The grass genera of the world
Habit, vegetative morphology. Perennial; rhizomatous and decumbent. Culms 12–40 cm high; herbaceous; unbranched above. Culm nodes glabrous. Culm internodes solid. Plants unarmed. Leaves not basally aggregated; non-auriculate. Sheaths longer than the internodes. Leaf blades linear-lanceolate to lanceolate; narrow; to 2.5 mm wide; flat (rigid, pungent-tipped); without abaxial multicellular glands; without cross venation; persistent. Ligule present; a fringed membrane to a fringe of hairs. Contra-ligule absent.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. The spikelets all alike in sexuality (except perhaps for depauperate spikelets at the inflorescence tip).
Inflorescence. Inflorescence of spicate main branches; fairly open. Primary inflorescence branches 12–20 (or more); inserted all around the main axis (irregularly disposed around the axis on four sides, by contrast with Bouteloua). Inflorescence with axes ending in spikelets. Rachides triquetrous, ridged. Inflorescence espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes with very slender rachides; persistent. Spikelets solitary; secund; biseriate.
Female-fertile spikelets. Spikelets 2 mm long; adaxial; compressed laterally (but the individual florets dorsally compressed); disarticulating above the glumes; the rachilla somewhat elongated beneath the crown of sterile florets. Rachilla prolonged beyond the uppermost female-fertile floret; hairless; the rachilla extension with incomplete florets. Hairy callus present. Callus short.
Glumes two; very unequal; shorter than the adjacent lemmas (somewhat); dorsiventral to the rachis; hairless; glabrous; pointed; awnless (but G2 mucronate); carinate; very dissimilar (both hyaline, G1 pointed, G2 acuminate). Lower glume 1 nerved. Upper glume 1 nerved. Spikelets with incomplete florets. The incomplete florets distal to the female-fertile florets. The distal incomplete florets 3–5; clearly specialised and modified in form (clustered at rachilla tip, reduced to their lemmas, these each deeply incised into three long, divergent, equal awns and the awns of all the lemmas forming a crown). Spikelets without proximal incomplete florets.
Female-fertile florets 1. Lemmas decidedly firmer than the glumes (thinly membranous); not becoming indurated; incised; 3 lobed (the lobes attenuate into the awns); deeply cleft; awned. Awns 3; median and lateral; the median different in form from the laterals (curved back); apical; non-geniculate; recurving; hairless (scabrid); about as long as the body of the lemma; entered by one vein. The lateral awns shorter than the median (upright). Lemmas hairy (on the back and along lateral nerves); non-carinate; without a germination flap; 3 nerved. Palea present; relatively long; tightly clasped by the lemma; entire (spathulate); awnless, without apical setae (glabrous); thinner than the lemma; not indurated (hyaline); 2-nerved; 2-keeled. Palea keels wingless; scabrous. Lodicules present; 2; free; tiny and delicate; glabrous; not or scarcely vascularized. Stamens 3. Anthers very short; not penicillate; without an apically prolonged connective. Ovary apically glabrous. Styles free to their bases. Stigmas 2; red pigmented.
Fruit, embryo and seedling. Fruit free from both lemma and palea; small (to about 1.5 mm long); ellipsoid; trigonous. Hilum short. Pericarp fused. Embryo large.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous (the intercostal regions sunken). Papillae present; costal and intercostal. Intercostal papillae over-arching the stomata (slightly, at one end, sometimes), or not over-arching the stomata; consisting of one oblique swelling per cell (involving interstomatals), or consisting of one symmetrical projection per cell (elsewhere, these small, circular, usually displaced towards on end of the cell). Mid-intercostal long-cells having markedly sinuous walls. Microhairs present; more or less spherical to elongated; clearly two-celled; chloridoid-type. Microhair apical cell wall of similar thickness/rigidity to that of the basal cell. Microhairs 24–27(–30) microns long. Microhair basal cells 12 microns long. Microhairs 9–10.5–12 microns wide at the septum. Microhair total length/width at septum 2.3–2.9. Microhair apical cells 7.5–9(–12) microns long. Microhair apical cell/total length ratio 0.28–0.38. Stomata common; 19.5–21–22.5 microns long. Subsidiaries dome-shaped and triangular. Guard-cells overlapped by the interstomatals (slightly). Intercostal short-cells absent or very rare (apparently). Intercostal silica bodies absent. Costal short-cells conspicuously in long rows (but the short-cells quite long in some files). Costal silica bodies present in alternate cell files of the costal zones; almost exclusively saddle shaped; not sharp-pointed.
Transverse section of leaf blade, physiology. Lamina mid-zone in transverse section open.
C4; XyMS+. PCR sheaths of the primary vascular bundles interrupted; interrupted abaxially only. PCR sheath extensions absent. Leaf blade nodular in section; with the ribs more or less constant in size. Midrib conspicuous; having a conventional arc of bundles (with a small bundle on either side of the large median); with colourless mesophyll adaxially. Bulliforms present in discrete, regular adaxial groups (the groups not very conspicuous); seemingly exclusively in simple fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present (with all the bundles); forming figures (all the bundles). Sclerenchyma all associated with vascular bundles. The lamina margins with fibres.
Classification. Watson & Dallwitz (1994): Chloridoideae; main chloridoid assemblage. Soreng et al. (2015): Chloridoideae; Cynodonteae. 2 species (N. lophostachya, N. pauciracemosa).
Distribution, phytogeography, ecology. Argentina.
Species of open habitats. Dry plains and hillsides.
References, etc. Leaf anatomical: studied by us - N. lophostachya (Griseb.) Gould.
Illustrations. • N. lophostachya: Parodi (1919), Las Chlorideas de la Republica Argentina. • N. lophostachya, abaxial epidermis of leaf blade: 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’.