The grass genera of the world
Type species: Type: E. olivacea Stapf.
Habit, vegetative morphology. Perennial; rhizomatous, or caespitose. Culms 20–120 cm high; woody and persistent (wiry, bushy), or herbaceous; scandent (sometimes straggling/climbing), or not scandent; branched above, or unbranched above; tuberous, or not tuberous. Culm nodes hairy, or glabrous. Culm leaf sheaths rounded. Culm internodes hollow. Leaves not basally aggregated; non-auriculate. Leaf blades broad, or narrow; cordate, or not cordate, not sagittate; pseudopetiolate, or not pseudopetiolate; without cross venation; disarticulating from the sheaths (in Australia), or persistent (in southern Africa - evidence of shaky generic circumscription); rolled in bud. Ligule a fringe of hairs.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. The spikelets all alike in sexuality.
Inflorescence. Inflorescence of spicate main branches, or paniculate (but usually with sessile spiciform racemes, appressed to the common axis); open, or contracted. Primary inflorescence branches inserted all around the main axis. Rachides hollowed to flattened. Inflorescence espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes persistent. Spikelets solitary, or paired; secund. Pedicel apices discoid. Spikelets consistently in long-and-short combinations (rarely), or not in distinct long-and-short combinations.
Female-fertile spikelets. Spikelets 2.5–6 mm long; elliptic, or lanceolate, or oblanceolate; adaxial; usually compressed dorsiventrally; falling with the glumes. Rachilla terminated by a female-fertile floret. Hairy callus absent.
Glumes present; two; very unequal; (the upper, longer) long relative to the adjacent lemmas; dorsiventral to the rachis; awnless; non-carinate; very dissimilar (the lower tiny, hyaline, the upper membranous and equalling the spikelet). Lower glume 0–3 nerved. Upper glume 3–7 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; 5 nerved; more or less equalling the female-fertile lemmas to decidedly exceeding the female-fertile lemmas; less firm than the female-fertile lemmas to similar in texture to the female-fertile lemmas (but shorter than the G2, which it resembles much more than does the L2); not becoming indurated.
Female-fertile florets 1. Lemmas similar in texture to the glumes to decidedly firmer than the glumes (membranous to leathery); smooth to striate; not becoming indurated; white in fruit, or yellow in fruit; entire; blunt; awnless; densely silky- hairy (all over); non-carinate; having the margins inrolled against the palea; with a clear germination flap; 3–5 nerved. Palea present; relatively long; entire; awnless, without apical setae; 2-nerved; 2-keeled (the margins inrolled). Palea back hairy (between the keels). Lodicules present; 2; fleshy; glabrous. Stamens 3. Anthers not penicillate. Ovary apically glabrous. Styles free to their bases. Stigmas 2; red pigmented.
Fruit, embryo and seedling. Fruit small; compressed dorsiventrally. Hilum short. Embryo large. Endosperm containing only simple 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 broad; curved; 6–12 veined.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells markedly different in shape costally and intercostally; of similar wall thickness costally and intercostally. Intercostal zones sometimes exhibiting many atypical long-cells. Mid-intercostal long-cells rectangular to fusiform (and sometimes very short); having markedly sinuous walls. Microhairs present; panicoid-type; 45–75(–78) microns long; 6–9 microns wide at the septum. Microhair total length/width at septum 5.4–10. Microhair apical cells (19.5–)21–30(–33) microns long. Microhair apical cell/total length ratio 0.33–0.65. Stomata common; 33–51 microns long. Subsidiaries triangular. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells absent or very rare; not paired (usually solitary); not silicified. Costal short-cells conspicuously in long rows. Costal silica bodies panicoid-type; dumb-bell shaped.
Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with radiate chlorenchyma; without adaxial palisade; Isachne-type. Leaf blade adaxially flat. Midrib not readily distinguishable; with one bundle only. Bulliforms present in discrete, regular adaxial groups; in simple fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present. Sclerenchyma all associated with vascular bundles.
Cytology. Chromosome base number, x = 9. 2n = 18. 2 ploid.
Classification. Watson & Dallwitz (1994): Panicoideae; Panicodae; Paniceae. Soreng et al. (2015): Panicoideae; Panicodae; Paniceae; Boivinellinae. 5 species.
Distribution, phytogeography, ecology. Tropical Africa, eastern Australia.
Helophytic, mesophytic, and xerophytic; shade species and species of open habitats; glycophytic. Marshy places, damp grassland and dry forest.
Rusts and smuts. Rusts Puccinia. Taxonomically wide-ranging species: Puccinia levis.
References, etc. Leaf anatomical: this project.
Illustrations. • E. imbricata: Gibbs Russell et al., 1990. • Ligule of E. imbricata. • E. imbricata , inflorescence detail with opened spikelet: this project. Entolasia imbricata. The opened spikelet shows the upper glume (below, left), lower lemma (resembling it, against the axis), the shorter, pale lemma (below) and the palea. • E. stricta, abaxial epidermis of leaf blade: this project. • Leaf blade T.S. of E. stricta, fluorescence image: 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’.