Avena fatua L., Sp. Pl. 80 (1753).

Vegetative form. Annual, erect or geniculate, caespitose. Leaves mostly basal. Culms 35-125(-160) cm high, unbranched above, 2-3 noded. Mid-culm nodes glabrous, exposed, not pigmented, constricted. Mid-culm internodes hollow, glabrous, terete. Young shoots intravaginal. Leaves non-auriculate. Basal leaf sheaths keeled (upper part), terete, glabrous or pubescent, the same colour as the lamina or purple, with the veins equally striate, with margins free, membranous, smooth. Ligule 2-6 mm long, not lobed, decurrent, membranous, smooth or ciliolate (obscurely), obtuse, erose, abaxially hairy. Collar glabrous. Distinct callus at blade-sheath junction absent. Leaf blades joining the sheath gradually, flat, linear, 120-300(-450) mm long, 4-11(-15) mm wide; adaxially glabrous or adaxially scabrous, not grooved; abaxially glabrous or abaxially scabrous, with midrib prominent; with margins scabrous or with margins scabrous and with margins ciliate (near base), apices acute; convolute in bud. Prophyll 15-20 mm long, glabrous.

Reproductive organization. Plants bisexual. Rudimentary spikelets at the base of the inflorescence, or absent. Incomplete spikelets absent. Inflorescence of chasmogamous spikelets (?).

Inflorescence. Inflorescence a panicle, pallid, green, and brown, nodding, open, symmetrical, partially exserted or fully exserted. Main inflorescence axis 295-850 mm long. Peduncles 225-580 mm long, glabrous, smooth or ridged (slightly). Rachides 70-270 mm long, terete, glabrous. Pulvini present. Primary inflorescence branches glabrous or scabrous (lightly); paired or clustered, branching at the base or not branched at the base, spreading to reflexed, distichous. Spikelets 1-2 on a typical ultimate inflorescence branch, on first order branches or on second order branches, pendulous.

Hermaphrodite (`perfect') spikelets. Hermaphrodite spikelets pedicellate, 18-25(-30) mm long, 15-20 mm wide, laterally compressed, cuneate, not disarticulating as a separate unit, disarticulating above the glumes. Pedicels 4-50 mm long, slender (distally dilated), scabrous. Glumes two per spikelet, similar, equal in length or subequal, exceeding the florets, longer than the proximal lemma. Lower glume narrowly oblong to narrowly ovate, 19-27(-30) mm long, 2.5-3 mm wide, membranous, dorsally rounded, subulate, entire, muticous, margin smooth; (7-)8-10 veined, veins prominent (with obscure transverse veins), midvein glabrous; intercostal regions glabrous. Upper glume narrowly oblong to narrowly elliptic, (18-)22-30 mm long, 2.5-3 mm wide, membranous, dorsally rounded, subulate, entire, muticous, margin smooth; (7-)9-11 veined, veins prominent (with obscure transverse veins), midvein glabrous; intercostal regions glabrous. Rudimentary florets distal to the hermaphrodite florets. Incomplete florets absent. Hermaphrodite florets 2-3 per spikelet. Rachilla disarticulating between the florets, disarticulating directly below the florets, straight, segments 1.7-2.6 mm long, silky, elongated between all florets, apically prolonged; prolongation silky, 3.4-4.3 mm long, terminated by a rudimentary floret. Callus present, blunt, 1.6-1.8 mm long, silky (hairs golden-brown), hairs to 5 mm long. Lemma decidedly firmer than the glumes, laterally compressed, narrowly oblong to narrowly ovate, 16-22 mm long, 2-2.6 mm wide, coriaceous, not keeled, obtuse to truncate, bidentate, 2 -lobed (lobes often ending in short bristles); apex membranous; awned. Lemma margins membranous; smooth. Lemma 7(-9) veined. Lemma veins not confluent apically, prominent (near the apex), the laterals raised and the marginals raised, connected by obscure transverse veins, scaberulous and silky, with the hairs on all the veins, with the hairs extending the length of the veins (scabrid above, silky below awn insertion); intercostal regions scaberulous and silky, the hairs over the entire dorsal surface (scabrid above, silky below awn insertion). Awns 1, median. Median awn much longer than the body of the lemmas (c. twice the lemma), 33-48 mm long, 1 veined, terete, dorsal; 10-14.5 mm below tip; arising from the mid-point of the lemma to from the lower half of the lemma, geniculate, column twisted (stout, dark brown or black when mature), scabrous. Palea fully developed, slightly shorter than the lemmas, thinner than the lemmas, narrowly elliptic, 12.7-15.3 mm long, 2.6-3.6 mm wide, membranous and coriaceous (slightly), 2-keeled, keels wingless, acute or obtuse, apically notched or bidentate (shortly), margin smooth; 2 veined, veins ciliate (hairs to 0.4 mm long, straight, soft); intercostal regions puberulous. Lodicules 2, free, hyaline, ovate, acute, smooth, with entire margins, glabrous. Stamens 3. Anthers 3.6-6 mm long, yellow, entire or shortly basally 2-lobed. Ovary antrorsely silky, with the hairs over the entire ovary. Styles 2, apical, free to their bases.

Fruit. Fruit free from both lemma and palea, oblong, ventrally compressed, 7.2-8.5 mm long, 2.1-2.4 mm wide, longitudinally grooved, silky, with dense hairs, the hairs covering most of the body, with a fleshy apex. Hilum linear. Embryo 2.6-3 mm long, not waisted, with an epiblast; endosperm hard.

Common name. Wild Oats.

Distribution. Introduced. Tasmania, New South Wales, Australian Capital Territory, Victoria, Western Australia, Queensland, Northern Territory, and South Australia. World distribution: Mediterranean.

Ecology. Mesophytic; in open habitats. Common weed of disturbed ground and cereal crops. Flowers July-Oct. Fruits ?-Dec.

Vouchers. Specimens examined morphologically: W.A.: Rabbit Proof Fence Rd, 48.8 km due SE of Wubin, brown clayey sand at roadside to open pasture, occasional in Acacia dominated shrubland, erect grass to 0.2 m high, 22 Sept. 1985, N.Hoyle 353 (CANB!, PERTH). S.A.: Emu, introduced near an old settlement on a calcrete platform, a bluish grass, very erect and with weeping heads, 22 Sept. 1956, N.Forde 557 (CANB). N.T.: 37 mi [59.6 km] SE of Yuendumu Native Settlement, dominant in small patches in coarse desert loam, with Triodia pungens, erect annual 18 in. high, 16 July 1956, M.Lazarides 6010 (CANB). Qld: 46 km from Inglewood on Inglewood Warwick road, roadside, 3 Sept. 1975, B.K.Simon 2862, L.Pedley & W.McDonald (BRI, CANB!). N.S.W.: Condobolin, 11 km E on Parkes Rd, 11 Oct. 1990, N.Lloyd 997 (CANB). A.C.T.: Black Mtn, Canberra, roadside, planted with white clover as erosion control on road to TV station, 25 Nov. 1964, M.Gray 5601 (CANB); O'Connor, Canberra, disturbed waste area near roadside, growing with 5312 (A. ludoviciana), 12 Dec. 1962, R.Pullen & M.Gray 5313 (CANB).

Classification. Pooideae; Poodae; Aveneae.

References. Morphology: S.W.L.Jacobs & S.M. Hastings; Morris 62 (1991).

Cite this publication as:
C.M. Weiller, M.J. Henwood, J. Lenz and L. Watson (1995 onwards). `Pooideae (Poaceae) in Australia - Descriptions and Illustrations'. URL http://muse.bio.cornell.edu/delta/
Dallwitz (1980) and Dallwitz, Paine and Zurcher (1993) should also be cited.

References and Acknowledgements