Holcus* Sp. Pl. 1047 (1753).
Derivation:. An old Latin name for a type of grain.
Key references (keys and floras):. G.Bentham, Flora Australiensis 7: 585–586 (1878); C.A.Gardner, Flora of Western Australia 1 Gramineae 41–42 (1952); J.C.Tothill and J.B.Hacker, Grasses of Southern Queensland 264–265 (1983); J.P.Jessop, Flora of South Australia 4: 1912 (1986); B.K.Simon, Key to Australian Grasses 124 (1993);S.W.L.Jacobs and K.L.McClay, Flora of New South Wales 4: 593–594 (1993); N.G.Walsh, Flora of Victoria 2: 457–459 (1994); D.I.Morris, Student's Flora of Tasmania 4B: 243–245 (1994); E.Edgar and H.E.Connor, Flora of New Zealand 5: 315–317 (2000); D.Sharp and B.K.Simon, AusGrass (2002); J.P.Jessop, Grasses of South Australia 224–226 (2006); S.W.L.Jacobs, R.D.B.Whalley & D.J.B.Wheeler, Grasses of New South Wales, 4th ed, 274–275 (2008); A.Wilson (ed.), Flora of Australia 44A: Poaceae 2: 137–140 (2009).
W.D.Clayton & S.A.Renvoize, Genera Graminum (1986), genus (188).
Naturalised. 6 species, from Canary Is., North Africa, Europe to Asia Minor & Caucasus; 1 in South Africa. 4 species in Australia, WA, SA, Qld, NSW, Vic, and Tas. Also Malesia and New Zealand.
Habit. Annual (rarely) or perennial, rhizomatous to stoloniferous or tufted. Leaf blades broad or narrow. Ligule an unfringed membrane.
Inflorescence. Inflorescence paniculate, a spike-like panicle, fairly open to contracted.
Spikelets. Spikelets laterally compressed, 2 flowered, with 1 fertile floret, awned, solitary; with naked rachilla extension (and sometimes prolonged beyond the upper, male-only floret). Fertile spikelets falling with glumes, usually with a distinctly elongated rachilla internode above glumes (with the lower floret elevated on a curved internode).
Glumes. Glumes more or less equal, about equal to spikelet to exceeding florets (enclosing them), long relative to adjacent lemmas, pointed, keeled, similar (membranous). Lower glume 1 nerved. Upper glume 3 nerved.
Florets. Fertile florets 1 (very rarely, both florets hermaphrodite). Lemmas decidedly firmer than glumes (leathery or cartilaginous, shiny), entire at apex or incised, when entire pointed or blunt, muticous or awned, indistinctly 3–5 nerved, hairy or glabrous, 1 keeled. Awns when present, 1, dorsal, geniculate. Palea relatively long, tightly clasped by lemma, textured like lemma, 2 nerved. Distal incomplete florets 1, specialised and modified (male, falling entire). Callus very short. Lodicules 2. Stamens 3. Grain small, longitudinally grooved (rarely) or not grooved, compressed laterally. Hilum short, or long-linear (rarely). Embryo small.
Kranz Anatomy. C3.
2n = 8, 14, 28, 35, 42, and 49, 2, 4, 5, 6, and 7 ploid, commonly adventive.
Habitat. Mesophytic. Grassland, open woodland, disturbed ground. Shade species and species of open habitats.
Classification. Pooideae; Poeae.
Notes. Holcus intergrades with Deschampsia and the relationship between the genera is akin to that between Helictotrichon and Arrhenatherum (Clayton and Renvoize 1986).
Types Species. H. lanatus L., typ. cons..
Biogeographic Element. Clifford & Simon 1981, Simon & Jacobs 1990: Naturalised.