The grass genera of the world
Habit, vegetative morphology. Perennial; caespitose. Culms herbaceous. Culm nodes glabrous. Culm internodes solid. Leaves mostly basal, or not basally aggregated; non-auriculate. Leaf blades narrow; not cordate, not sagittate; flat; without cross venation; persistent.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets.
Inflorescence. Inflorescence of spicate main branches (slender racemes); open; digitate. Primary inflorescence branches 3–6. Rachides flattened. Inflorescence espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes persistent. Spikelets solitary; secund (on one side of the flattened rachis); biseriate; subsessile; rather not imbricate.
Female-fertile spikelets. Spikelets unconventional (either there is no L1 and only one glume, or both glumes are missing: the occasional presence of an apparent glume with terminal spikelets suggests that most spikelets lack both glumes); 2–5 mm long; lanceolate; abaxial; compressed dorsiventrally; planoconvex; falling with the glumes. The upper floret not stipitate. Rachilla terminated by a female-fertile floret. Hairy callus absent.
Glumes absent. Spikelets with incomplete florets (though the L1 could be mistaken for a glume). The incomplete florets proximal to the female-fertile florets. Spikelets with proximal incomplete florets. The proximal incomplete florets 1; epaleate; sterile. The proximal lemmas pointed to acuminate; awnless; 3 nerved; decidedly exceeding the female-fertile lemmas; less firm than the female-fertile lemmas to similar in texture to the female-fertile lemmas; not becoming indurated.
Female-fertile florets 1. Lemmas acuminate; not saccate; membranous to thinly leathery; striate (or scarcely so); entire; pointed; awnless; hairless; non-carinate; having the margins lying flat on the palea (except at the base); 3 nerved. Palea present; relatively long; gaping (free for nearly half its length); awnless, without apical setae; textured like the lemma; 2-nerved; 2-keeled (flat). Lodicules present; 2; free; fleshy; glabrous; not or scarcely vascularized. Stamens 3. Anthers not penicillate; without an apically prolonged connective. Ovary apically glabrous. Styles free to their bases. Stigmas 2; brown (dried).
Fruit, embryo and seedling. Fruit small. Hilum short. Embryo large.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Mid-intercostal long-cells having markedly sinuous walls. Microhairs present; panicoid-type. Stomata common. Subsidiaries dome-shaped (mostly), or triangular (rather indistinct). Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells common; in cork/silica-cell pairs. Costal short-cells conspicuously in long rows. Costal silica bodies panicoid-type; mostly nodular; not sharp-pointed.
Transverse section of leaf blade, physiology. C4; XyMS. Leaf blade nodular in section to adaxially flat; with the ribs more or less constant in size. Midrib not readily distinguishable; with one bundle only. Bulliforms not present in discrete, regular adaxial groups (indistinguishable from macrohair cushions, etc.). Many of the smallest vascular bundles unaccompanied by sclerenchyma. Combined sclerenchyma girders absent. Sclerenchyma all associated with vascular bundles.
Classification. Watson & Dallwitz (1994): Panicoideae; Panicodae; Paniceae. Soreng et al. (2015): Panicoideae; Panicodae; Paspaleae; Paspalinae. 4 species.
Distribution, phytogeography, ecology. Southern U.S.A. to Argentina.
Helophytic (mainly); glycophytic.
Rusts and smuts. Rusts Puccinia. Taxonomically wide-ranging species: Puccinia levis.
References, etc. Morphological/taxonomic: Hitchcock 1909. Leaf anatomical: this project.
Illustrations. • R. acuta (as brasiliensis): 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: 13th November 2017. delta-intkey.com/grass’.