Botanical name

Acacia sp. Marble Bar (J.G. & M.H. Simmons 3499)

Description

Shrubs. Branchlets scurfy, moderately to densely appressed hairy towards apex, indumentum sparser with age. New shoots resinous (but not sticky, at least when dry), ąsparsely white hairy. Phyllodes narrowly oblong to oblong-elliptic, (4.5-) 5-7 cm long, (6-) 8-10 mm wide, straight or some shallowly incurved, moderately to densely appressed -hairy, dull green; parallel longitudinal nerves numerous, central nerve more pronounced than the rest, often a sub-prominent nerves extends from the pulvinus to intersect the upper margin in lower ź of phyllode, the minor nerves close together with some longitudinally anastomosing, the upper margin slightly broader than lower margin (observe nerves at x10 magnification or higher); abruptly narrowed to an obtuse apex, mucronate by a short, conical, innocuous hard point. Gland situated on upper margin of phyllode at distal end of pulvinus. Inflorescences simple, 1 or 2 per axil; spikes 25-30 mm long, golden, the flowers sub- densely arranged; peduncles short (3-5 mm long), ąsparsely sub-appressed hairy; receptacle sparsely hairy, the hairs spreading to ąappressed. Flowers 5 merous; calyx 1/3 length of corolla, dissected for about ˝ its length; petals glabrous, obviously 1-nerved. Pods and seeds not seen.

Characteristic features

Shrubs. Branchlets scurfy, moderately to densely appressed hairy towards apex. Phyllodes narrowly oblong to oblong-elliptic, relatively short and broad (mostly 5-7 cm x 8-10 mm), moderately to densely appressed -hairy; parallel longitudinal nerves numerous with central nerve the most prominent, often a sub-prominent nerve extends from the pulvinus to intersect the upper margin in lower ź of phyllode, the minor nerves close together with some longitudinally anastomosing, the upper margin slightly broader than lower margin; apex obtuse-mucronate. Inflorescences simple; spikes with flowers sub- densely arranged; peduncles short (3-5 mm), sparsely to moderately sub-appressed hairy. Pods and seeds not seen.

Distribution and ecology

Confined to Pilbara region of northwest Western Australia where it is known for a single gathering near Marble Bar. Although no ecological information was provided by the collector we have visited the collection site which is located along a dry watercourse among low rocky hills in unconsolidated sand. The area had been recently burnt and much of the vegetation destroyed, which most probably accounts for our inability to relocate the plant(s) from which the original collection was made.

Flowering and fruiting period

Specimen with flowers at anthesis and in bud was collected in late September. Pods unknown.

Taxonomy

The taxonomic status of this entity is uncertain. The slightly widened upper margin of the phyllode suggests affinities to A. trachycarpa which grows close to where Acacia sp. Marble Bar (J.G. & M.H. Simmons 3499) was said to have been collected from. Indeed, this plant it may well be a hybrid involving A. trachycarpa , and if so we do not know what the other parent might be. The presence of a moderately dense indumentum of appressed hairs on the branchlets and phyllodes is unusual, as is the sub-prominent nerve that extends from the pulvinus to the upper margin.

Conservation status

There is insufficient information at present concerning this entity to justify including it on the Department of Environment and Conservation's Declared Rare and Priority Flora List.

Origin of name

The phrase name Acacia sp. Marble Bar (J.G. & M.H. Simmons 3499) identifies this taxon at the W.A. Herbarium.