The grass genera of the world
Habit, vegetative morphology. Perennial; reedy (resembling Arundo and Phragmites in aspect); forming loose tufts. Culms 75–500 cm high; woody and persistent; branched above. Culm nodes glabrous. Culm internodes solid. Rhizomes pachymorph. Plants unarmed. Leaves not basally aggregated; non-auriculate. Leaf blades broad; 15–40 mm wide (often splitting longitudinally); without abaxial multicellular glands; without cross venation; disarticulating from the sheaths. Ligule a fringe of hairs (long). Contra-ligule present.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets.
Inflorescence. Inflorescence paniculate (large, plumose); open; with capillary branchlets; non-digitate (the branches more or less verticillate); espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes persistent. Spikelets not secund; pedicellate (with thin pedicels).
Female-fertile spikelets. Spikelets 5–9 mm long; compressed laterally; disarticulating above the glumes; disarticulating between the florets (somewhat below the lemmas). Rachilla prolonged beyond the uppermost female-fertile floret; hairy (but glabrous except above the abscission zone of each floret, the conspicuous hair tuft being on the callus); the rachilla extension with incomplete florets. Hairy callus present. The callus hairs white (long).
Glumes two; very unequal to more or less equal; shorter than the spikelets; shorter than the adjacent lemmas; hairless; pointed (acute to acuminate); awnless; carinate; similar. Lower glume 1–3 nerved. Upper glume 1–3 nerved. 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; sterile. The proximal lemmas awnless (acuminate, larger than but similar to the glumes); 3 nerved; exceeded by the female-fertile lemmas; similar in texture to the female-fertile lemmas; not becoming indurated.
Female-fertile florets 3–8. Lemmas similar in texture to the glumes (membranous); not becoming indurated; incised; 2 lobed; not deeply cleft (setaceously bidentate); awned (the distal florets with longer awns). Awns 1, or 3; median, or median and lateral (in that the lateral nerves may be excurrent into very short awns); the median similar in form to the laterals (when laterals present); from a sinus; non-geniculate; recurving; hairless; much shorter than the body of the lemma to about as long as the body of the lemma. The lateral awns when present, shorter than the median. Lemmas hairy (bearded marginally and on the lateral nerves); non-carinate (dorsally rounded); having the margins lying flat on the palea (hyaline); without a germination flap; 3 nerved. Palea present; relatively long; apically notched; awnless, without apical setae; not indurated; 2-nerved; 2-keeled. 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.
Fruit, embryo and seedling. Fruit free from both lemma and palea; small (1.5–2 mm long); linear; subteretete to angular. Hilum short. Pericarp fused. Embryo large; with an epiblast; with a scutellar tail; with an elongated mesocotyl internode. Embryonic leaf margins meeting.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells markedly different in shape costally and intercostally (the costals narrower and relatively longer); of similar wall thickness costally and intercostally. Mid-intercostal long-cells rectangular; and pitted. Microhairs absent. Stomata common; 18–21–22.5 microns long. Subsidiaries high dome-shaped (mostly), or triangular. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells common; in cork/silica-cell pairs (and a few solitary); silicified. Intercostal silica bodies present and perfectly developed; crescentic, saddle shaped, and oryzoid-type. Costal short-cells conspicuously in long rows (but many of the short-cells quite long). Costal silica bodies present in alternate cell files of the costal zones; rounded and 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 both abaxially and adaxially. PCR sheath extensions absent. Leaf blade with distinct, prominent adaxial ribs; with the ribs more or less constant in size. Midrib not readily distinguishable (its bundle somewhat larger); with one bundle only. Bulliforms present in discrete, regular adaxial groups; in simple fans and associated with colourless mesophyll cells to form deeply-penetrating fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present (with all the bundles); forming figures. Sclerenchyma not all bundle-associated. The extra sclerenchyma in abaxial groups; abaxial-hypodermal, the groups isolated (in small abaxial groups, opposite the bulliforms). The lamina margins with fibres.
Cytology. Chromosome base number, x = 10 (?). 2n = 40.
Classification. Watson & Dallwitz (1994): Chloridoideae; main chloridoid assemblage. Soreng et al. (2015): Chloridoideae; Triraphideae. 2 species.
Distribution, phytogeography, ecology. Tropical Africa, Madagascar, China, Indomalayan region.
Helophytic to mesophytic.
Rusts and smuts. Rusts Puccinia. Smuts from Ustilaginaceae. Ustilaginaceae Ustilago.
References, etc. Leaf anatomical: this project.
Illustrations. • N. reynaudiana: Hitchcock and Chase (1950). • N. arundinacea, as Arundo madagascariensis: Kunth (1835). • N. arundinacea, abaxial epidermis of leaf blade: this project. • N. arundinacea, abaxial epidermis of leaf blade detail: this project. • N. arundinacea, 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: 13th November 2017. delta-intkey.com/grass’.