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Eucalyptus arenacea


Desert stringybark

Eucalyptus arenacea Marginson & P.Ladiges, Austral. Syst. Bot. 1: 163 (1988).

T: Big Desert, Victoria, 24 km N of Yanac on road to Murrayville, 4 July 1981, J.C. Marginson 224: holo: MEL; iso: MELU,CANB,NSW,AD.


Mallee or small tree to 10 m tall. Forming a lignotuber.
Bark rough to small branches in trees, stringy, grey or brown; in mallees shortly fibrous to flaky on stems with branches smooth.
Juvenile growth (coppice or field seedlings to 50 cm): stem rounded in cross-section, scabrid at first, becoming smooth; juvenile leaves opposite and sessile for a few pairs, scabrid above and below, becoming alternate, petiolate, ovate, 3.5-8.5 cm long, 3-4 cm wide, margin entire, becoming smooth, green and glossy.
Adult leaves alternate, petiole 1-2.5 cm long; blade broadly lanceolate to lanceolate to falcate, 7-12 cm long, 1.5-4 cm wide, base oblique or tapering to petiole, margin entire, concolorous, glossy, green, side-veins at an acute or wider angle to midrib, sparsely reticulate, intramarginal vein parallel to and well removed from margin, oil glands island or obscure.
Inflorescences axillary unbranched, peduncles 0.7-1.8 cm long; buds 9 to 15, pedicellate, clavate to ovoid, green to yellow, smooth or scurfy, scar absent, operculum conical to rounded, stamens irregularly flexed, anthers reniform to cordate, versatile, dorsifixed, dehiscing by (usually) confluent slits, style long, locules 3 or 4, the placentae each with 2 vertical ovule rows; flowers white.
Fruit sessile or shortly pedicellate, hemispherical or truncate-globose, 0.7-1 cm wide, disc raised or level, valves 3 or 4, slightly exserted or near rim level.
Seed brown to reddish brown, 1.8-3 mm long, pyramidal or obliquely pyramidal, dorsal surface smooth or very slightly pitted, hilum terminal.

Cultivated seedlings (measured at ca node 10): cotyledons reniform; stems rounded in cross-section, stellate-hairy; leaves sessile for ca 8 to 10 nodes, opposite for ca 5 to 6 nodes then alternate, lower leaves elliptic but by node ca 6 becoming ovate, 3-8.5 cm long, 1.5-4 cm wide, base amplexicaul becoming rounded to tapering at upper nodes, discolorous, bright green above, stellate-hairy.


NOTES

Eucalyptus arenacea (Latin arenaceus, sandy, of the habitat).

A stringybark common in mallee areas of the upper south-east of South Australia and the Little Desert and Big Desert of western Victoria. Occurrence on Kangaroo Island is doubtful and the mallees attributed to it may be better classified as E. baxteri .

E. arenacea is related to E. baxteri from which it differs in the lower stature, smoother (not or scarcely warty) buds that are pedicellate, and by the flatter disc of the fruit. It grows on very poor soils including white sands.

Eucalyptus arenacea belongs to Eucalyptus subgenus Eucalyptus section Capillulus series Pachyphloius (the stringybarks), being trees with coarsely fibrous, stringy bark, shortly emergent oil glands with obvious radiating hairs on stems and lower leaves of seedlings and juvenile growth, axillary inflorescences with buds having only one operculum and reniform anthers
, ovules are in 2 rows, and ± pyramidal seeds.

In general many stringybarks are difficult to identify to species with certainty. In this edition of EUCLID we recognize 26 species in southern Australia. The stringybarks can be divided into 5 groups as follows -

1. Buds pedicellate, clavate - E. muelleriana , E. laevopinea .

2. Buds pedicellate, operculum beaked - E. macrorhyncha subsp. macrorhyncha and E. macrorhyncha subsp. cannonii.

3. Buds more or less sessile, angular longitudinally - E. mackintii , E. williamsiana , E. boliviana , E. youmanii , E. capitellata , E. camfieldii , E. bensonii.

4. Buds with tapering pedicels or sessile, fusiform to narrowly ovoid - E. cameronii , E. globoidea , E. caliginosa , E. eugenioides , E. sparsifolia , E. tenella , E. mckieana , E. ligustrina , E. tindaliae , E. agglomerata.

5. Buds more or less sessile, opercula flat to obtuse or rarely acute - E. baxteri , E. blaxlandii , E. imitans , E. verrucata , E. serraensis .

Eucalyptus arenacea is a somewhat anomolous stringybark as its buds are pedicellate and more or less clavate, and on the above criteria, may be placed in group 1 but it is widely regarded as being close to E. baxteri of group 5,
on the similarity of fruit and coarseness of seedling leaves.