Aristida hygrometrica

Aristida hygrometrica R.Br. Prodr. 174

Classification. (GPWG 2001) : Subfamily Aristidoideae.

Type of Basionym or
Protologue Information
: LT: R. Brown 6196, 14 Feb 1803, Australia:
Northern Territory: Darwin & Gulf Region, Arnhem North Bay (Melville Bay)
(BM; ILT: BRI (fragm., photo ex BM), E, K). LT designated by Henrard, Meded.
Rijks Herb
. 54(A): 248 (1927).

Key references
(books and floras):
[1810]. R.Brown, Prodromus (174), [1878]
G.Bentham, Flora Australiensis 7, [1952] C.A.Gardner, Flora of
Western Australia
1 Gramineae (165), [2002] D.Sharp & B.K.Simon,
AusGrass, Grasses of Australia.

[1952] C.A.Gardner, Flora of Western Australia 1 Gramineae (167,
Pl. 49), [1983] J.C.Tothill & J.B.Hacker, Grasses of Southern Queensland

Derivation: Gk.
water; metron, measure; -ike, belonging to. Aquatic or swamp

Habit. Annual.
Culms erect or geniculately ascending, 29–84 cm tall. Mid-culm internodes
glabrous. Lateral branches simple or sparsely branched or branched.
Leaf-sheaths smooth, glabrous on surface or hairy. Ligule a fringe of hairs,
0.5 mm long. Leaf-blades curled or flexuous, filiform, conduplicate or involute
or convolute, 11–27 cm long, 0.8–1.2 mm wide. Leaf-blade surface scabrous.

Inflorescence compound, a panicle. Panicle elliptic, 14.4–35 cm long, 7–15 cm

Spikelets pedicelled. Fertile spikelets 1-flowered, comprising 1 fertile
floret(s), without rachilla extension, lanceolate, terete, 25–43 mm long.

Glumes similar, thinner than fertile lemma. Lower glume lanceolate, membranous,
keeled, 1-keeled, 3 -nerved. Lower glume surface glabrous. Upper glume
lanceolate, 25–42.6 mm long, membranous, keeled, 1-keeled, 1 -nerved. Upper
glume surface glabrous. Upper glume apex awned.

Fertile lemma 8–16 mm long, without keel, 3 -nerved. Lemma apex awned, 3
-awned. Median (principal) awn 138–235 mm long overall, with a twisted column.
Column 53–85 mm long. Lateral lemma awns present. Palea without keels. Anthers
3. Grain 6.6–8.5 mm long.

: Australasia.

: Western Australia, Northern Territory, Queensland.

Western Australia:
Gardner, Fitzgerald, Hall, Dampier. Fortescue. Northern Territory:
Darwin & Gulf, Victoria River, Barkly Tableland, Central Australia North. Queensland:
Burke, Cook, Mitchell, North Kennedy, South Kennedy.

A. hygrometrica differs from A. holathera and A. contorta
by larger spikelet dimensions all round especially the length and thickness of
the column.

Mainly north of lat.
20 S with a few isolated southern records in Western Australia and the Northern
Territory. Sandy and alluvial soils and often the dominant grass on extensive
river levees. Often in Eucalyptus and Melaleuca woodland.
Flowering and fruiting January to August, November.

AVH 2011


Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith