Botanical name

Acacia sp. Nullagine (B.R. Maslin 4955)

Description

Erect, openly branched shrubs 3 m tall. Bark exfoliating in a pseudo Minni Ritchi fashion, i.e. grey but reddish beneath. Branchlets mostly glabrous but sometimes sparsely hairy at very extremities, the hairs appressed to sub-appressed (difficult to see without magnification). New shoots resinous (but not sticky when dry), moderately densely hairy. Stipules persistent on upper branchlets, soon deciduous, triangular, about 1 mm long. Phyllodes narrowly oblong to slightly elliptic, narrowed at base, 4-5 (-6) cm long, 5-8 mm wide, glabrous or besprinkled with minute, scattered, appressed to sub-erect hairs; parallel longitudinal nerves numerous, few anastomosing, the central nerve more prominent than the rest and with a sub-prominent nerve on either side and parallel to it, the nerves slightly scurfy, upper margin 2-nerved to just above the gland (but does not have the appearance of A. trachycarpa); abruptly narrowed to a ąobtuse apex, mucronate by a small conical hard innocuous point. Gland obscure, 0-1 mm above pulvinus. Inflorescences simple, 1 per axil; peduncles very short (1-3 mm long), densely hairy, the hairs rather coarse and patent; spikes short (7-10 mm long when dry). Flowers 5-merous; calyx divided for about ź-1/3 its length into oblong, ciliolate lobes, the tube with ąsparse and sub-patent hairs; petals glabrous or sub-glabrous, ąobscurely 1-nerved. Pods not seen.

Characteristic features

Shrubs. Bark pseudo Minni Ritchi fashion. Stipules persistent on upper branchlets, soon deciduous, triangular, about 1 mm long. Phyllodes ąnarrowly oblong, narrowed at base, relatively short and broad (mostly 4-5 cm x 5-8 mm), ąglabrous; nerves numerous and parallel, a few anastomosing, the nerves slightly scurfy; apex ąobtuse, mucronate. Inflorescences simple; peduncles very short (1-3 mm), densely hairy, the hairs rather coarse and patent; spikes short (7-10 mm). Pods not seen.

Distribution and ecology

Confined to the Pilbara region in northwest Western Australia where it is known from a single collection about 30 km north of Nullagine. Grows in a low-lying area between rocky hills on rocky clay.

Flowering and fruiting period

The single gathering to hand was in full flower at the end of June. Judging from this specimen it seems likely that flowering would extend from about late May to the end of July. Pods not seen.

Affinities

The sub-persistent stipules and bark characters suggests affinities with A. trachycarpa; the short peduncles with dense wide-spreading hairs suggest affinities with A. eriopoda. Acacia eriopoda x trachycarpa hybrids do occur in the Pilbara and are described elsewhere in this work; these hybrid plants have long, narrow, linear phyllodes. Although Acacia sp. Nullagine (B.R. Maslin 4955) grows with A. trachycarpa and A. eriopoda grows nearby, it is not an obvious hybrid between these two species, except for the presence of pseudo Minni Ritchi bark. All other hybrids involving A. trachycarpa that have been seen possess, in addition to pseudo Minni Ritchi bark, phyllodes with a widened upper margin (about twice the width of the lower margin); in Acacia sp. Nullagine (B.R. Maslin 4955) the upper and lower margins are of equal width. Further study is needed to determine the taxonomic status of this entity; however, it is unlikely to represent a distinct species.

Conservation status

Acacia sp. Nullagine (B.R. Maslin 4955) is listed as a Priority 1 taxon on the Department of Environment and Conservation's Declared Rare and Priority Flora List.

Origin of name

The phrase name Acacia sp. Nullagine (B.R. Maslin 4955) identifies this taxon at the W.A. Herbarium.