Botanical name

Acacia pyrifolia var. morrisonii Maiden, J. & Proc. Roy. Soc. New South Wales 51: 248 (1917)

Common name

Morrison's Ranji

Aboriginal name

Thundu (Banyjima) or Bardirri (Kurrama)

Description

Obconic, glabrous shrubs (1-) 2-3.5 m tall, with about 4 main stems from near ground level, sometimes single-stemmed, main branches with an ascending aspect, crowns sub- open. Bark bronze except grey towards base of main stems, smooth. Branchlets green, yellow, yellow/green or brownish yellow, aging brown (tinged orange), not pruinose or infrequently faintly so (but pruinosity is not as conspicuous as on var. pyrifolia). New shoots pale green. Stipules spiny to sub-spiny, commonly brittle and breaking in about the middle with the lower half persistent, sometimes completely absent from some nodes, the spiny stipules sometimes persisting on old wood, 2-5 mm long, slender (less robust than often occurs in var. pyrifolia). Phyllodes obovate or elliptic to narrowly elliptic, broadest at or above the middle, 2-5.5 (-8) cm long, (1-) 1.5-2.5 (-4.5) cm wide, thinly coriaceous (less coriaceous than often occurs in var. pyrifolia), scarcely undulate, pale green or dull milky green, infrequently ąglaucous, not pruinose or rarely faintly so; midrib prominent and centrally located along centre-line of phyllode; terminal cusp slender and pungent. Gland situated on upper margin of phyllode 0-4 mm above the obscure pulvinus. Inflorescences elongated axillary racemes and terminal panicles that extend well beyond the phyllodes, the axes and peduncles not purple or red as in A. inaequilatera and A. marramamba; peduncles 6-15 (-20) mm long, twinned, sometimes with a rudimentary phyllode within their axil; heads globular, golden, densely 60-80-flowered; flower buds yellow or green. Flowers 5-merous; sepals free, linear-spathulate; petals glabrous and nerveless. Pods narrowly oblong, flat but rounded over seeds along midline and not or scarcely constricted between seeds, 2-9.5 cm long, 8-12 mm wide, firmly chartaceous, shallowly to strongly openly curved (into a semicircle), not pruinose, mid-brown; marginal nerve yellow. Seeds transverse, oblique or longitudinal in pods, obloid-ellipsoid to ellipsoid, turgid, 5-5.5 (-6) mm long, 4-4.5 mm wide, not shiny, dark brown, not mottled; areole very small (about 0.5 mm long) and obscure, 'u'-shaped, situated towards the base of the seed; pleurogram not bordered by yellow tissue; funicle flattened and somewhat thickened, folded at base of seed and not expanded into an aril.

Characteristic features

Obconic, glabrous shrubs with stems and main branches having an ascending (not widely spreading) aspect, crowns sub- open. Bark smooth, bronze except grey towards base of main stems. Branchlets normally not pruinose, if bloom developed then faint. Stipules spiny to sub- spiny, slender and commonly brittle. Phyllodes obovate or elliptic to narrowly elliptic, broadest at or above the middle (mostly 1.5-2.5 cm wide), dull milky green or sometimes ąglaucous, not pruinose or sometimes faintly so, midrib central, apical cusp slender and pungent. Inflorescences elongated axillary racemes and terminal panicles that extend well beyond the phyllodes; heads densely 60-80-flowered. Pods shallowly to strongly openly curved (into a semicircle), firmly chartaceous, not pruinose. Funicle flattened and somewhat thickened, not expanded into an aril.

Distribution and ecology

Occurs in northwest Western Australia where most records are from the Pilbara region. Current evidence shows this variety as having a scattered distribution from Nanutarra north to Mardi and Indee Stations, then east to the Nullagine-Newman area; it occurs along the Gascoyne River at Carnarvon and possibly also in the Rudall River National Park (see Variation below). As this variety becomes better known it is possible that it will be shown to be more common than current collections indicate (at least within the Pilbara). Variety morrisonii mostly grows along watercourses (creeks and rivers) in stony, unconsolidated colluvium under an overstorey of eucalypts and A. citrinoviridis.

Flowering and fruiting period

Flowers mainly in July and August, and pods with mature seeds having been collected in September and October.

Variation

The branchlets of var. morrisonii are normally not pruinose, however, pruinosity does sometimes occur, but it is weakly developed. Similarly, while the phyllodes of var. morrisonii are normally green, a few plants in some populations can be almost glaucous (and either not pruinose or faintly so). Plants with green phyllodes and non-pruinose branchlets sometimes co-occur with those having bluish green phyllodes and lightly pruinose branchlets. Specimens from the Rudall River (east of the Pilbara) may possibly represent this variety, however, they are characterized by atypically long stipules (7-12 mm) and further study is needed to ascertain their taxonomic status.

Taxonomy

Acacia pyrifolia comprises two varieties, var. pyrifolia and var. morrisonii, both of which occur in the Pilbara, but the former is the more common. Although Maiden (1917) and Domin (1926) independently described this taxon as A. pyrifolia var. morrisonii and A. morrisonii respectively, the name has not been taken up until now. Current evidence suggests that it is best treated as a variety of A. pyrifolia but the taxa are sometimes difficult to distinguish and further study is needed to further clarify their relationship. Variety pyrifolia can generally be distinguished from var. morrisonii by its often more diffuse, openly branched growth form (more 'gangly' and 'brambly'), normally conspicuously pruinose branchlets, generally more rigid and robust stipules, and its more thickly coriaceous, normally broader, often pruinose phyllodes that are infrequently broadest above the middle. Non-pruinose variants of var. pyrifolia do occur but these can normally be distinguished from var. morrisonii by the other characters just noted. Current evidence suggests that the two varieties are not sympatric.

Conservation status

Not considered rare or endangered.

Origin of name

The varietal name commemorates Alex Morrison, the first Western Australian Government Botanist (see Hall 1978 & Lamond and Bennell 1990 for biographical information). Morrison collected the type specimen of var. morrisonii on 6 October 1905 from the banks of the Ashburton River near Globe Hill. See under var. pyrifolia for discussion of confusion surrounding some common names.

References

Domin, K. (1926). Acacia. Bibliotheca Botanica 89: 249-276.

Hall, N. (1978). Botanists of the Eucalypts. pp. 180. (CSIRO: Melbourne.)

Lamond, J. and Bennell, A. (1990). Alexander Morrison (1849-1913) and Edinburgh's botanincal connections with Australia. pp. 149-155. In: P.S. Short (eds) History of systematic botany in Australasia. pp. 326. (Australian Systematic Botany Society Inc.)

Maiden, J.H. (1917). Notes on Acacia, No. 3 - Extra-Tropical Western Australia. With descriptions of new species. Journal and Proceedings of the Royal Society of New South Wales 51: 238-274.