Common name
Feathertop Threeawn
Feathertop
Unequal Threeawn

Derivation
Aristida L., Sp. Pl. 1: 82 (1753); from the Latin arista (an awn).

inaequiglumis- from the Latin inaequalis (unequal) and gluma (husk), alluding to the unequal glumes.

Published in
Biblioth. Bot. 85: 347 (1915).

Habit
Perennial, tufted. Culms 32–155 cm tall, 1-noded. Mid-culm internodes glaucous, smooth, glabrous. Lateral branches sparsely branched. Leaf-sheaths longer than adjacent culm internode, smooth or scaberulous, glabrous on surface. Ligule a fringe of hairs, 1 mm long. Collar glabrous. Leaf-blades curled, flat or conduplicate or involute or convolute, 15–30 cm long, 2.3–4.5 mm wide. Leaf-blade venation comprising 7 vascular bundles. Leaf-blade surface scabrous.

Inflorescence
Inflorescence compound, a panicle. Panicle contracted, lanceolate, equilateral or nodding, 13–40 cm long, 1.5–4 cm wide. Primary panicle branches appressed, moderately spaced, 4-nate, 4–8 cm long, bearing spikelets almost to the base. Panicle branches smooth or scaberulous.

Spikelets
Spikelets solitary. Fertile spikelets 1-flowered, comprising 1 fertile floret, without rhachilla extension, lanceolate, terete, 9–18.5 mm long, breaking up at maturity. Spikelets disarticulating below each fertile floret. Floret callus elongated, 0.9–1.5 mm long, pubescent, acute.

Glumes
Glumes lower deciduous, upper persistent or deciduous, similar, thinner than fertile lemma. Lower glume lanceolate, 9–18.5 mm long, 140% length of upper glume, membranous, 1-keeled, 1(–3)-nerved. Lower glume lateral nerves absent. Lower glume surface smooth to scabrous, glabrous. Lower glume apex acute or acuminate, mucronate. Upper glume lanceolate, 6.4–13 mm long, 140–170% of length of adjacent fertile lemma, membranous, 1-keeled, 1-nerved. Upper glume lateral nerves absent. Upper glume surface glabrous. Upper glume apex entire or erose, emarginate or acute or acuminate or cuspidate, mucronate.

Florets
Fertile lemma lanceolate, subterete, 3.7–9 mm long, coriaceous, pallid and light brown, 3-nerved. Lemma surface smooth or scaberulous or scabrous, rough above. Lemma margins involute, covering most of palea, without distinctive roughness or tuberculate (along groove). Lemma apex acute, 3-awned. Median (principal) awn pseudo-articulate at base, 14–46 mm long, without a column, persistent. Lateral lemma awns present, 11–40 mm long, subequal to principal or shorter than principal, 85% of length of principal. Palea 20% of length of lemma, without keels. Anthers 3. Grain with adherent pericarp, grooved, 3.1–7 mm long. Embryo 25–50% of length of grain. Hilum linear, 40–50% of length of caryopsis.

Continental Distribution:
Australasia.

Australian Distribution:
Western Australia, Northern Territory, South Australia, Queensland.

Western Australia: Fitzgerald, Hall, Dampier, Mueller, Canning, Giles, Helms, Fortescue, Austin. Northern Territory: Darwin & Gulf, Barkly Tableland, Victoria River, Central Australia North, Central Australia South. South Australia: North-western, Lake Eyre. Queensland: Cook, Burke, North Kennedy, South Kennedy, Gregory North, Gregory South, Mitchell, Warrego.

Classification. (GPWG 2001):
Aristidoideae

Notes
Native. Also in a few outlying areas in Western Australia, South Australia and Queensland. Acacia, Callitris, Eucalyptus and Astrebla communities on red earths, sands and alluvial soils. Flowering and fruiting all year. Aristida inaequiglumis is closely allied to Aristida pruinosa in having inverse glumes which differ in length by more than 3 mm long. It differs from this species by being less robust and less pruinose, having a distinct pseudoarticulation and leaf blades which curl up at maturity. The lemma groove is almost always tuberculate, although there are a few records of specimens with smooth lemma grooves. It is recorded from more arid sites than Aristida pruinosa. It differs from Aristida ingrata by the glumes differing in length by more than 3 mm.