Acacia difficilis Maiden, in A.J.Ewart & O.B.Davies, Fl. N. Territory 344; 387, pl. 27I–O (1917)
Shrub or tree, 2–12 m high. Bark of trunk and branches fibrous, grey-brown. Branchlets almost terete, grey-brown, densely pubescent or glabrous except in axils. Phyllodes elliptic to narrowly elliptic, with tapered base, very oblique, subfalcate, (5.5–) 7–14 cm long, 15–40 mm wide (to 20 cm long and 70 mm wide on young plants), thinly coriaceous, silvery-white and densely pubescent when young, later often glabrescent, with 5–9 prominent longitudinal nerves (ventral nerves becoming confluent with or near lower margin at base), the minor nerves 5–12 per mm, rarely anastomosing; gland 1, basal. Spikes 1.5–5 cm long, golden. Flowers 5-merous; sepals free, almost transparent, 0.6–0.8 mm long, silky-pubescent; corolla 1.2–1.4 mm long, dissected to c. 1/2, glabrous or slightly pubescent; ovary pubescent. Pods linear, not tumid, straight or curved, twisted, terete to subterete, 7–14 cm long, 3–4 mm wide, coriaceous, longitudinally striate; seed-partitions slightly oblique. Seeds longitudinal, oblong-elliptic, 5.5–7 mm long, 2–4 mm wide, black; pleurogram indistinct; areole open, depressed.
Common in N.T., N of 17S, on Melville and Thursday Is., rare in Kununurra area, W.A., also in Qld near the Gulf of Carpentaria. Grows usually in sandy or gravelly soils, often near creeks, frequently associated with Eucalyptus tetrodonta . Flowers Apr.–Oct.
Acacia difficilis is allied to A. tumida from which it is difficult to distinguish in herbarium material without pods. It is distinguished by the fibrous bark on both the trunks and branches as well as by its mostly thinner, often pubescent phyllodes, the slender stipes of the bracteoles, the calyces 0.6–0.8 mm long, the linear, narrower and nontumid pods and smaller seeds. Flowering specimens of A. lamprocarpa can be difficult to distinguish from glabrous forms of A. difficilis .
Details of ecology, utilisation, etc. of A. difficilis are given in J.W.Turnbull (ed.), Multipurpose Austral. Trees & Shrubs 130 (1986).
Type of accepted name
Howard Ck, 20 miles [32 km] SE of Darwin, N.T., 15 June 1916, G.F.Hill ; syn: NSW240680.
Racosperma difficile (Maiden) Pedley, Austrobaileya 2: 348 (1987). Type: as for accepted name.
Acacia tumida F.Muell. ex Benth., Fl. Austral . 2: 409 (1864), p.p. , not as to lectotype, as to paralectotype: Sturt Ck, F.Mueller 99 (MEL), fide L.Pedley, Contr. Queensland Herb . 15: 17 (1974).
J.H.Maiden, loc. cit .; J.Brock, Top End Native Pl . 59 (1988): C.R.Dunlop, G.J.Leach & I.D.Cowie, Fl. Darwin Region 2: 7, fig. 2 (1995); B.R.Maslin & M.W.McDonald, A key to useful Australian acacias for the seasonally dry tropics , CSIRO, 34 & 35 (1996).
W.A.: 27.5 km SE of Kununurra on Duncan Hwy, B.R.Maslin 5145 (BRI, DNA, PERTH). N.T.: Jim Jim Ck, M.Lazarides 7642 (BRI, CANB, DNA, K, L, NSW, US); Darwin R. Xing, Cox Penin. road, G.J.Leach 3257 (BRI, DNA, NSW, PERTH); 5 km NE of Cahills Crossing, towards Oenpelli, M.D.Tindale 10060 & P.Munns (DNA, MO, NSW). Qld: Thursday Is., W.S.Campbell 1911 (NSW).