Brachyachne ambigua*

Brachyachne ambigua* Ohwi. Bull. Tokyo Sci. Mus. 18: 11 (1947).

Classification. (GPWG 2001) : Subfamily Chloridoideae. Cynodonteae.

Type of Basionym or
Protologue Information
: HT: Dorzelo 3169, Dec 1924, Java: Gersik,
east Java, on low rocky hill (BO; IT: L).

Key references
(books and floras):
[2002] D.Sharp & B.K.Simon, AusGrass, Grasses of
Australia
.

Illustrations:
[2005] K.Mallet (ed.), Flora of Australia 44B: Poaceae 3 (Fig.
50F-J).

Habit. Annual. Stolons
absent. Culms geniculately ascending or decumbent, 30–55 cm tall. Ligule an
eciliate membrane, 0.3 mm long, truncate. Leaf-blades 1–10 cm long, 1 mm wide.
Leaf-blade surface glabrous.

Inflorescence.
Inflorescence digitate, with spicate branches.

Spikelets.
Spikelets sessile. Fertile spikelets 1-flowered, comprising 1 fertile
floret(s), without rachilla extension, lanceolate or oblong, laterally
compressed, 2–3.5 mm long.

Glumes. Glumes
similar, firmer than fertile lemma. Lower glume lanceolate, coriaceous, keeled,
1-keeled, wingless, 1 -nerved. Upper glume lanceolate, 2–3.5 mm long,
coriaceous, keeled, 1-keeled, wingless, 1 -nerved.

Florets.
Fertile lemma 1.8–2 mm long, keeled, 3 -nerved. Lemma surface indumented. Lemma
apex muticous. Palea 2 -nerved. Grain 1–1.6 mm long.

Continental
Distribution
: Tropical Asia and Australasia.

Australian
Distribution
: Western Australia, Northern Territory.

Western Australia:
Gardner. Northern Territory: Darwin & Gulf.

Notes.
A weed of rice crops in northern Australia.

 Plants of B. ambigua closely resemble
those of B. tenella but differ by the compressed (not turgid) grain, the
approximate (almost contiguous) keels of the palea, somewhat longer glumes, and
in characteristic plants by the absence of indumentum between the nerves of the
lemma. In spikelet structure it is more like B. convergens, which
differs by its usually bearded sheath auricles, larger spikelets, winged
glumes, and relatively short floret.

Introduced;
confined to the N of the N.T. within 350 km of Darwin, and NE W.A. near the
border; recorded from Java, Lesser Sunda Is., Papua, and northern Australia.
Australian plants occur as weeds of cultivation or disturbed sites, usually in
heavy-textured black soils of sub-coastal plains and river flood plains, often
in association with B. convergens.

 

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