Holcolemma Bull. Misc. Inform. 244 (1929).
Derivation:. From Greek holcus (groove) and lemma, alluding to the grooved lower lemma.
Taxonomic revisions, nomenclatural references:. O.Stapf & C.E.Hubbard, Bull. Misc. Inform. 8: 244–247 (1929); W.D.Clayton, Kew Bull. 42: 401–403 (1987).
Key references (keys and floras):. B.K.Simon, Key to Australian Grasses 124 (1993); D.Sharp and B.K.Simon, AusGrass (2002).
W.D.Clayton & S.A.Renvoize, Genera Graminum (1986), genus (505).
Native. 4 species, from East Africa, southern India, Sri Lanka and Queensland. 1 species in Australia, Qld.
Habit. Annual or perennial, loosely tufted (with a knotty rootstock and geniculately ascending culms). Leaf blades narrow. Ligule an unfringed membrane.
Inflorescence. Inflorescence paniculate, a racemose panicle with spikelets all similar, contracted.
Spikelets. Spikelets dorsally compressed, 2 flowered, with 1 fertile floret, (at least at the branch tips) subtended by solitary bristles, solitary. Fertile spikelets with lower incomplete floret(s), abaxial (with lower glume on side away from rachis), falling with glumes.
Glumes. Glumes unequal (lower glume a quarter, upper glume a half the spikelet length), shorter than spikelet, shorter than adjacent lemmas, hairless, pointed or blunt, awnless, non-keeled, similar (membranous or chartaceous). Lower glume 3 nerved. Upper glume 3–5 nerved or 13 nerved.
Florets. Lower incomplete floret(s) male, or sterile. Lemmas doubly saccate, with a deep, grooved fold down the back, awnless, 5–13 nerved, more or less equalling fertile lemmas to exceeding fertile lemmas (the upper lemma sometimes much the shorter), less firm than fertile lemmas to similar in texture to fertile lemmas (membranous or herbaceous), not becoming indurated. Palea of lower incomplete florets becoming conspicuously hardened and enlarged laterally (after anthesis, when the large leathery keels come to clasp the side of the upper floret). Fertile florets 1. Lemmas decidedly firmer than glumes, rugose, becoming indurated (thinly crustaceous) or not becoming indurated, entire at apex, pointed, muticous or mucronate, with a clear germination flap, 5 nerved, glabrous, having flat margins not tucked into palea. Palea relatively long, textured like lemma, indurated or not indurated, 2 nerved. Stamens 3. Grain small, compressed dorsiventrally. Hilum short. Embryo large.
Kranz Anatomy. C3.
Habitat. Weedy places. Shade species, or species of open habitats.
Classification. Panicoideae; Paniceae.
Notes. The palea keels principally distinguish the genus from Paspalidium, but do not assume their distinctive form until after anthesis (Clayton and Renvoize, 1986).
Types Species. H. canaliculatum (Nees) Stapf & C.E.Hubb.
Biogeographic Element. Clifford & Simon 1981, Simon & Jacobs 1990: Old World Tropics.