Acacia orthocarpa F.Muell., J. Proc. Linn. Soc., Bot . 3: 136 (1859)
Slender, diffuse and often weeping or sometimes bushy and low-spreading, resinous shrub or small tree to 4 m high. Bark smooth or flaky, grey, dark grey or grey-brown. Branchlets slightly angular, brown, glabrous, with conspicuous lenticels; ridges inconspicuous. Phyllodes straight to curved, terete to subterete, 2.5–15.6 cm long, 0.5–1 mm wide, with rounded margins, coriaceous, glabrous, with conspicuous stomates; nerves obscure or midnerve and lateral 2 longitudinal nerves semiprominent; gland 1 or absent, basal, to 2.6 mm above pulvinus. Spikes 0.9–3.2 cm long, yellow. Flowers 5-merous; calyx 0.5–0.8 mm long, dissected for 1/2–4/5, thin, glabrous; corolla 0.9–1.4 mm long, dissected for 2/5–3/5, glabrous; ovary glabrous. Pods erect, mostly linear-oblanceolate to linear, basally tapered, straight-sided, slightly biconvex to almost subterete, 3–10 cm long, 3–8 mm wide, woody, longitudinally nerved, opening elastically from apex. Seeds longitudinal or slightly oblique, oblong-elliptic, 4.3–6 mm long, dark brown; areole open; funicle-aril narrowly conical.
Occurs in tropical Australia, in the Dampier–Sahara–Mt Anderson and Fitzroy Crossing–Gordon Downs–Wyndham areas of W.A., in mainly central N.T., and in the Lawn Hill–Mount Isa, Galilee and Georgetown–Gilberton areas of Qld. Grows on sandy flats, rocky hills and in rocky watercourses, in savannah woodland and eucalypt shrubland, often with spinifex. Flowers most of the year.
In W.A., there is some variation in phyllode shape from terete to subterete, with the latter character tending towards the closely related species, A. arida . Acacia arrecta is related to these two species. Acacia filamentosa is possible distantly related to A. orthocarpa . Superficially resembling A. tenuissima but the two species are not closely related.
A collection from the North Pilbara Region, W.A., made in the Abydos/Woodstock Reserve, possibly represents a hybrid with this species and A. ancistrocarpa , the putative parents ( K.L.Tinley 3244 , PERTH).
Type of accepted name
McArthur R., [N.T.], F.Mueller 4 ; holo: MEL n.v. ; iso: K.
Synonymy
Racosperma orthocarpum (F.Muell.) Pedley, Austrobaileya 2: 353 (1987). Type: as for accepted name.
Acacia xylocarpa A.Cunn. ex Benth., London J. Bot. 1: 370 (1842), nom. illeg. , non Willd. (1806). Type: Dampiers Arch., W.A., Feb. 1818, A.Cunningham 119 ; holo: K; iso: BM n.v.
Acacia pityoides F.Muell., J. Proc. Linn. Soc., Bot. 3: 135 (1859). Type: Sturt’s [Sturt] Ck, [W.A./N.T], F.Mueller 5 ; lecto: MEL, fide L.Pedley, Proc. Roy. Soc. Queensland 75: 34 (1964); isolecto: K.
Illustrations
F.Mueller, Iconogr. Austral. Acacia dec. 10 [pl. 7] (1888), as A. pityoides , as to flowering branchlet, floral and carpological details and left hand pyllode detail, fide L.Pedley, loc. cit. (1964); F.Mueller, op. cit. 11 [pl. 8], as A. xylocarpa ; J.R.Wheeler, in J.R.Wheeler (ed.) et al ., Fl. Kimberley Region 318, fig. 92D (1992).
Representative collections
W.A.: Cherrabun Stn, S of Fitzroy Crossing, J.S.Beard 6956 (NSW, PERTH); 1 mile [1.6 km] E of turnoff to Port Hedland, I.V.Newman 678 (NSW). N.T.: c. 46 miles [74 km] N of Tennant Creek, J.R.Maconochie (NSW, NT, PERTH) ; 61.2 km S of Dunham R. on Great Northern Hwy, M.D.Tindale 10144, P.Munns & R.Turley (BRI, DNA, MEL, MO, NSW, PERTH). Qld: L. Moondarra, Mount Isa, R.G.Coveny 480 (CANB, NSW, US); Lawn Hill Stn, P.K.Latz 1602 (NSW, NT).
(NSW)
The information presented here originally appeared on the WATTLE CD-ROM which was jointly published by the Australian Biological Resources Study, Canberra, and the Department of Parks and Wildlife, Perth; it was produced by CSIRO Publishing from where it is available for purchase. The WATTLE custodians are thanked for allowing us to post this information here.
