The grass genera of the world
Habit, vegetative morphology. Perennial; rhizomatous and stoloniferous. Culms 20–60 cm high; herbaceous; unbranched above. Leaves not basally aggregated; non-auriculate. Leaf blades linear; narrow; about 5 mm wide; flat; not pseudopetiolate; without cross venation; persistent. Ligule an unfringed membrane; toothed. Contra-ligule absent.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets; exposed-cleistogamous and chasmogamous.
Inflorescence. Inflorescence paniculate; contracted; more or less irregular; espatheate; not comprising partial inflorescences and foliar organs. Spikelets not secund; pedicellate; imbricate.
Female-fertile spikelets. Spikelets 4–5 mm long; compressed laterally; disarticulating above the glumes; disarticulating between the florets; with conventional internode spacings. Rachilla prolonged beyond the uppermost female-fertile floret; hairy (between the florets, and above the upper one); the rachilla extension naked. Hairy callus present. Callus short; blunt.
Glumes two; very unequal to more or less equal; about equalling the spikelets; long relative to the adjacent lemmas; hairless; with scabrid keels; pointed; awnless; carinate; similar (lanceolate, membranous). Lower glume about equalling the lowest lemma; 1 nerved. Upper glume 3 nerved. Spikelets with female-fertile florets only; without proximal incomplete florets.
Female-fertile florets 1–2(–3). Lemmas oblong; decidedly firmer than the glumes (leathery or crustaceous); entire to incised; blunt; when incised, slightly 2 lobed; not deeply cleft; awnless; hairless; scabrous (above, shining below); non-carinate (dorsally rounded); without a germination flap; 5 nerved, or 7 nerved. Palea present; relatively long; tightly clasped by the lemma; entire to apically notched; awnless, without apical setae; thinner than the lemma (membranous); not indurated; 2-nerved; 2-keeled. Palea keels wingless; hairy (ciliate). Lodicules present; 2; free; membranous; glabrous (?); toothed. Stamens 3. Ovary apically apically hairy. Stigmas 2.
Fruit, embryo and seedling. Fruit small (about 1.75 mm long); ellipsoid; longitudinally grooved; somewhat compressed dorsiventrally, or not noticeably compressed; with hairs confined to a terminal tuft. Hilum short (but elongated, almost a third as long as the fruit). Embryo small. Endosperm hard.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Mid-intercostal long-cells fusiform; having straight or only gently undulating walls. Microhairs absent. Stomata common; 42–48 microns long. Subsidiaries parallel-sided. Guard-cells overlapped by the interstomatals. Costal short-cells conspicuously in long rows (in places), or neither distinctly grouped into long rows nor predominantly paired (in other places). Costal silica bodies horizontally-elongated crenate/sinuous (crenate, some short and approaching dunb-bells); not sharp-pointed.
Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll without adaxial palisade. Leaf blade with distinct, prominent adaxial ribs. Midrib with one bundle only. The lamina symmetrical on either side of the midrib. Many of the smallest vascular bundles unaccompanied by sclerenchyma. Combined sclerenchyma girders present. Sclerenchyma all associated with vascular bundles.
Classification. Watson & Dallwitz (1994): Pooideae; Poodae; Aveneae (?). Soreng et al. (2015): Pooideae; Poodae; Poeae; Calothecinae. 1 species (R. panicoides).
Distribution, phytogeography, ecology. Chile and Argentina.
Mesophytic; shade species. At margins of woods.
References, etc. Morphological/taxonomic: data from Nicora and Rúgolo de Agrasar 1987. Leaf anatomical: studied by us.
Illustrations. • R. panicoides: Nicora & Rúgolo de Agrasar (1987)
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’.