraptera and Eucalyptus stoatei from Jerdacuttup, Western Australia.
• Brooker, M. I. H.; Slee, A. V. (1995). Eucalyptus series Preissianae (Myrtaceae), a new series of Western Australian eucalypts and the description of a new subspecies in the series.
• Brooker, M. I. H.; Slee, A. V. (1994). Eucalyptus series Brevifoliae (Myrtaceae), a new series of northern Australian eucalypts.
• Brooker, M. I. H.; Kleinig, D. A. (1994). Field guide to eucalypts : northern Australia. Inkata. Sydney.
• Hill, K. D.; Johnson, L. A. S. (1994). Systematic studies in the eucalypts. 6, a revision of the coolibahs, Eucalyptus subgenus Symphyomyrtus section Adnataria series Oliganthae subseries Microthecosae (Myrtaceae).
• Brooker, M. I. H.; Hopper, S. D. (1993). New series, subseries, species and subspecies of Eucalyptus (Myrtaceae) from Western Australia and from South Australia.
• Dunlop, C. R.; Done, C. C. (1992). Eucalyptus ordiana (Myrtaceae), a new species from the Kimberley, Western Australia.
• Grayling, P. M.; Brooker, M. I. H. (1992). Four new species of Eucalyptus (Myrtaceae) from Western Australia.
• Hill, K. D.; Johnson, L. A. S.; National Herbarium of New South Wales (1992). Systematic studies in the eucalypts. 5, new taxa and combinations in Eucalyptus (Myrtaceae) in Western Australia.
• Leighton, Pattie; Moir, Penny; Burch, Louise (1992). Eucalypts of the Wellstead District. [Wellstead Historical & Heritage Committee]. [Wellstead, W.A.].
• Brooker, M. I. H.; Hopper, Stephen D. (1991). A taxonomic revision of Eucalyptus wandoo, E. redunca and allied species (Eucalyptus series Levispermae Maiden: Myrtaceae) in Western Australia.
• Brooker, M. I. H.; Kleinig, D. A. (1990). Field guide to eucalypts. Volume 2, south-western and southern Australia. Inkata. Melbourne.
• Brooker, M. I. H.; Hopper, S. D. (1989). A new series, Rigentes, of Eucalyptus (Myrtaceae) comprising three new species endemic to Western Australia.
• Brooker, M. I. H. (1988). Eucalyptus foecunda revisited and six related new species (Myrtaceae).
• Brooker, M. I. H.; Done, C. C. (1986). Eucalyptus ceracea, E. rupestris and E. chlorophylla (Myrtaceae), three new species in the Kimberley Division of Western Australia.
• Brooker, M. I. H.; Edgecombe, W. B. (1986). Eucalyptus ferritcola and E. pilbarensis (Myrtaceae), two new species from the Pilbara region of Western Australia.
• Brooker, M. I. H. (1986). New species and subspecies of the informal Eucalyptus series Calycogonae Pryor & Johnson (Eucalyptus series Aridae Blakely: Myrtaceae).
• Brooker, M. I. H.; Hopper, S. D. (1986). Notes on the informal subgenus Monocalyptus of Eucalyptus (Myrtaceae) and the description of three new upland species from south-west Western Australia.
• Crisp, M. D. (1984). Eucalyptus ornata (Myrtaceae), a new silver mallet from near Kondinin, Western Australia.
• Carr, D. J.; Carr, S. G. M. (1983). Eucalyptus petraea sp. nov. and E. lucasii (Myrtaceae) : two Western Australian boxes.
• Brooker, M. I. H.; Hopper, S. D. (1982). New subspecies in Eucalyptus caesia and in E. crucis (Myrtaceae) of Western Australia.
• Crisp, M. D. (1982). Eucalyptus synandra (Myrtaceae), a new species of mallee from Western Australia.
• Carr, D. J.; Carr, S. G. M. (1980). The Lehmannianae : a natural group of Western Australian eucalypts.
• Brooker, M. I. H.; Blaxell, D. F. (1978). Five new species of Eucalyptus from Western Australia.
• Brooker, M. I. H. (1976). Six new taxa of Eucalyptus from Western Australia.
• Brooker, M. I. H. (1974). Eucalyptus forrestiana subsp. dolichorhyncha, a new taxon from Western Australia.
• Brooker, M. I. H. (1974). Six new species of Eucalyptus from Western Australia.
• Brooker, M. I. H. (1972). Four new taxa of Eucalyptus from Western Australia.