The grass genera of the world
Habit, vegetative morphology. Perennial; stoloniferous, or decumbent. Culms 5–70 cm high; herbaceous. Culm nodes glabrous. Culm internodes hollow. Leaves non-auriculate. Sheath margins joined. Leaf blades linear; narrow; to 3–10 mm wide; flat; without cross venation; persistent; once-folded in bud. Ligule an unfringed membrane; not truncate; 2–8 mm long.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets.
Inflorescence. Inflorescence paniculate; with capillary branchlets; espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes persistent. Spikelets not secund; pedicellate.
Female-fertile spikelets. Spikelets 1.5–5 mm long; compressed laterally; disarticulating above the glumes. Rachilla prolonged beyond the uppermost female-fertile floret; hairless; the rachilla extension with incomplete florets, or naked. Hairy callus absent. Callus short (glabrous).
Glumes two; very unequal; shorter than the spikelets; shorter than the adjacent lemmas (the longer, upper glume less than 2/3 its length); free; not pointed (obtuse to truncate); awnless; non-carinate; similar (broad). Lower glume much shorter than half length of lowest lemma (less than 1/3 its length); 0–1 nerved. Upper glume 1–3 nerved. Spikelets with female-fertile florets only, or with incomplete florets. The incomplete florets if present, distal to the female-fertile florets. The distal incomplete florets merely underdeveloped.
Female-fertile florets (1–)2(–3). Lemmas decidedly firmer than the glumes (thinly membranous, with hyaline tips); not becoming indurated; entire (erose); blunt (obtuse to truncate); awnless; hairless; non-carinate; without a germination flap; prominently 3 nerved (these raised). Palea present; relatively long; awnless, without apical setae; not indurated (scarious); 2-nerved; 2-keeled. Lodicules present; 2; free; membranous; glabrous. Stamens 3. Anthers 0.7–1.8 mm long; not penicillate. Ovary apically glabrous. Styles free to their bases. Stigmas 2.
Fruit, embryo and seedling. Fruit free from both lemma and palea; small; compressed laterally. Hilum short. Embryo small; not waisted. Endosperm hard; without lipid. Embryo with an epiblast; without a scutellar tail; with a negligible mesocotyl internode. Embryonic leaf margins meeting.
Seedling with a tight coleoptile. First seedling leaf with a well-developed lamina. The lamina narrow; 3–4 veined.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae present; costal and intercostal. Intercostal papillae over-arching the stomata (at one end); consisting of one oblique swelling per cell. Long-cells differing markedly in wall thickness costally and intercostally (the costals quite thick walled). Mid-intercostal long-cells rectangular and fusiform; having straight or only gently undulating walls. Microhairs absent. Stomata common; 22.5–24 microns long. Subsidiaries non-papillate; consistently parallel-sided. Guard-cells overlapped by the interstomatals. Intercostal short-cells common; not paired (solitary); not silicified. Costal short-cells neither distinctly grouped into long rows nor predominantly paired (mostly solitary). Costal silica bodies absent (in the material seen).
Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with non-radiate chlorenchyma; without adaxial palisade. Leaf blade adaxially flat. Midrib conspicuous (via an abaxial keel, and constrictions of the lamina on either side); with one bundle only. Bulliforms not present in discrete, regular adaxial groups (apart from midrib hinges). All the vascular bundles accompanied by sclerenchyma (though all but the primaries are depauperate in sclerenchyma). Combined sclerenchyma girders absent (even the major bundles have only small adaxial and abaxial strands). Sclerenchyma all associated with vascular bundles (apart from conspicuous groups at the blade margins).
Cytology. Chromosome base number, x = 5. 2n = 10 and 20. 2 and 4 ploid. Chromosomes large.
Classification. Watson & Dallwitz (1994): Pooideae; Poodae; Meliceae. Soreng et al. (2015): Pooideae; Poodae; Poeae; Coleanthinae. 2 species.
Distribution, phytogeography, ecology. North temperate.
Helophytic to mesophytic; species of open habitats; glycophytic. In marshes and shallow water.
Rusts and smuts. Rusts Puccinia. Taxonomically wide-ranging species: Puccinia graminis, Puccinia coronata, Puccinia striiformis, and Puccinia brachypodii. Smuts from Tilletiaceae and from Ustilaginaceae. Tilletiaceae Entyloma. Ustilaginaceae Ustilago.
References, etc. Leaf anatomical: Metcalfe 1960 and this project.
Illustrations. • C. aquatica: P. Beauv. (1812). • C. aquatica, general aspect: Eng. Bot. (1872). • C. aquatica, general aspect: J. Curtis, 1824
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’.