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The grass genera of the world

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

Eremopogon Stapf

~ Dichanthium

Habit, vegetative morphology. Annual (rarely), or perennial; caespitose. Culms herbaceous; branched above. Leaves non-auriculate. Leaf blades without cross venation. Ligule present.

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, or hermaphrodite and sterile; overtly heteromorphic (the pedicellate members awnless); all in heterogamous combinations.

Inflorescence. Inflorescence of ‘racemes’, each branch with a basal bladeless sheath and a terminal ‘raceme’; spatheate; a complex of ‘partial inflorescences’ and intervening foliar organs. Spikelet-bearing axes ‘racemes’; solitary; with very slender rachides; disarticulating; disarticulating at the joints. ‘Articles’ linear; not appendaged; disarticulating transversely. Spikelets paired; sessile and pedicellate; consistently in ‘long-and-short’ combinations; in pedicellate/sessile combinations. Pedicels of the ‘pedicellate’ spikelets free of the rachis. The ‘shorter’ spikelets hermaphrodite. The ‘longer’ spikelets male-only, or sterile.

Female-sterile spikelets. 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; more or less equal; long relative to the adjacent lemmas; awnless; very dissimilar (the lower bicarinate, the upper naviculate). Lower glume two-keeled (the keels not winged); with a conspicuous pit; relatively smooth. Upper glume 2 nerved. Spikelets with incomplete florets. The incomplete florets proximal to the female-fertile florets. Spikelets with proximal incomplete florets. The proximal incomplete florets 1; epaleate; sterile. The proximal lemmas awnless; 0 nerved; not becoming indurated (hyaline).

Female-fertile florets 1. Lemmas reduced to a linear stipe beneath the awn; less firm than the glumes; entire, or incised (sometimes); sometimes 2 lobed (bidentate); awned. Awns 1; median; from a sinus, or apical; geniculate; hairless (glabrous); much longer than the body of the lemma. Lemmas hairless; 0–1 nerved. Palea absent. Lodicules present; 2. Stamens 3. Ovary apically glabrous. Styles free to their bases. Stigmas 2.

Fruit, embryo and seedling. Hilum short. Embryo large.

Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous (on focusing through the overlying papillae). Papillae present. Intercostal papillae over-arching the stomata (and obscuring all else in high focus); consisting of one symmetrical projection per cell (unusually large, bulbous, overlapping one another as well as the stomata). Long-cells similar in shape costally and intercostally; of similar wall thickness costally and intercostally (thin walled). Mid-intercostal long-cells rectangular; having markedly sinuous walls (but the sinuosity very small scale). Microhairs present; panicoid-type; 51–66 microns long; 6.9–9 microns wide at the septum. Microhair total length/width at septum 5.7–8.6. Microhair apical cells 27–39 microns long. Microhair apical cell/total length ratio 0.53–0.6. Stomata common; 27–30 microns long. Subsidiaries dome-shaped and triangular. Guard-cells with the guard-cell insertion obscured. Intercostal short-cells absent or very rare. A few small prickles present. Costal short-cells conspicuously in long rows. Costal silica bodies ‘panicoid-type’.

Transverse section of leaf blade, physiology. C4; XyMS–. Mesophyll with radiate chlorenchyma. Leaf blade adaxially flat. Midrib conspicuous (via an abaxial keel and the conspicuous sclerenchyma group beneath its main bundle); with one bundle only to having a conventional arc of bundles (the large bundle flanked on either side by one or two small ones, these arguably within the limits of the midrib); without colourless mesophyll adaxially (though there appear to be one or two colourless cells adjoining the adaxial sclerenchyma of the main bundle). Bulliforms not present in discrete, regular adaxial groups (the entire epidermis being ‘bulliform’, all its cells tanniniferous except over the midrib). Many of the smallest vascular bundles unaccompanied by sclerenchyma. Combined sclerenchyma girders present (with all the primaries); forming ‘figures’ (the midrib with an anchor). Sclerenchyma all associated with vascular bundles.

Cytology. Chromosome base number, x = 10. 2n = 40. 4 ploid.

Classification. Watson & Dallwitz (1994): Panicoideae; Andropogonodae; Andropogoneae; Andropogoninae. Soreng et al. (2015): Panicoideae; Andropogonodae; Andropogoneae; Anthistiriinae (?). 4 species.

Distribution, phytogeography, ecology. Warm Old World.

Rusts and smuts. Rusts — Puccinia. Taxonomically wide-ranging species: ‘Uromycesclignyi. Smuts from Ustilaginaceae. Ustilaginaceae — Sphacelotheca and Ustilago.

References, etc. Leaf anatomical: studied by us - E. foveolatus (Del.) Stapf.

Illustrations. • E. foveolatus: Jacques-Félix, 1962

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.’.