The grass genera of the world
Habit, vegetative morphology. Annual; loosely caespitose (or culms single). Culms 40–75 cm high; herbaceous; unbranched above. Leaves not basally aggregated; non-auriculate. Leaf blades narrow; 2–9 mm wide (2.5–10 cm long); flat; without cross venation; persistent. Ligule present; a fringe of hairs.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. The spikelets all alike in sexuality.
Inflorescence. Inflorescence determinate; without pseudospikelets; of spicate main branches; non-digitate. Primary inflorescence branches 2–7. Inflorescence espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes persistent. Spikelets solitary; secund (the racemes dorsiventral); shortly pedicellate. Pedicel apices discoid.
Female-fertile spikelets. Spikelets 3.2–3.6 mm long; obovate; adaxial; compressed dorsiventrally; falling with the glumes; with a distinctly elongated rachilla internode between the glumes and with distinctly elongated rachilla internodes between the florets (the L2 being borne on a long, s-shaped stalk which straightens on maturity, and the glumes being slightly separated). The upper floret conspicuously stipitate. Rachilla terminated by a female-fertile floret; hairless. Hairy callus absent.
Glumes two; relatively large; more or less equal (G1 only slightly shorter, about 3/4 the length of the spikelet); long relative to the adjacent lemmas; dorsiventral to the rachis; hairy (G1 with glandular hairs, G2 with apical, rigid hairs); not pointed; awnless; non-carinate; very dissimilar (G1 membranous, glandular-hairy, G2 firmer and prominently net-veined). Lower glume 5 nerved. Upper glume not saccate; 5 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 reduced. The proximal incomplete florets male. The proximal lemmas reticulately veined, similar in form and texture to G2; awnless; 5 nerved; decidedly exceeding the female-fertile lemmas; less firm than the female-fertile lemmas; not becoming indurated.
Female-fertile florets 1 (very small relative to the rest of the spikelet). Lemmas decidedly firmer than the glumes; smooth (shiny); becoming indurated (crustaceous); entire; blunt; awnless; hairy (at the tip); non-carinate; having the margins inrolled against the palea; obscurely 5 nerved. Palea present; relatively long; entire (rounded at the tip); awnless, without apical setae; textured like the lemma (smooth); not indurated; 2-nerved. Lodicules present. Stamens 3. Ovary apically glabrous. Styles free to their bases. Stigmas 2.
Fruit, embryo and seedling. Fruit small (1.75 mm long); compressed dorsiventrally. Hilum short. Embryo large.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs present; panicoid-type; 33–39 microns long; 3.9–6.6 microns wide at the septum. Microhair total length/width at septum 5.5–10. Microhair apical cells 27–30 microns long. Microhair apical cell/total length ratio 0.75–0.82. Stomata common; 33–36 microns long. Subsidiaries low dome-shaped (mostly), or triangular. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells common; in cork/silica-cell pairs; silicified. Intercostal silica bodies cross-shaped. Costal short-cells predominantly paired (and a few short rows). Costal silica bodies panicoid-type; nearly all short dumb-bell shaped, or cross shaped.
Transverse section of leaf blade, physiology. C4; XyMS+. PCR sheath outlines uneven. Midrib not readily distinguishable (the main bundle slightly larger, with a somewhat heavier girder); with one bundle only, or having a conventional arc of bundles (if adjoining tiny bundles are counted as part of the midrib). Bulliforms the epidermis extensively bulliform. Many of the smallest vascular bundles unaccompanied by sclerenchyma. Combined sclerenchyma girders present (with the primaries); nowhere forming figures. Sclerenchyma all associated with vascular bundles.
Classification. Watson & Dallwitz (1994): Panicoideae; Panicodae; Paniceae. Soreng et al. (2015): Panicoideae; Panicodae; Paniceae; Melidininae. 1 species (E. obconiciventris).
Distribution, phytogeography, ecology. Tropical Africa.
Species of open habitats. Savanna.
References, etc. Morphological/taxonomic: Launert 1965. Leaf anatomical: studied by us.
Illustrations. • E. obconiciventris: Clayton, Flora Zambesiaca 10 (1989)
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. delta-intkey.com/grass’.