The grass genera of the world
Type species: Type: E. monostachyos (Vahl) K.Schum. ex Engl.
Including Macrostachya A. Rich.
Habit, vegetative morphology. Perennial; caespitose. Culms 20–120 cm high; herbaceous; sparsely to amply branched above, or unbranched above. The branching simple. Culm nodes glabrous. Culm internodes solid, or hollow. Leaves mostly basal, or not basally aggregated; non-auriculate. Leaf blades linear; narrow; setaceous, or not setaceous; flat, or rolled (then involute-filiform); without abaxial multicellular glands; not pseudopetiolate; without cross venation; persistent; rolled in bud. Ligule a fringed membrane (short). Contra-ligule present, or absent.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets; with hidden cleistogenes (in E. chlorideus), or without hidden cleistogenes. The hidden cleistogenes of E. chlorideus subterranean.
Inflorescence. Inflorescence a single spike, or of spicate main branches, or a single raceme (with short pedicels); digitate, or subdigitate, or non-digitate (when consisting of a single raceme). Primary inflorescence branches 1–15. Inflorescence espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes persistent. Spikelets solitary; secund; biseriate; sessile to subsessile.
Female-fertile spikelets. Spikelets 5–8 mm long; adaxial; compressed dorsiventrally; disarticulating above the glumes; disarticulating between the florets. Rachilla prolonged beyond the uppermost female-fertile floret; the rachilla extension with incomplete florets. Hairy callus present. Callus short; blunt to pointed.
Glumes two (thin); very unequal; shorter than the spikelets, or about equalling the spikelets; (the longer) long relative to the adjacent lemmas; dorsiventral to the rachis; hairless; glabrous; awned (G2, often), or awnless; carinate; subulate to lanceolate, minutely bidentate, membranous or hyaline, divergent. Lower glume 1 nerved. Upper glume 1 nerved. Spikelets with incomplete florets. The incomplete florets distal to the female-fertile florets. The distal incomplete florets 1, or 2–4; merely underdeveloped, or clearly specialised and modified in form (sometimes represented by a cluster of awned rudiments); awned. Spikelets without proximal incomplete florets.
Female-fertile florets 1, or 2 (the L2 male or with a hermaphrodite floret). Lemmas decidedly firmer than the glumes (leathery, rigid); entire, or incised; when incised, 2 lobed; not deeply cleft (bidentate); awned. Awns 1; median; from a sinus, or apical; non-geniculate; about as long as the body of the lemma to much longer than the body of the lemma; entered by one vein, or entered by several veins (rarely, a pair of spikes). Lemmas hairless (glabrous or scaberulous); glabrous to scabrous; non-carinate (rounded to flat on the back); having the margins inrolled against the palea; 3 nerved (the median raised). Palea present; relatively long; entire to apically notched; awnless, without apical setae; not indurated (membranous or scarious); 2-nerved; 2-keeled. Lodicules present; 2; free; fleshy; glabrous. Stamens 3. Anthers not penicillate. Ovary apically glabrous. Styles free to their bases. Stigmas 2.
Fruit, embryo and seedling. Fruit small; ellipsoid; shallowly longitudinally grooved; compressed dorsiventrally (concavo-convex). Hilum short. Pericarp free (according to Clayton and Renvoize 1986), or fused. Embryo small to large (up to 1/3 of the grain length). Endosperm containing only simple starch grains.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae present; intercostal. Intercostal papillae over-arching the stomata; consisting of one symmetrical projection per cell, or consisting of one oblique swelling per cell. Long-cells similar in shape costally and intercostally; of similar wall thickness costally and intercostally. Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs present; elongated; clearly two-celled; chloridoid-type. Microhair apical cell wall of similar thickness/rigidity to that of the basal cell. Microhairs 21.6–24 microns long. Microhair basal cells 12–15 microns long. Microhairs (6–)9–11.4(–12) microns wide at the septum. Microhair total length/width at septum 1.8–4. Microhair apical cells 9.6–15 microns long. Microhair apical cell/total length ratio 0.43–0.63. Stomata common; about 15 microns long. Subsidiaries triangular. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells common, or absent or very rare; not paired (mainly solitary); not silicified. Intercostal silica bodies absent. Costal short-cells conspicuously in long rows, or neither distinctly grouped into long rows nor predominantly paired. Costal silica bodies present in alternate cell files of the costal zones; rounded (some), or saddle shaped (mainly), or crescentic.
Transverse section of leaf blade, physiology. Lamina mid-zone in transverse section open.
C4; XyMS+. PCR sheath outlines even. PCR sheaths of the primary vascular bundles interrupted; interrupted both abaxially and adaxially. PCR sheath extensions present, or absent. Maximum number of extension cells when present, 1–2. PCR cell chloroplasts centripetal. Mesophyll with radiate chlorenchyma; traversed by columns of colourless mesophyll cells, or not traversed by colourless columns. Leaf blade nodular in section, or adaxially flat; with the ribs more or less constant in size. Midrib conspicuous (rarely), or not readily distinguishable; with one bundle only, or having a conventional arc of bundles; with colourless mesophyll adaxially, or without colourless mesophyll adaxially. Bulliforms present in discrete, regular adaxial groups; in simple fans, or associated with colourless mesophyll cells to form deeply-penetrating fans (linked or not with traversing colourless columns). Many of the smallest vascular bundles unaccompanied by sclerenchyma, or all the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present; forming figures, or nowhere forming figures. Sclerenchyma all associated with vascular bundles. The lamina margins with fibres.
Phytochemistry. Leaves without flavonoid sulphates (2 species).
Cytology. Chromosome base number, x = 10. 2n = 20. 2 ploid.
Classification. Watson & Dallwitz (1994): Chloridoideae; main chloridoid assemblage. Soreng et al. (2015): Chloridoideae; Cynodonteae. 11 species.
Distribution, phytogeography, ecology. Africa, Seychelles, India, Formosa, Australia, Pacific.
Mesophytic to xerophytic; shade species, or species of open habitats; glycophytic. Savanna on sand or clay.
Economic aspects. Important native pasture species: E. acicularis, in arid/semiarid places; E. macrostachyus.
Rusts and smuts. Rusts Puccinia. Taxonomically wide-ranging species: Puccinia eritraeensis.
References, etc. Morphological/taxonomic: Jacobs and Highet 1988. Leaf anatomical: Metcalfe 1960; this project.
Illustrations. • E. macrostachyus: Gibbs Russell et al., 1990. • General aspect, ligule regions (E. dolichostachyus, E. minutus). • E. polygostachyus: E. Hickman. • Spikelet base, in situ (E. acicularis). • Spikelet of E. acicularis. • E. acicularis, spikelet details with glumes removed: this project. • Fruit of E. acicularis. • E. acicularis, abaxial epidermis of leaf blade: this project. • E. acicularis, abaxial epidermis of leaf blade: 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: 13th November 2017. delta-intkey.com/grass’.