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Acacia sessilis

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Acacia sessilis Benth., London J. Bot . 1: 336 (1842)

Diffuse shrub to c. 1 m high. New shoots minutely woolly. Branchlets spinose, minutely woolly, glabrescent. Stipules caducous but obvious on young new shoots, joined nearly to apex. Phyllodes patent to erect with some usually reflexed, usually acicular and terete to subterete, compressed to flat when dry, 7–25 mm long, usually 0.6–1.3 mm wide, pungent, rigid, green, with indumentum as on branchlets, usually 5-nerved with the 2 adaxial nerves coalescing 0.5–4.5 mm above pulvinus, 1- or 3-nerved per face when flat; pulvinus short but distinct. Inflorescences rudimentary 1-headed racemes with axes <0.5 mm long; peduncles 0–3 mm long; heads globular, 18–24-flowered, golden. Flowers 5-merous; sepals free, variably minutely woolly. Pods linear, to 5 cm long, 3.5–5 mm wide, crustaceous, minutely woolly; margins thick. Seeds longitudinal to oblique, normally broadly elliptic, c. 2.5 mm long, turgid, narrowed at periphery, mottled; aril small.

Occurs from Kalbarri Natl Park S to Yarloop, south-western W.A. Grows in sand or lateritic sand, in heath, sedgeland or low woodland.

Normally the phyllodes are terete to subterete and 5-nerved with the 2 adaxial nerves coalescing in the region of the gland. Upon drying these phyllodes flatten and have a central nerve on each face. A naturally occurring flat phyllode variant is found E of Leeman (e.g. C.Chapman 2 , PERTH) and this has narrowly oblong-elliptic phyllodes c. 10 mm long, 2 mm wide with 3 nerves per face; this variant resembles A. erioclada which has shorter, 1-nerved phyllodes and narrower pods.

Phyllode morphology of the typical variant closely resembles A. acuaria which is distinguished by glabrous or puberulous-hirsutellous branchlets, gamosepalous calyx and strongly curved to once-coiled pods. Related to A. benthamii .

Type of accepted name

Swan R., W.A., 1839, J.Drummond s.n. ; holo: K; iso: K.

Synonymy

Acacia sphacelata var. sessilis (Benth.) Benth., Fl. Austral . 2: 331 (1864). Type: as for accepted name.

[ Acacia sphacelata auct. non Benth.: M.Simmons, Acacias Australia 38 (1981); B.R.Maslin & L.Pedley, Res. Notes W. Austral. Herb. 6: 111 (1982); W.R.Elliot & D.L.Jones, Encycl. Austral. Pl . 2: 116 (1982)]

Illustration

M.Simmons, loc. cit.

Representative collections

W.A.: 6 km S of Kalbarri turn-off on North West Coastal Hwy, R.S. & R.A.Cowan A832 (CANB, K, NY, PERTH, US); Swan R., J.Drummond 301 (BM, G, K, MEL, P, PERTH, W); near Yarloop, F.W.Went 237 (PERTH); Gnangara road, c. 24 km due N of Perth, B.R.Maslin 2802 (K, PERTH).

(BRM)

WATTLE Acacias of Australia CD-ROM graphic

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.

Page last updated: Tuesday 11 September 2018