Acacia spinosissima Benth.
Acacia spinosissima Benth.
Scattered from Cadoux S to Brookton and E to near Lake King, south-western W.A.
Intricate compact or spreading glabrous shrub 0.2–1.5 m high. Branches substriate by ribs, ±pruinose. Branchlets numerous, short, spreading, spinescent, commonly aphyllous. Phyllodes sometimes with some subfasciculate on short branchlets, ascending to erect, ±narrowly oblong, straight or very shallowly sigmoid, usually 3–8 mm long, 1–2 mm wide, excentrically mucronulate, green; midrib obscure or slightly raised; lateral nerves absent. Inflorescences rudimentary 1-headed racemes with axes < 0.5 mm long; peduncles 4–12 mm long; heads globular, usually 3–3.5 mm diam. 7–18 (–23)-flowered, bright lemon yellow; bracteoles absent or few. Flowers 5-merous; sepals united into a ±truncate calyx; petals nerveless. Pods prominently rounded over seeds on alternate sides, to 6 cm long, 3–5 mm wide, thinly coriaceous, pruinose. Seeds longitudinal, oblong, 2.5 mm long, dark brown, verruculose; aril clavate.
Grows in sand or sometimes clay loam.
W.A.: Gairdner Reserve, S of Tammin, R.Cumming 1346 (PERTH); 17 km due NE of Brookton, R.J.Hnatiuk 790150 (PERTH); 42 km NE of Coujinup Hill, M.A.Burgman 1331 & S.McNee (CANB, PERTH); 1.6 km S of Cadoux towards Manmanning, B.R.Maslin 139 (PERTH).
Acacia spinosissima often resembles A. erinacea in its spinose branchlets and small phyllodes, but A. erinacea has whitish scurfy phyllodes, bracteolate, heads with more flowers, and very different pods and seeds. The absence of bracteoles is a possible link to A. rostellata. Sometimes confused with A. ulicina or A. jacksonioides.
The robust variant is a spreading shrub 0.5–1.5 m high; phyllodes 4–8 (rarely to 15) mm long, 1–2 mm wide; peduncles 5–12 mm long; heads 4–6 mm diam., 10–18 (–23)-flowered; petals 2–2.5 mm long; pods 4–5 mm wide; seeds not seen. It is known only from near Cadoux, Tammin, Boorabbin and Lake King in south-western W.A. (representative collections: M.A.Burgman 1331 & S.McNee; B.R..Maslin 139).
The typical variant is a compact shrub 0.2–0.4 m high; phyllodes 3–7 mm long, c. 1 mm wide; peduncles 4–6 mm long; heads 3–3.5 mm diam., 7–10-flowered; petals 1.5–1.7 mm long; pods 3–3.5 mm wide. It is known only by collections from near Brookton, Tammin, Wyalkatchem, Muntadgin, Bruce Rock and Holt Rock in south-western W.A. (representative collections: R.Cumming 1346; R.J.Hnatiuk 790150).
Two variants are recognised and may ultimately be shown to warrant formal rank.
Data derived from Flora of Australia Volumes 11A (2001), 11B (2001) and 12 (1998), products of ABRS, ©Commonwealth of Australia
Minor edits by J.Rogers
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