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Acacia douglasica

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Acacia douglasica Pedley (ms)

Trees to 5 m tall; bark corky. Branchlets with scattered straight hairs 0.3 mm long. Stipules on flowering stems, sparse, straight, 0.7–1.5 mm long, to 5 mm on young plants. Leaves: axis 40–75 mm long (including petiole 5–8 mm), with scattered to moderately dense hairs on the broadly sulcate surface; gland disc-like, situated between the lowest pair of pinnae; pinnae 11–22 pairs, 15–30 mm long; pinnules 20–35 pairs, oblong, 1.6–2.2 mm long, 0.5–0.7 mm wide, thick, veins obscure, glabrous or with a few marginal hairs. Heads globular, 15–30-flowered; peduncles 25–40 mm long, with scattered long hairs, involucel in upper half. Flowers 5-merous; calyx gamosepalous; corolla c. 3.2 mm long. Pods c. 65 mm long and 15 mm wide, described as ‘creamy-coloured’, somewhat pubescent but becoming black and glabrous with age. Seeds longitudinal, obloid, c. 10 mm long, c. 9 mm wide; pleurogram prominent, open; areole large, depressed.

Known only from the Douglas-Daly R. areas, N.T., where it occurs on cracking-clay soils.

Its closest relative is A. bidwillii with A. clarksoniana more distant. It has more pinnules per pinna and the pinnules are smaller than those of A. bidwillii . It lacks the rather dense indumentum of A. clarksoniana and has smaller flowers. Tindale & Kodela ( Austral. Syst. Bot. 9: 311, 1996) compared A. valida with A. ditricha but from a specimen (Tindale 6098) seen it seems that they included A. douglasica in their circumscription of A. ditricha .

There is considerable overlap in the dimensions of the vegetative parts of A. valida and A. douglasica Acacia valida has usually larger leaves with more pinnae and somewhat larger (usually wider) leaflets. The corollas of the two are about the same length, but the calyx of A. douglasica is about half the length of the corolla, whereas in A. valida  it is only about one-third of the length. A conspicuous difference is the larger petiolar gland of A. valida  and the presence of one or two additional smaller glands between the uppermost one or two pairs of pinnae; the rachis glands are absent in A. douglasica . The most conspicuous difference between the two, however, is the indumentum of the branchlets and axes of the leaves; "tomentose and velvety with long and short hairs" (Tindale & Kodela) in A. valida , and long and scattered in A. douglasica .

Type of accepted name

0.5km W of Douglas River, 1347’S, 13123’E, N.T., 23 Oct. 1974, M.Parker 508; holo: BRI; iso:DNA, CANB.


Acacia ‘Douglas R.’, Dunlop et al ., Flora of Darwin Region 2:20 t. 4 (1995)

A. ditricha auct. non Pedley; M.D.Tindale & P.Kodela, Austral. Syst. Bot. 9:311 (1996), pro parte.

Representative collection

N.T.: 2 Km E of Douglas R. on Ooloo rd, 1346’S, 13122’E, .M.O.Rankin 1232 (BRI, CANB, DNA, K, MEL, NSW, NT, PERTH).

(LP & BRM)

The species described here is based on text provided for use in WATTLE by L.Pedley; this taxon is noted in Fl. Australia under A. bidwillii.

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: Thursday 22 June 2023