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The grass genera of the world

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

Echinochloa P. Beauv.

From the Greek echinos (hedgehog) and chloa (grass), alluding to the echinate inflorescence branches.

Type species: Type: E. crus-galli (L.) P.Beauv.

Including Ornithospermum Dumoulin, Tema Adans.

Habit, vegetative morphology. Annual, or perennial; caespitose to decumbent (or floating). Culms 40–360 cm high; herbaceous; sometimes floating; sparsely branched above, or unbranched above. The branching simple. Culms tuberous, or not tuberous. Culm nodes glabrous. Culm leaf sheaths keeled, or compressed, or rounded. Culm internodes solid, or hollow. Leaves not basally aggregated; non-auriculate. Leaf blades broad; flat; without cross venation; persistent; rolled in bud. Ligule present, or absent; when present, a fringe of hairs. Contra-ligule present (of hairs), or absent.

Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. The spikelets all alike in sexuality. Plants outbreeding and inbreeding; exposed-cleistogamous, or chasmogamous.

Inflorescence. Inflorescence of spicate main branches (the spikelets often hispid). Primary inflorescence branches borne biseriately on one side of the main axis, or inserted all around the main axis. Inflorescence espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets paired, or clustered in little secondary racemelets; secund; typically and characteristically in four dense rows, but occasionally in two; shortly pedicellate, or subsessile. Pedicel apices oblique, or truncate, or discoid, or cupuliform. Spikelets imbricate.

Female-fertile spikelets. Spikelets 2.3–7 mm long; elliptic, or lanceolate, or ovate; adaxial (probably best interpreted as adaxial relative to the reduced, spikelet-bearing branch); compressed dorsiventrally; planoconvex; falling with the glumes. Rachilla terminated by a female-fertile floret. Hairy callus absent.

Glumes two; very unequal; (the upper) shorter than the adjacent lemmas to long relative to the adjacent lemmas; dorsiventral to the rachis; pointed; awned, or awnless; with the keel conspicuously winged, or without a median keel-wing; very dissimilar (the G1 usually much shorter, ovate, often mucronate, the G2 strongly concave, acute, cuspidate or awned). Lower glume 0–3 nerved. Upper glume 5 nerved, or 7 nerved. Spikelets with incomplete florets. The incomplete florets proximal to the female-fertile florets. Spikelets with proximal incomplete florets. The proximal incomplete florets 1; paleate. Palea of the proximal incomplete florets fully developed, or reduced (e.g. E. kimberleyensis). The proximal incomplete florets male (rarely), or sterile. The proximal lemmas similar to the G2 but flattened on the back, often with a large cusp or awned; awned, or awnless; 5 nerved; less firm than the female-fertile lemmas to similar in texture to the female-fertile lemmas; not becoming indurated.

Female-fertile florets 1. Lemmas usually blunt-apiculate, with a laterally compressed, incurved beak; decidedly firmer than the glumes; smooth; becoming indurated to not becoming indurated (subleathery to crustaceous); yellow in fruit; entire; awnless (obtuse to apiculate); hairless (shiny); non-carinate; having the margins inrolled against the palea; with a clear germination flap; 5 nerved. Palea present (the tip reflexed); relatively long; entire; awnless, without apical setae; textured like the lemma; indurated, or not indurated; 2-nerved. Lodicules present; joined, or free; fleshy; glabrous. Stamens 3. Anthers 0.4–1.2 mm long; not penicillate. Ovary apically glabrous. Styles free to their bases. Stigmas 2; red pigmented.

Fruit, embryo and seedling. Fruit small; compressed dorsiventrally. Hilum short. Embryo large; waisted, or not waisted. Endosperm hard; without lipid; containing only simple starch grains. Embryo without an epiblast; with a scutellar tail; with an elongated mesocotyl internode. Embryonic leaf margins overlapping.

Seedling with a long mesocotyl; with a loose coleoptile. First seedling leaf with a well-developed lamina. The lamina broad; curved; 13–20 veined (?).

Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae present. Intercostal papillae over-arching the stomata, or not over-arching the stomata; consisting of one oblique swelling per cell. Long-cells similar in shape costally and intercostally to markedly different in shape costally and intercostally (the costals narrower); of similar wall thickness costally and intercostally. Mid-intercostal long-cells rectangular; having markedly sinuous walls, or having straight or only gently undulating walls. Microhairs present; panicoid-type; 36–60 microns long; 6–6.6 microns wide at the septum. Microhair total length/width at septum 7.3–9. Microhair apical cells (16–)22–30 microns long. Microhair apical cell/total length ratio 0.48–0.57. Stomata common; 39–46.5 microns long. Subsidiaries low dome-shaped, or triangular. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells absent or very rare; in cork/silica-cell pairs, or not paired; silicified (when paired), or not silicified. Intercostal silica bodies when present, cross-shaped. Costal short-cells conspicuously in long rows. Costal silica bodies ‘panicoid-type’; cross shaped to nodular.

Transverse section of leaf blade, physiology. C4; biochemical type NADP–ME (3 species); XyMS–. PCR sheath outlines uneven. PCR sheath extensions absent. PCR cell chloroplasts with reduced grana; centrifugal/peripheral. Mesophyll with radiate chlorenchyma. Leaf blade with distinct, prominent adaxial ribs, or adaxially flat; with the ribs more or less constant in size. Midrib conspicuous; having a conventional arc of bundles; with colourless mesophyll adaxially. Bulliforms not present in discrete, regular adaxial groups (mostly in irregular groups, or the epidermis extensively bulliform); sometimes, irregularly in simple fans. Many of the smallest vascular bundles unaccompanied by sclerenchyma. Combined sclerenchyma girders absent. Sclerenchyma all associated with vascular bundles.

Culm anatomy. Culm internode bundles in one or two rings.

Phytochemistry. Tissues of the culm bases with abundant starch. Leaves without flavonoid sulphates (2 species).

Special diagnostic feature. Glumes and/or sterile lemmas awned or acuminate-mucronate.

Cytology. Chromosome base number, x = 9. 2n = 27, 36, 42, 48, 54, 72, and 108. Chromosomes ‘small’. Mean diploid 2c DNA value 2.7 pg (?-E. frumentacea, ploidy unknown).

Classification. Watson & Dallwitz (1994): Panicoideae; Panicodae; Paniceae. Soreng et al. (2015): Panicoideae; Panicodae; Paniceae; Boivinellinae. 30–40 species.

Distribution, phytogeography, ecology. In warm regions.

Commonly adventive. Hydrophytic, helophytic, and mesophytic; mostly species of open habitats; glycophytic. In water and moist or marshy places, also in disturbed ground and weedy places.

Economic aspects. Significant weed species: E. oryzoides and E. stagnina (in rice), E. crusgalli (especially in arable land), E. colonum, E. crus-pavonis, E. pyramidalis. Cultivated fodder: E. frumentacea, E. stagnina. Important native pasture species: all more or less palatable to stock. Grain crop species: minor cereals: E. frumentacea (Sawa - India), E. utilis (China and Japan), E. colona (Shama millet), E. pyramidalis.

Rusts and smuts. Rusts — Puccinia. Smuts from Tilletiaceae and from Ustilaginaceae. Tilletiaceae — Entyloma and Tilletia. Ustilaginaceae — Sorosporium, Sphacelotheca, Tolyposporium, and Ustilago.

References, etc. Leaf anatomical: Metcalfe 1960; studied by us - E. colona (L.) Link, E. crus-galli (L.) Beauv.

Illustrations. • E. colona: Gardner, 1952. • E. crus-galli: P. Beauv. (1812). • E. crus-galli: Gibbs Russell et al., 1990. • E. crus-galli: Eng. Bot. (1872). • E. crus-pavonis, as Panicum: Wood, Natal Plants 2 (1904). • Ligule region (E. crus-galli). • Ligule region (E. crus-galli). Echinochloa crus-galli. Upper culm leaf, lacking ligule. • Inflorescence detail (E. crus-galli). • Inflorescence detail (E. crus-galli). • Inflorescence detail (E. colona). • Opened spikelet (E. crus-galli). Echinochloa crus-galli. Smooth, shining back of female-fertile lemma. • Germinating E. crus-galli. Echinochloa crus-galli. Radicle emerging via raised germination flap. • E. kimberleyensis, abaxial epidermis of leaf blade: this project. • E. crus-galli, abaxial epidermis of leaf blade: this project. • E. crus-galli, abaxial epidermis of leaf blade: this project. • E. crus-galli, abaxial epidermis of leaf blade: this project. • E. cris-galli, T.S. leaf blade midrib zone: this project. • E. crus-galli, TS leaf blade: this project. • Pollen antigens: Watson and Knox (1976)

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.’.