Acacia hamiltoniana Maiden
Acacia hamiltoniana Maiden
Occurs in the Great Divide and its foothills from near Rylstone S to the Clyde R. near Nerriga, N.S.W.
Bushy shrub normally to 3 m high. Branchlets finely ribbed, dark red, glabrous. Phyllodes mostly ascending to erect, often patent at ends of branchlets, variable, linear to linear-oblanceolate or narrowly elliptic, (2-) 3–6 (-8) cm long, usually 2.5–5 mm wide, narrowed at base, glaucous to subglaucous, glabrous, 1-nerved; lateral nerves ±absent; gland not prominent, 0–7 mm above pulvinus. Inflorescences racemose; raceme axes 0.5–5 cm long, glabrous; peduncles 2.5–5 mm long, glabrous; heads globular, subdensely 9–15-flowered, golden; bracteole laminae transversely elliptic, dark brown, white-fimbriolate. Flowers 5‑merous; sepals united; petals 1-nerved. Pods to 5.5 cm long, 7-10 mm wide, firmly chartaceous to thinly coriaceous, ±black, glabrous. Seeds oblique (end ones sometimes longitudinal) oblong to elliptic to ovate, 4–5 mm long, somewhat shiny, black; aril clavate.
Grows in sand or sandy loam on sandstone outcrops in Eucalyptus forest or woodland and heath.
N.S.W.: 2 km ESE of Sassafras on Nowra–Nerriga road, B.G.Briggs 3004 & D.Blaxell (NSW); Currant Mtn Gap, 24 km by road E of Rylstone, R.Coveny 6618 & P.Hind (NSW, PERTH); Bell (Mt Wilson road), 28 Sept. 1912, A.A.Hamilton (NSW); Du Faurs Rocks, Mt Wilson, B.R.Maslin 5887 (MEL, MEXU, NSW, PERTH).
Some specimens from Mt Wilson in the Blue Mtns (e.g. R.Coveny 2902, CANB, NSW, PERTH) are atypical in having phyllodes which are very narrow (1.5–2 mm wide) and/or acuminate (normally obtuse-mucronulate to acute).
Related to A. obtusata which is distinguished especially by its wider phyllodes (5–16 mm), gland generally farther above the pulvinus (5–40 mm), 15–27-flowered heads and longitudinal seeds. The flower-heads of these two species have a distinctive facies, i.e. the 1-nerved petals of adjacent flowers overtop the dark brown bracteoles and are not contiguous when in bud; A. hakeoides and A. williamsonii are similar but are distinguished by their narrower pods and glands further above the pulvinus.
The nomenclature of A. hamiltoniana is linked to that of A. adunca and is discussed by L.Pedley, Austrobaileya 1: 286 (1980), and B.R.Maslin, Telopea 6: 43–47 (1994).
Habit may resemble that of A. decora, a species possessing a distinctive, often golden pubescence on its peduncles and raceme axes.
Data derived from Flora of Australia Volumes 11A (2001), 11B (2001) and 12 (1998), products of ABRS, ©Commonwealth of Australia
Minor edits by B.R.Maslin & J.Rogers
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