The grass genera of the world
Including Ceratochaete Lunell, Elymus Mitchell, Fartis Adans., Hydropyrum Link, Melinum Link
Habit, vegetative morphology. Tall, aquatic annual, or perennial. Culms 100–300 cm high; herbaceous. Culm nodes hairy, or glabrous. Culm internodes hollow. Leaves non-auriculate. Leaf blades linear-lanceolate; broad (to 3 cm), or narrow; 5–30 mm wide; flat; pseudopetiolate, or not pseudopetiolate; without cross venation (?). Ligule an unfringed membrane; 3–11 mm long.
Reproductive organization. Plants monoecious with all the fertile spikelets unisexual; without hermaphrodite florets. The spikelets of sexually distinct forms on the same plant; female-only and male-only. The male and female-fertile spikelets on different branches of the same inflorescence (the lower, pendent branches male, the upper, ascending ones female). Plants inbreeding.
Inflorescence. Inflorescence paniculate (large, terminal); open; espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes persistent. Spikelets not secund; pedicellate.
Female-sterile spikelets. Male spikelets pendent, lemmas membranous, acute or short-awned, 5-nerved; palea 3-nerved; 6 free stamens. The male spikelets without glumes; 1 floreted. The lemmas awnless to awned. Male florets 6 staminate. The staminal filaments free.
Female-fertile spikelets. Spikelets unconventional (the glumes obsolete); 10–25 mm long (ascending); lanceolate; compressed laterally to not noticeably compressed; falling entire. Rachilla terminated by a female-fertile floret. Hairy callus absent.
Glumes absent (but perhaps represented by a small collar-like ridge on the pedicel). Spikelets with female-fertile florets only.
Female-fertile florets 1. Lemmas acuminate into the long, acuminate lemma; not becoming indurated (papery); entire; pointed; awned. Awns 1; median; apical (from the into a long, slender awn); non-geniculate; about as long as the body of the lemma to much longer than the body of the lemma. Lemmas non-carinate; 3–5 nerved. Palea present; relatively long; 2-nerved; one-keeled. Stamens 0. Ovary apically glabrous. Styles free to their bases. Stigmas 2.
Fruit, embryo and seedling. Fruit medium sized, or large (10–20 mm long); not noticeably compressed (cylindrical). Hilum long-linear. Endosperm hard; without lipid. Embryo with an epiblast; with a scutellar tail; with a negligible mesocotyl internode. Embryonic leaf margins overlapping.
Seedling with a long mesocotyl; with a loose coleoptile (margins free, lamina well developed).
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae present. Intercostal papillae over-arching the stomata; several per cell (each long-cell with one large and many small papillae). Mid-intercostal long-cells having markedly sinuous walls (the walls thin). Microhairs present; panicoid-type (tapering to base and apex); 26–36 microns long. Microhair apical cells 14–18 microns long. Microhair apical cell/total length ratio 0.48. Stomata common. Subsidiaries triangular. Intercostal short-cells common; in cork/silica-cell pairs; silicified. Intercostal silica bodies narrowly oryzoid-type, or vertically elongated-nodular. Costal zones with short-cells. Costal short-cells predominantly paired, or neither distinctly grouped into long rows nor predominantly paired. Costal silica bodies oryzoid; not sharp-pointed.
Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with non-radiate chlorenchyma; with arm cells; with fusoids. The fusoids external to the PBS. Midrib conspicuous (with a characteristic system of intercellular spaces); having complex vascularization. Bulliforms present in discrete, regular adaxial groups; in simple fans, or associated with colourless mesophyll cells to form deeply-penetrating fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present.
Cytology. Chromosome base number, x = 15. 2n = 30 and 34. 2 ploid. Chromosomes small. Haploid nuclear DNA content 2.2 pg (1 species). Mean diploid 2c DNA value 4.4 pg (Z. aquatica).
Classification. Watson & Dallwitz (1994): Bambusoideae; Oryzodae; Oryzeae. Soreng et al. (2015): Oryzoideae; Oryzeae; Zizaniinae. 3 species.
Distribution, phytogeography, ecology. North America and Eurasia.
Hydrophytic to helophytic.
Economic aspects. Grain crop species: breeding of Zizania aquatica (Wildrice, long gathered from wild stands) is yielding non-shattering forms of potential economic value. Z. latifolia cultivated for its edible young shoots.
Rusts and smuts. Smuts from Tilletiaceae and from Ustilaginaceae. Tilletiaceae Entyloma. Ustilaginaceae Ustilago.
References, etc. Leaf anatomical: Metcalfe 1960 and this project.
Illustrations. • Z. aquatica: P. Beauv. (1812). • Z. aquatica: Hitchcock and Chase (1950)
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: 12th March 2017. delta-intkey.com/grass’.