Avena sterilis L., Sp. Pl. (1753).

Vegetative form. Annual, erect or geniculate, caespitose. Leaves mostly basal. Culms 55-160 cm high, unbranched above, 3-5 noded. Mid-culm nodes hairy or glabrous, exposed, pigmented or not pigmented, constricted. Mid-culm internodes hollow, glabrous or pubescent (immediately below node), terete. Young shoots intravaginal. Leaves non-auriculate. Basal leaf sheaths distally keeled or not keeled, terete, glabrous or scabrous or pubescent to pilose, with the veins equally striate, with readily visible transverse veins, with margins free, membranous, smooth or ciliate. Ligule 2.5-8 mm long, not lobed, decurrent, membranous or chartaceous to carnose, smooth, obtuse, entire or erose (slightly), abaxially glabrous or hairy. Collar glabrous. Distinct callus at blade-sheath junction absent. Leaf blades joining the sheath gradually, flat, linear, 80-420 mm long, 4-14 mm wide, stiff; adaxially glabrous to adaxially scabrous (lightly), shallowly grooved; abaxially glabrous to abaxially scabrous (lightly), with midrib prominent; with margins scabrous or with margins ciliate (hairs to 2.1 mm long, clearly separated), apices acuminose (gradually tapering to a point); 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 cleistogamous spikelets (?).

Inflorescence. Inflorescence a panicle, pallid and green, nodding, open, symmetrical, fully exserted. Main inflorescence axis 295-920 mm long. Peduncles 170-610 mm long, glabrous, slightly ridged. Rachides 105-440 mm long, terete, glabrous. Pulvini present. Primary inflorescence branches scabrous; paired or clustered, branching at the base or not branched at the base, spreading or divaricate or reflexed, distichous. Spikelets 1-2 on a typical ultimate inflorescence branch, on first order branches or on second order branches, pendulous, spreading.

Hermaphrodite (`perfect') spikelets. Hermaphrodite spikelets pedicellate, 20-45 mm long, 15-25 mm wide, laterally compressed, cuneate, not disarticulating as a separate unit, disarticulating above the glumes (between the upper glume and lowest lemma only). Pedicels 10-60 mm long, recurved, slender (distally dilated), antrorsely scabrous, straight. 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, 20-50 mm long, 2-4 mm wide, membranous to chartaceous, dorsally rounded, subulate, entire, muticous, margin smooth; (7-)9-11 veined, veins prominent, midvein glabrous; intercostal regions glabrous. Upper glume narrowly oblong to narrowly ovate, 20-50 mm long, 2-4 mm wide, membranous to chartaceous, dorsally rounded, subulate, entire, muticous, margin smooth; (7-)9-11 veined, veins prominent, midvein glabrous; intercostal regions glabrous. Rudimentary florets distal to the hermaphrodite florets. Incomplete florets absent. Hermaphrodite florets 2-3 per spikelet, dark brown at maturity or golden-brown at maturity. Rachilla not disarticulating between the florets (but may fracture below the upper florets), straight, segments 0.9-2.5 mm long, glabrous or papillose to scabrous, shortly elongated between the upper glume and first floret and elongated between all florets, apically prolonged; prolongation 4-5 mm long, terminated by a rudimentary floret. Callus present, blunt, 1.2-2.6 mm long, silky (hairs pale golden), hairs to 7.5 mm long. Lemma decidedly firmer than the glumes, laterally compressed, narrowly oblong to narrowly ovate, 15-33 mm long, 2-3 mm wide, coriaceous, not keeled, subulate, bifid, 2 -lobed or 4 -lobed (lobes occasionally with a short bristle); apex membranous; awned (upper floret unawned). Lemma margins membranous; smooth or ciliolate (obscurely). Lemma 7 veined. Lemma veins not confluent apically, prominent (at the apex), the laterals raised and the marginals raised, connected by obscure transverse veins, scaberulous and silky (upper floret glabrous), with the hairs on all the veins, with the hairs extending the length of the veins (scabrous near the apex, antrorsely long silky below the point of awn insertion); intercostal regions glabrous or silky or scaberulous and silky (upper floret glabrous), the hairs over the entire dorsal surface or only at the base. Awns 1, median. Median awn much longer than the body of the lemmas (more than twice the lemma length), 30-80 mm long, 1 veined, terete, dorsal; 10-21.2 mm below tip; arising from the mid-point of the lemma or from the lower half of the lemma (c. 1/3 the lemma length from the base), geniculate, column twisted (stout, pale brown), scabrous. Palea fully developed, slightly shorter than the lemmas or 2/3s the length of the lemma, thinner than the lemmas, narrowly ovate to narrowly elliptic, 12.7-19.6 mm long, 2.5-3.8 mm wide, firmly membranous to coriaceous (the lateral faces hyaline to membranous), 2-keeled, keels wingless, acute or obtuse, shortly bidentate, margin smooth; 2 veined, veins ciliolate (hairs dense, to 0.4 mm long, extending most of the keel length); sparsely intercostal regions puberulous. Lodicules 2, free, hyaline, ovate or triangular, acute, smooth, with entire margins, glabrous. Stamens 3. Anthers yellow, entire or shortly basally 2-lobed (1/8-1/10). Cleistogamous anthers 2.6-4.3 mm long. Ovary obovoid, antrorsely silky, pale-golden. Styles 2, apical, free to their bases.

Fruit. Fruit free from both lemma and palea, oblong, ventrally compressed, 7.6-9 mm long, 2.1-2.6 mm wide, longitudinally grooved, silky, with dense hairs, the hairs covering most of the body, with a fleshy apex. Hilum 5.5-7.7 mm long, linear. Embryo 2.6-3.8 mm long, not waisted, with an epiblast; endosperm hard.

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

Ecology. Mesophytic. Weed of roadsides. Flowers Sept.-Dec. Fruits Sept.-Dec.-?.

Classification. Pooideae; Poodae; Aveneae.

References. Morphology: S.W.L.Jacobs & S.M. Hastings.

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