The grass genera of the world
Type species: Type: E. articulatus P. Beauv. = E. spicatus (Willd.) A.Camus.
Including Echinalysium Trin.
Habit, vegetative morphology. Annual; caespitose. Culms 10–50 cm high; herbaceous. Culm nodes glabrous. Culm internodes solid. Leaves not basally aggregated; non-auriculate. Leaf blades linear; narrow; flat; without abaxial multicellular glands; without cross venation; persistent; rolled in bud. Ligule an unfringed membrane to a fringed membrane.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. The spikelets of sexually distinct forms on the same plant; hermaphrodite, or hermaphrodite and sterile (reduced, sterile spikelets often present at the bases of the spikelet clusters).
Inflorescence. Inflorescence a false spike, with spikelets on contracted axes (the glomerules sometimes confluent to form a cylinder); espatheate (but the glomerules and the clusters within them subtended by the enlarged, spreading glumes of the lower spikelets); not comprising partial inflorescences and foliar organs. Spikelet-bearing axes very much reduced (to glomerules); persistent. Spikelets associated with bractiform involucres (these constituted by the enlarged glumes of the lower spikelets); not secund.
Female-fertile spikelets. Spikelets strongly compressed laterally; disarticulating above the glumes; disarticulating between the florets; with conventional internode spacings. Rachilla prolonged beyond the uppermost female-fertile floret; the rachilla extension with incomplete florets. Hairy callus absent.
Glumes two; more or less equal; shorter than the spikelets, or about equalling the spikelets; long relative to the adjacent lemmas; hairy (sparsely hispid on the margins); pointed (acuminate); awned (shortly aristulate), or awnless (muticous); carinate; similar (narrowly lanceolate, persistent, membranous). Lower glume 1 nerved. Upper glume 1 nerved. Spikelets with incomplete florets. The incomplete florets distal to the female-fertile florets.
Female-fertile florets 2–7. Lemmas drawn out into the awn; similar in texture to the glumes (membranous, granular, ovate); not becoming indurated; entire; pointed; awned. Awns 1; median; apical (lemma becoming setaceous at the summit); non-geniculate; much shorter than the body of the lemma; entered by one vein. Lemmas hairless (or scabrid ciliate on the keel and margins); carinate (naviculate); 3 nerved. Palea present; conspicuous but relatively short; deeply bifid; awnless, without apical setae; not indurated (hyaline); 2-nerved (or more?); 2-keeled. Palea keels winged (the wings narrow or broad, dorsal). Lodicules present; 1, or 2; free; fleshy; glabrous; not toothed. Stamens 1–3. Anthers 0.5 mm long; not penicillate. Ovary apically glabrous. Styles fused, or free to their bases. Stigmas 2.
Fruit, embryo and seedling. Fruit free from both lemma and palea; small; not noticeably compressed. Hilum short. Pericarp free. Embryo large (half the fruit length); not waisted. Endosperm containing compound starch grains. Embryo without an epiblast; with a scutellar tail; with an elongated mesocotyl internode. Embryonic leaf margins meeting.
First seedling leaf with a well-developed lamina. The lamina narrow; erect.
Ovule, embryology. Micropyle oblique. Outer integument extensive, being absent only from the micropylar region; two cells thick at the micropylar margin. Inner integument continuous, the micropyle constricted; thickened around the micropyle. Synergids not haustorial; without large, globular starch grains.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells markedly different in shape costally and intercostally (the costals long-rectangular, the intercostals much longer and fusiform); of similar wall thickness costally and intercostally. Intercostal zones with typical long-cells (though these very long). Mid-intercostal long-cells fusiform; having straight or only gently undulating walls. Microhairs present; elongated; clearly two-celled; panicoid-type. Microhair apical cell wall thinner than that of the basal cell and often collapsed. Microhair basal cells 12–15 microns long. Stomata common. Subsidiaries parallel-sided. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells absent or very rare. Intercostal silica bodies absent. Costal short-cells conspicuously in long rows. Costal silica bodies present in alternate cell files of the costal zones; panicoid-type; nodular.
Transverse section of leaf blade, physiology. Lamina mid-zone in transverse section open.
C3; XyMS+. Mesophyll with radiate chlorenchyma; without fusoids (but with intercostal lacunae). Leaf blade with distinct, prominent adaxial ribs; with the ribs more or less constant in size. Midrib not readily distinguishable; with one bundle only. Bulliforms present in discrete, regular adaxial groups (in some species, between the vascular bundles), or not present in discrete, regular adaxial groups (the groups inconpicuous, or restricted to midrib hinges); in simple fans. Many of the smallest vascular bundles unaccompanied by sclerenchyma. Combined sclerenchyma girders absent. Sclerenchyma all associated with vascular bundles, or not all bundle-associated. The extra sclerenchyma when present, in abaxial groups; abaxial-hypodermal, the groups isolated (opposite the furrows). The lamina margins without fibres.
Culm anatomy. Culm internode bundles in one or two rings.
Cytology. Chromosome base number, x = 12, or 13 (?). 2n = 24, or 26 (?). 2 ploid.
Classification. Watson & Dallwitz (1994): Arundinoideae; Danthonieae (?). Soreng et al. (2015): Arundinoideae; Molinieae. 2–4 species.
Distribution, phytogeography, ecology. Tropical Africa, tropical Asia, Australia.
Commonly adventive. Helophytic.
Economic aspects. Significant weed species: E. articulatus (in North America).
Rusts and smuts. Smuts from Tilletiaceae. Tilletiaceae Tilletia.
References, etc. Leaf anatomical: Metcalfe 1960; studied by us - E. spicatus (Willd.) A. Camus.
Illustrations. • E. spicatus, as E. articulatus: Kunth (1835). • E. spicatus, general aspect, spikelet. • E. globularis: Gibbs Russell et al., 1990. • E. spicatis, inflorescence details: this project. Elytrophorus spicatus. Glomerules of spikelet clusters, on a false spike. • Spikelet of E. spicatus. • E. spicatis, abaxial epidermis of leaf blade: this project. • E. spicatis, abaxial epidermis of leaf blade: this project. • E. spicatis, abaxial epidermis of leaf blade, detailing silica-bodies: this project. • E. spicatus, TS 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: 11th December 2017. delta-intkey.com/grass’.