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The grass genera of the world

L. Watson, T.D. Macfarlane, and M.J. Dallwitz

Zizania L.

From the Greek Zizanion, ancient Greek for a weed of grain.

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)


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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: 14th June 2017. delta-intkey.com/grass’.

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