The grass genera of the world
Habit, vegetative morphology. Slender, erect, rigid annual. Culms 20–40 cm high; herbaceous. Leaves non-auriculate. Leaf blades linear; narrow; flat, or rolled (convolute when dry); without cross venation. Ligule an unfringed membrane; truncate; 0.7 mm long.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. The spikelets all alike in sexuality.
Inflorescence. Inflorescence unilateral, a single spike, or a single raceme (the pedicels to 0.5 mm long), or paniculate (with few branches below); rigid, the spikelets appressed, set in depressions in the rachis. Rachides hollowed. Spikelets all partially embedded in the rachis. Inflorescence espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes persistent. Spikelets solitary; secund; distichous; subsessile (the pedicels no more than 0.5 mm long).
Female-fertile spikelets. Spikelets 3–7 mm long; compressed laterally; disarticulating above the glumes; disarticulating between the florets. Rachilla prolonged beyond the uppermost female-fertile floret; the rachilla extension naked. Hairy callus absent.
Glumes two; more or less equal; long relative to the adjacent lemmas; dorsiventral to the rachis; not pointed (broadly rounded to emarginate); awnless; non-carinate; similar (with a prominent midrib). Lower glume 1–5 nerved. Upper glume 3–5 nerved. Spikelets with female-fertile florets only.
Female-fertile florets 4–6. Lemmas similar in texture to the glumes (papery, the margins hyaline); not becoming indurated; entire to incised (emarginate to shortly bifid, sometimes apiculate); when incised, 2 lobed; not deeply cleft; awnless; hairless; glabrous; non-carinate (to very slightly so); without a germination flap; 5 nerved. Palea present; relatively long; apically notched (shortly 2-fid); 2-nerved; 2-keeled. Lodicules present; 2; free; membranous; glabrous; toothed; not or scarcely vascularized. Stamens 3. Ovary apically glabrous. Styles free to their bases. Stigmas 2.
Fruit, embryo and seedling. Fruit adhering to lemma and/or palea (slightly, to the palea); small (1–1.8 mm long); not noticeably compressed. Hilum short. Embryo small. Endosperm hard; without lipid; containing compound starch grains. Embryo with an epiblast; without a scutellar tail; with a negligible mesocotyl internode. Embryonic leaf margins meeting.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae present to absent (the cuticle seeming to undulate with reference to the lateral sinuations, in places forming low, oblique papillae). Long-cells markedly different in shape costally and intercostally (the costals much smaller and narrower); of similar wall thickness costally and intercostally (fairly thick walled). Mid-intercostal long-cells rectangular (quite regular); having markedly sinuous walls (the sinuosity coarse, associated with conspicuous pitting). Microhairs absent. Stomata absent or very rare. Intercostal short-cells absent or very rare (very few); in cork/silica-cell pairs (a few pairs seen); silicified. Costal short-cells neither distinctly grouped into long rows nor predominantly paired (mostly in pairs and short rows). Costal silica bodies present and well developed; horizontally-elongated crenate/sinuous and horizontally-elongated smooth, or rounded (many of these being more or less irregular).
Transverse section of leaf blade, physiology. C3; XyMS+. Leaf blade with distinct, prominent adaxial ribs. Midrib fairly conspicuous (with a large, flat topped adaxial rib and an adaxial strand); with one bundle only. The lamina symmetrical on either side of the midrib. Bulliforms present in discrete, regular adaxial groups, or not present in discrete, regular adaxial groups (? - not apparent in the poor material seen); if present, in simple fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders absent (all the bundles with small abaxial strands, apart from the midrib with its adaxial strand as well). Sclerenchyma all associated with vascular bundles.
Cytology. Chromosome base number, x = 7. 2n = 14. 2 ploid.
Classification. Watson & Dallwitz (1994): Pooideae; Poodae; Poeae. Soreng et al. (2015): Pooideae; Poodae; Poeae; Loliinae. 1 species (N. salzmannii).
Distribution, phytogeography, ecology. Mediterranean.
References, etc. Leaf anatomical: studied by us.
Illustrations. • N. salzmanni: adapted from Boissier (1839), Voyage botanique dans le midi de l’Espagne.
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’.