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Eucalyptus arachnaea subsp. arrecta Brooker & Hopper, Nuytsia 8:70 (1991).
T: west of Morawa, 29°08'S,
115°44'E,
Western Australia, 3 Feb. 1988, M.I.H.Brooker 9879 & C.Sounness;
holo: PERTH; iso: AD, CANB, MEL, NSW.
Tree (mallet) to 10 m tall. Lignotuber absent.
Bark rough, grey-black for up to 2-3 m of trunk, tightly fibrous
and fissured to flaky, smooth above, grey and yellowish brown.
Branchlets with pith oil glands at the nodes.
Juvenile growth (coppice or field seedlings to 50 cm):
not seen.
Adult leaves alternate, petioles 0.8-2 cm long; blade lanceolate,
6-12 cm long, 1-2.2 cm wide, base tapering to petiole, margin entire,
apex pointed, concolorous, very glossy, green, side veins at an acute
or wider angle to midrib, reticulation moderate to dense, intramarginal
vein remote from margin, oil glands mostly island.
Inflorescences axillary unbranched, peduncles widening apically,
0.8-1.8 cm long; buds ?9 or 11, pedicellate, elongated-fusiform, scar
present, operculum horn-shaped, three to four times the length of
the hypanthium and narrower than it at the join, a few outer stamens
erect, most stamens variably deflexed, anthers oblong, versatile,
dorsifixed, dehiscing by longitudinal slits, style long and straight,
stigma more or less tapered, locules 3, the placentae each with 4
vertical rows of ovules; flowers creamy white.
Fruit pedicellate, cylindrical to obconical or cupular, 0.4-0.5
cm wide, disc descending vertically, valves 3, near rim level or tips
scarcely exserted.
Seed straw-coloured, 0.5-1.2 mm, sub-spherical, surface smooth,
hilum ventral/terminal.
Cultivated seedling (measured at ca node 10): cotyledons Y-shaped
(bisected); stems more or less square in cross-section, very warty;
leaves always petiolate, opposite for 2 to 4 nodes then alternate,
broadly lanceolate to ovate, 8-10.5 cm long, 2.5-4 cm wide, new tip
growth slightly glaucous but expanded leaves blue-green to green,
slightly glossy by node 10; margin of leaf irregular due to warts
which can also be found on petiole and scattered on leaf surfaces.
NOTES
Eucalyptus arachnaea
(Latin, arachnaeus, spidery, referring to the bud clusters).
A mallee or mallet endemic to Western Australia, widespread in subcoastal
areas from north of Murchison River south-east to Wagin, usually on
low hilly country. Bark rough on lower part of stems, dark grey to
grey-black. Adult leaves are glossy green. Inflorescences are distinct
in the many slender buds forming a spidery cluster.
Eucalyptus arachnaea 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. arachnaea is one of a group of 7 species that form series
Levispermae subseries Phaenophylla characterized by
having smooth sub-spherical seed, a peduncle that widens apically,
buds that are narrowly fusiform with some stamens erect and others
variably deflexed, and glossy green leaves.
The rough bark, very elongated buds (to 1.8 cm long) with operculum
recurved at the tip and narrower than the hypanthium at the join and
the seedling leaves with warty margins distinguish E. arachnaea
from other glossy-leaved species.
There are two subspecies:
subsp. arachnaea
The more widespread mallee form which occurs over the whole of the
species' distribution apart from the most inland sites.
subsp. arrecta (Latin, arrectus, upright, referring
to the tree form compared with the typical mallee form).
The mallet form that is only known from west of Morawa, south-east
of Geraldton, in relatively high, stony, hilly country where it forms
small pure stands emergent from the more dominant lower mallee scrub
of the area.
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