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The grass genera of the world

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

Elionurus Humb. & Bonpl.

From the Greek eleuin (to bend, curve) and oura (tail), alluding to curved, cylindric inflorescences.

Including Callichloea Steud., Habrurus Hochst.

Habit, vegetative morphology. Annual, or perennial; caespitose. Culms 10–150 cm high; herbaceous; branched above, or unbranched above. The branching simple. Culm nodes glabrous. Culm internodes solid. The shoots aromatic (with a bitter taste), or not aromatic. Leaves not basally aggregated; non-auriculate. Leaf blades narrow; setaceous, or not setaceous; sometimes flat, or folded (tightly); without cross venation; persistent. Ligule a fringed membrane (very short), or a fringe of hairs.

Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. The spikelets of sexually distinct forms on the same plant; hermaphrodite and male-only; homomorphic; all in heterogamous combinations.

Inflorescence. Inflorescence a single raceme, or paniculate (of single ‘racemes’, terminal or sometimes axillary and gathered into false panicles). Rachides flattened. Inflorescence spatheate; a complex of ‘partial inflorescences’ and intervening foliar organs, or not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes spikelike (flexuous); solitary; with substantial rachides (these flattened); disarticulating; disarticulating at the joints. ‘Articles’ linear, or non-linear; appendaged (with a scarious lobe, in E. elegans and relatives), or not appendaged; disarticulating obliquely; densely long-hairy. Spikelets paired; secund (all the sessile spikelets on one side); sessile and pedicellate; consistently in ‘long-and-short’ combinations; in pedicellate/sessile combinations. Pedicels of the ‘pedicellate’ spikelets free of the rachis (resembling the internode). The ‘shorter’ spikelets hermaphrodite. The ‘longer’ spikelets male-only.

Female-sterile spikelets. The pedicelled, male spikelets well developed, muticous or aristulate. The male spikelets with glumes; 2 floreted. The lemmas awnless.

Female-fertile spikelets. Spikelets compressed dorsiventrally; falling with the glumes. Rachilla terminated by a female-fertile floret. Hairy callus present.

Glumes two; relatively large; very unequal to more or less equal; (the longer) long relative to the adjacent lemmas; hairy, or hairless; with distinct hair tufts, or with distinct rows of hairs; awned (the G1 often cuspidate to a bifid tip, with tails several mm long), or awnless; very dissimilar (the lower tougher, carinate on the edges, its keels generally glandular or with tufts of hairs, the upper membranous, lanceolate, not 2-keeled), or similar (rarely, then both subulate). Lower glume two-keeled (keels not winged, but often ciliate and bordered by a dense oil streak); convex on the back to flattened on the back; not pitted; relatively smooth, or tuberculate (then with ciliate or hair-tufted tubercles on the keels); 9 nerved. Upper glume 3 nerved. Spikelets with incomplete florets. The incomplete florets proximal to the female-fertile florets. The proximal incomplete florets 1; epaleate; sterile. The proximal lemmas awnless; decidedly exceeding the female-fertile lemmas; similar in texture to the female-fertile lemmas (hyaline); not becoming indurated.

Female-fertile florets 1. Lemmas less firm than the glumes (hyaline); not becoming indurated; entire; awnless; 0 nerved. Palea present, or absent; when present, very reduced; not indurated; nerveless. Lodicules present; 2; free; fleshy; glabrous. Stamens 3. Anthers not penicillate. Ovary apically glabrous. Styles free to their bases. Stigmas 2; red pigmented.

Fruit, embryo and seedling. Fruit free from both lemma and palea; small; compressed dorsiventrally. Hilum short. Embryo large; waisted. Endosperm hard; without lipid.

Abaxial leaf blade epidermis. Papillae absent. Mid-intercostal long-cells having markedly sinuous walls. Microhairs present; panicoid-type; 45–80 microns long. Microhair apical cells 22–51 microns long. Microhair apical cell/total length ratio 0.53–0.6. Stomata common. Subsidiaries tall dome-shaped, or triangular. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells common, or absent or very rare; when present, in cork/silica-cell pairs, or in cork/silica-cell pairs and not paired; silicified. Intercostal silica bodies when present, rounded, or crescentic, or tall-and-narrow. Costal short-cells predominantly paired. Costal silica bodies tall-and-narrow, or ‘panicoid-type’; cross shaped, or butterfly shaped, or dumb-bell shaped, or nodular; sharp-pointed.

Transverse section of leaf blade, physiology. C4; XyMS–. PCR cell chloroplasts centrifugal/peripheral. Mesophyll with radiate chlorenchyma. Leaf blade ‘nodular’ in section; with the ribs more or less constant in size. Midrib conspicuous (sometimes with an adaxial bulliform group); having a conventional arc of bundles; with colourless mesophyll adaxially (the colourless tissue sometimes extending across the lamina adaxially). Bulliforms not present in discrete, regular adaxial groups (in irregular groups, the epidermis extensively bulliform). Many of the smallest vascular bundles unaccompanied by sclerenchyma. Combined sclerenchyma girders present; forming ‘figures’ (rarely), or nowhere forming ‘figures’. Sclerenchyma all associated with vascular bundles.

Phytochemistry. Leaves without flavonoid sulphates (2 species).

Cytology. Chromosome base number, x = 5 and 10. 2n = 10 and 20.

Classification. Watson & Dallwitz (1994): Panicoideae; Andropogonodae; Andropogoneae; Rottboelliinae. Soreng et al. (2015): Panicoideae; Andropogonodae; Andropogoneae; Rottboelliinae. 15 species.

Distribution, phytogeography, ecology. Tropical and subtropical.

Mesophytic to xerophytic; species of open habitats; glycophytic. Savanna, often on dry soils.

Economic aspects. Important native pasture species: several, especially in tropical America and Africa (e.g. E. royleanus, E. tripsacoides).

Rusts and smuts. Smuts from Ustilaginaceae. Ustilaginaceae — Sphacelotheca and Ustilago.

References, etc. Leaf anatomical: Metcalfe 1960; studied by us - E. citreus (R. Br.) Munro ex Benth.

Illustrations. • E. elegans: Kunth (1835). • E. ciliaris, as E. pobeguinii: Rose Innes, Ghana Grasses (1977). • E. muticus: Gibbs Russell et al., 1990. • E. citreus, leaf blade TS: this project

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.’.