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BrancMets terete, pale green and slightly pruinose to pale yellowish green when dry, 
occasionally with a pinkish tinge when young, sometimes becoming encrusted with a 
brownish to blackish material with age, glabrous, with very low rounded ridges; 
axillary branchlets subtended by two caducous bracts (which usually leave fine scars 
on the stem when shed). Phyllodes sessile, patent to slightly inclined, ± straight, 
± quadrangular in section (to ± terete), with a yellow or pale-coloured vein at apex of 
each angle and a less prominent vein on the intervening faces (± 8-veined altogether, 
however, the intermediate veins are often incomplete not reaching the apex, obscure, 
wrinkle-like or not apparent, hence the phyllodes often appearing c. 4-veined), (1.5-) 
2-4 (-4.5) cm long, 1-1.2 (-1.3) mm wide, rigid, light green (dry), glabrous (immature 
phyllodes with scattered, appressed, white-hyaline hairs), gradually tapered towards 
a pungent-pointed apex (the fine tip orange-brown and 1.5-3.5 mm long), abruptly 
broadened or splayed at base 2-6 mm wide (leaving an oval-obovate scar on branchlet 
when lost), with a small ± circular gland on upper margin or vein near (or to 3 mm 
above) base and often a second minute gland c. V3-V3 from base; galls with a shape that 
is hakea fruit-like are commonly formed within some phyllodes. Inflorescences 
normally paired (often one of the peduncles missing) or sometimes single on a 
rudimentary raceme axis to 1 mm long (often appearing simple); peduncles 5-21 mm 
long, glabrous; bracts at base of peduncles deeply convex, ± broadly ovate, often with 
a split or minor lobe/peak about midway below either side of the apex, to 2 mm long, 
sparsely ciliolate, often caducous; heads globular, 17-25-flowered, 5-7 mm diam. 
(dry), cream-coloured to pale yellow. Bracteoles ± obovate to broadly spathulate, 
0.9-1.1 mm long, ciliolate, with scattered minute hairs also on the outer surface of the 
claw especially along midline (which is often not central). Flowers 5-merous; calyx 
cupular, 0.8-1.2 mm long, dissected for 14 (-16) or less, with minute hyaline-white hairs 
at base and often scattered on tube or concentrated along ribs, ciliolate along the 
obtuse to broadly rounded lobes; corolla dissected for V3-V2 or more, probably splitting 
towards base with age, the petals 1.5-1.9 mm long, 1-veined, glabrous or with 
inconspicuous, minute hairs or granules at apex mainly on margin, acute and often 
purplish in upper half; ovary glabrous to white-puberulous. Pods and seeds not seen. 
(Fig. 1). 
Phenology: flowers recorded in May and July. No pod formation was observed during 
latter stages of flowering in mid-July 2000 (Hawes et ah 2000) and no pods were found 
in early November 2000 (T. Tame, pers. comm.). Although A. atrox has often been seen 
in flower in past years, pods have not been observed (W. Pollock, pers. comm.) and it 
is possible that they are rarely, if ever, produced. 
Etymology: the specific epithet reflects the fierce or severe character of the plant 
created by the prominent pungent-pointed foliage. 
Distribution: known only from a single collection site on Myall Creek Station, 18 km 
S of Delungra, west of InvereU, North Western Slopes, New South Wales. 
Habitat: grows in deep clay soils, on basalt, on the upper slope and crest of a low hill, 
at head of a drainage depression, in a partly cleared paddock with Eucalyptus 
moluccana-E. aliens Box woodland with a scattered understorey of Callitris glaucophylla 
and Notelaea microcarpa and a dense native grassy groundcover. Although the area has 
been used as native pasture for grazing stock, much of the woodland community is of 
mixed age and healthy condition with minor weed invasion (Hawes et al. 2000). 
Conservation status: known only from the type locality. Provisionally listed under the 
informal name Acacia sp. 'Myall Creek' (Millar s.n. 25 May 2000) as an Endangered 
Species on Part 1 of Schedule 1 of the NSW Threatened Species Conservation Act, 1995. 
Acacia atrox warrants a 2E or 2V classification on the ROTAP list (Briggs & Leigh 1996), 
depending on the degree of risk posed by present and future land uses in the area. 
