Family

Fabaceae

Distribution

Occurs in coastal and near-coastal areas from the Young R. (c. 70 km due W of Esperance) to Israelite Bay (c. 180 km due E of Esperance) and extending inland to Truslove (c. 60 km due N of Esperance) and near Mt Buraminya (c. 130 km due NE of Esperance), south-western W.A.

Description

Glabrous multistemmed shrub, usually to 0.3 m high. Branchlets light grey, reddish at extremities. Stipules persistent, 1.5–3 mm long. Phyllodes dimorphic (on upper branches: terete, subterete, ±quadrangular or flat, 1–3 mm wide, pungent; on lower branches: frequently caducous, oblanceolate, flat, 1–6 (–7.5) mm wide, obtuse-mucronate), ascending to erect, 2–6.5 cm long, thickly coriaceous, drying with fine longitudinal wrinkles, often glaucous, 4-nerved in all, 1-nerved per face when flat; gland 6–7 mm above pulvinus. Inflorescences rudimentary, 1-headed racemes with axes c. 0.5 mm long, normally growing out; peduncles 12–22 (–30) mm long, thick; heads globular, 6.5–8 mm diam., mostly 36–53-flowered, golden. Flowers 5-merous; sepals free. Pods not constricted between the seeds, terete to subterete, to 8.5 cm long, 6–8 mm wide, hard and bony, ±pruinose. Seeds longitudinal, oblong to broadly elliptic, 4.5–5 mm long, dull, dark brown to black; aril terminal, pileiform.

Habitat

Grows in sand, gravelly sand, sand over clay, loam or clay, in open heath or open shrub mallee over heath, on flat or gently undulating topography.

Specimens

W.A.: 29 km W of Israelite Bay, H.Demarz 4919 (PERTH); Gibson’s Soak, L.Diels 5325 (PERTH); 35 km NNW of Young R. crossing on Ravensthorpe–Esperance main road, N.N.Donner 3018 (CANB, PERTH); 0.8 km N of Condingup Hill, c. 63 km E of Esperance, K.Newbey 7940 (PERTH).

Notes

Although Bentham described this taxon as a variety of A. gonophylla the two are not closely related. Acacia gonophylla is distinguished by its 5-nerved phyllodes, shorter peduncles, smaller, cream to pale yellow flower-heads and very different pods. Acacia pachyphylla is allied to A. dermatophylla which is normally a single-stemmed shrub with more prominent stipules, paired peduncles and broader pods; also similar superficially to A. maxwellii which has uniformly shaped phyllodes, mostly 1–3-headed reduced racemes, pale yellow to cream, smaller heads with many fewer flowers, united sepals and smaller, crustaceous pods enclosing ±circular seeds. The phyllodes of A. pachyphylla are generally similar to those of a S.A. species, A. pinguifolia, which has thick, 10–15-nerved phyllodes, simple or sometimes rudimentary, 1–3-headed reduced racemes, shorter peduncles and smaller heads with fewer flowers. Superficially similar also to A. mutabilis subsp. angustifolia.

FOA Reference

Data derived from Flora of Australia Volumes 11A (2001), 11B (2001) and 12 (1998), products of ABRS, ©Commonwealth of Australia

Author

Minor edits by J.Rogers

B.R.Maslin