The grass genera of the world
Habit, vegetative morphology. Perennial; caespitose. The flowering culms leafy. Culms 110 cm high (or more?); woody and persistent; branched above. Primary branches 4–10; horizontally aligned. Culm leaf sheaths present; persistent; not conspicuously auriculate. Culm leaves with conspicuous blades. Culm leaf blades triangular. Culm internodes hollow. Unicaespitose. Rhizomes pachymorph. Plants unarmed. Leaves not basally aggregated; auricles minute, rudimentary or obsolete; with auricular setae. Leaf blades narrow; to about 1 mm wide; acicular (aculeiform, to 9 cm long); pseudopetiolate; without cross venation; disarticulating from the sheaths. Ligule present (very short, dorsally canescent); a fringed membrane to a fringe of hairs. Contra-ligule present.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. The spikelets all alike in sexuality.
Inflorescence. Inflorescence open; spatheate (inflorescence branches subtended by bracts, but no prophylls except when the racemes are reduced to single spikelets); a complex of partial inflorescences and intervening foliar organs. Spikelet-bearing axes persistent. Spikelets not secund; pedicellate.
Female-fertile spikelets. Spikelets morphologically conventional, or unconventional (the number of glumes variable); 70–400 mm long; compressed laterally; disarticulating above the glumes; tardily disarticulating between the florets. Rachilla prolonged beyond the uppermost female-fertile floret; hairy, or hairless; the rachilla extension with incomplete florets. Hairy callus absent.
Glumes present, or absent; when present, one per spikelet to several (consisting of leaf sheaths with reduced blades, but varying from species to species in form, number, and spatial relation to the first lemma); relatively large; very unequal to more or less equal; shorter than the adjacent lemmas, or long relative to the adjacent lemmas; free; awnless. Spikelets with incomplete florets. The incomplete florets both distal and proximal to the female-fertile florets. The distal incomplete florets merely underdeveloped. Spikelets with proximal incomplete florets. The proximal incomplete florets 1–2 (?). The proximal lemmas awned, or awnless; exceeded by the female-fertile lemmas; similar in texture to the female-fertile lemmas.
Female-fertile florets (1–)3–15. Lemmas acuminate; not becoming indurated (papery); entire; pointed; awnless, or mucronate, or awned. Awns when present, 1; apical; non-geniculate; much shorter than the body of the lemma. Lemmas hairy, or hairless; carinate, or non-carinate (but then keeled towards the tip); several nerved. Palea present; relatively long; not convolute; apically notched (and 2 or 4 dentate); awnless, without apical setae; not indurated (papery); 2-nerved; 2-keeled. Lodicules present; free; membranous; ciliate; not toothed; heavily vascularized. Stamens 3 (occasionally 3–6 in A. diversa). Anthers not penicillate; without an apically prolonged connective. Ovary apically glabrous, or apically hairy; with a conspicuous apical appendage. The appendage broadly conical, fleshy. Styles fused. Stigmas 2 (rarely showing a vestigial third).
Fruit, embryo and seedling. Fruit longitudinally grooved; compressed dorsiventrally. Hilum long-linear. Embryo small.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae present; costal and intercostal. Intercostal papillae from the ends of the interstomatals over-arching the stomata (and almost enclosing them); several per cell (a single, median row of large, circular or bifurcated papillae per long-cell). Long-cells markedly different in shape costally and intercostally (the costals much more regularly rectangular); of similar wall thickness costally and intercostally. Mid-intercostal long-cells rectangular; having markedly sinuous walls (with conspicuous pits). Microhairs present; elongated; clearly two-celled; panicoid-type; 42–51 microns long; 7.5–10.5 microns wide at the septum. Microhair total length/width at septum 5–6.8. Microhair apical cells 21.6–24 microns long. Microhair apical cell/total length ratio 0.42–0.57. Stomata common; 28.5–31.5 microns long. Subsidiaries obscured. Intercostal short-cells common; in cork/silica-cell pairs and not paired; not silicified (in the silica-deficient material seen). Costal short-cells predominantly paired. Costal silica bodies poorly developed; rounded (but most of the very few silica bodies in the material seen poorly developed).
Transverse section of leaf blade, physiology. C3. Mesophyll without adaxial palisade; with arm cells (these very conspicuous); without fusoids (sic). Leaf blade more or less nodular in section (the adaxial ribs low, round- to flat-topped). Midrib conspicuous (as indicated by a distinct longitudinal fold nearer to one margin of the lamina); with one bundle only. The lamina distinctly asymmetrical on either side of the midrib (assuming the fold is indicative of a laterally displaced midrib). Bulliforms present in discrete, regular adaxial groups (a conspicuous group in each adaxial groove); in simple fans (a few only), or associated with colourless mesophyll cells to form deeply-penetrating fans (most of the groups being associated internally with a large, deeply-penetrating median colourless cell). All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present; forming figures (nearly all the bundles with a conspicuous I or anchor). Sclerenchyma not all bundle-associated. The extra sclerenchyma in abaxial groups and in adaxial groups (there being occasional abaxial groups opposite the bulliforms, and single layers of fibres lining the bulliforms -cf. Atractantha); abaxial-hypodermal, the groups isolated and adaxial-hypodermal, contiguous with the bulliforms.
Classification. Watson & Dallwitz (1994): Bambusoideae; Bambusodae; Bambuseae. Soreng et al. (2015): Bambusoideae; Bambusodae; Bambuseae; Guaduinae. 4 species.
Distribution, phytogeography, ecology. Brazil.
References, etc. Leaf anatomical: studied by us - A. cannavierira (Alvarado de Silviera) McClure.
Illustrations. • A. arenicola: McClure (1973). • A. arenicola (details): McClure (1973). • A. diversa: McClure (1973). • A. cannavierira (Filgueirasia), abaxial epidermis of leaf blade: this project. • A. cannavierira, abaxial epidermis of leaf blade, detail). • Abaxial epidermis of leaf blade (A. cannavierira, stomata): this project. • A. cannavierira, transverse section of leaf blade: this project). • A. cannavierira, transverse section of leaf blade margin: this project)
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: 11th December 2017. delta-intkey.com/grass’.