The grass genera of the world
Habit, vegetative morphology. Delicate perennial; caespitose. The flowering culms leafy. Culms 15–50 cm high; herbaceous; to 0.1 cm in diameter; unbranched above. Culm nodes glabrous. Plants unarmed. Leaves not basally aggregated (the lower and middle culm leaves with reduced blades, the upper leaves fully developed in dense, pinnately presented complements of 3–15); auriculate (via a small, distal prolongation on one side of the sheath); without auricular setae. Sheaths slightly keeled. Leaf blades linear to lanceolate (acuminate); broad to narrow; (3–)10–30 mm wide (and (60-)80–160 mm long); flat; pseudopetiolate (the cuneate, slightly asymmetrical blade base attenuate to the 1–2 mm pseudopetiole); persistent (?). Ligule an unfringed membrane (ciliolate); truncate; 0.3–0.6 mm long.
Reproductive organization. Plants monoecious with all the fertile spikelets unisexual; without hermaphrodite florets. The spikelets of sexually distinct forms on the same plant; female-only and male-only. The male and female-fertile spikelets on different branches of the same inflorescence, or segregated, in different parts of the same inflorescence branch (having a clavately pedicelled female spikelet terminating a racemose panicle which bears several to many male or male and female spikelets on erect filiform pedicels below, or occasionally with a short, erect branch from the lower part of the inflorescence bearing two male spikelets).
Inflorescence. Inflorescence determinate; without pseudospikelets; few spikeleted to many spikeleted; a single raceme, or paniculate; spatheate (the male branch, when present, often bearing a minute bract), or espatheate (?); a complex of partial inflorescences and intervening foliar organs, or not comprising partial inflorescences and foliar organs (?). Spikelet-bearing axes racemes, or paniculate. Spikelets not secund (?); pedicellate.
Female-sterile spikelets. The male spikelets early deciduous, 7–8 mm long, linear, hyaline. The male spikelets without glumes; without proximal incomplete florets; 1 floreted. The lemmas awned (the awn flexuous, 1–2 mm long). Male florets 1.
Female-fertile spikelets. Spikelets 11–15 mm long; narrowly lanceolate; falling with the glumes (or the glumes tardily disarticulating); with conventional internode spacings. Rachilla terminated by a female-fertile floret. Hairy callus absent.
Glumes two; more or less equal (the lower slightly longer, even in situ); exceeding the spikelets; long relative to the adjacent lemmas (exceeding them); hairy to hairless (glabrous to puberulent); pointed; long awned; non-carinate; similar (firmly membranous, lanceolate, attenuate into the stiff, scabrous, 2.5–8 mm awns, with cross nerves). Lower glume 5 nerved. Upper glume 3 nerved. Spikelets with female-fertile florets only; without proximal incomplete florets.
Female-fertile florets 1. Lemmas ellipsoidal or lanceolate; decidedly firmer than the glumes (leathery); not becoming indurated; pale, becoming mottled with dark spots; entire; pointed; mucronate to awned. Awns 1; median; apical; non-geniculate; straight; hairy (short-pilose); much shorter than the body of the lemma (1–1.5 mm long). Lemmas hairy (with appressed, silky hairs); non-carinate; having the margins inrolled against the palea; perhaps with a clear germination flap (judging from the illustration in Zuloaga and Judziewicz 1993). Palea present; relatively long; tightly clasped by the lemma (and hidden by it, except at the base). Palea back hairy.
Classification. Watson & Dallwitz (1994): Bambusoideae; Oryzodae; Olyreae. Soreng et al. (2015): Bambusoideae; Bambusodae; Olyreae; Olyrinae. 1 species (A. lancifolia).
Distribution, phytogeography, ecology. Amazonian South America.
Mesophytic; shade species; glycophytic. Wet lowland forests.
References, etc. Morphological/taxonomic: Zuloaga and Judziewicz 1993.
Special comments. Segregated from Olyra (O. lancifolia Mez). Available description poor. Fruit data wanting. Anatomical data wanting.
We advise against extracting comparative information from the descriptions. This is much more easily achieved using the DELTA data files or the interactive key, which allows access to the character list, illustrations, full and partial descriptions, diagnostic descriptions, differences and similarities between taxa, lists of taxa exhibiting or lacking specified attributes, distributions of character states within any set of taxa, geographical distribution, and classifications. See also Guidelines for using data taken from Web publications.
Cite this publication as: ‘Watson, L., Macfarlane, T.D., and Dallwitz, M.J. 1992 onwards. The grass genera of the world: descriptions, illustrations, identification, and information retrieval; including synonyms, morphology, anatomy, physiology, phytochemistry, cytology, classification, pathogens, world and local distribution, and references. Version: 13th November 2017. delta-intkey.com/grass’.