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Eucalyptus articulata



Eucalyptus articulata Brooker & Hopper, Nuytsia 9: 14 (1993).

T: 22 km E of Mulga Rock, Great Victoria Desert, 30
°09'S, 123°17'E, 25 June 1987, M.I.H.Brooker 9686 & S.D.Hopper; holo: PERTH; iso: AD, CANB, MEL, NSW.

Mallee to 3 m tall. Forming a lignotuber.
Bark smooth throughout, coppery or bronze.
Branchlets with oil glands in the pith.
Juvenile growth (coppice or field seedlings to 50 cm): stems rounded in cross-section; juvenile leaves always petiolate, opposite for few nodes then alternate, broadly lanceolate, 6-12 cm long, 1-1.5 cm wide, dull, blue-green (non-glaucous).
Adult leaves alternate, petioles 0.8-1.8 cm long
; blade lanceolate, 6-12 cm long, 1-1.5 cm wide, base tapering to petiole, margin entire, apex acute, concolorous, glossy, dark green, side veins acute, reticulation sparse to moderate, intramarginal vein remote from margin, oil glands numerous, island, irregular.
Inflorescences axillary unbranched, or at times apparently terminal due to loss of apical vegetative bud, peduncles flattened, 0.5-1.5 cm long; buds 7, stoutly pedicellate, obovoid to pyriform, scar present, operculum rounded and sometimes apiculate or bluntly conical, stamens inflexed with their filaments geniculate, anthers cuboid, versatile, sub-basifixed, dehiscing by longitudinal slits, style long and straight, the base tapering and articulate in a pit in the ovary roof, stigma blunt to rounded, locules 3 or 4, the placentae each with 4 vertical rows of ovules; flowers white.
Fruit pedicellate, obconical or at times almost cylindrical, 0.4-0.6 cm wide, disc descending vertically, valves 3 or 4, enclosed to near rim level.
Seed brown, 0.7-1.5 mm long, ovoid to flattened-ovoid or cuboid but scarcely angular, dorsal surface shallowly reticulate, hilum ventral.

Cultivated seedling (measured at ca node 10): cotyledons Y-shaped (bisected); stems rounded in cross-section; leaves always petiolate, opposite for 3 to 6 nodes, lanceolate, 5-10 cm long, 1.2-3 cm wide, green, slightly glossy.


NOTES

Eucalyptus articulata (Latin, articulatus, articulate or jointed, referring to the style base).

A low straggly mallee endemic to Western Australia, known only from near Mulga Rock, north-east of Kalgoorlie, where it occurs on red sand dunes with arkose rubble. The bark is smooth, bright coppery in season, and the adult leaves are very glossy green with sparse venation and conspicuous oil glands.

Eucalyptus articulata belongs to Eucalyptus subgenus Symphyomyrtus section Bisectae subsection Glandulosae because the cotyledons are bisected, buds have an operculum scar and the branchlets have oil glands in the pith. Within this subsection E. articulata belongs to a small subgroup of four species, series Loxophlebae, further characterized by having buds with fully inflexed stamens with the filaments geniculate or strongly elbowed and a style that tapers basally, sparsely reticulate glossy green adult leaves and small obconical fruit. The four species are E. loxophleba (with 4 subspecies), E. blaxellii , E. articulata and from north-east of Meekatharra (beyond the scope of this edition of EUCLID) E. semota.

Eucalyptus articulata is unlikely to be confused with any other species within its natural range. Its geographically closest relative is the smooth-barked E. loxophleba subsp. lissophloia which is distinguished from E. articulata by having glaucous branchlets and glaucous, more or less deltoid, juvenile leaves. E. articulata has blue-green (non-glaucous) lanceolate juvenile leaves and non-glaucous branchlets. The style base of E. articulata is articulate where it is inserted in a pit in the ovary roof, a character absent from E. loxophleba , but present also in E. semota and E. blaxellii.