The grass genera of the world
Type species: Type: E. capensis Thunb.
Including Diplax Bennett, Trochera L. Rich., Microlaena, Petriella, Tetrarrhena, Zotovia
Habit, vegetative morphology. Annual, or perennial; rhizomatous, or stoloniferous, or caespitose, or decumbent. Culms 1–71.16–200 cm high; woody and persistent, or herbaceous; scandent, or not scandent (wiry, often long and scrambling); branched above, or unbranched above. The branching suffrutescent, or simple. Culms tuberous, or not tuberous. Culm nodes hairy, or glabrous. Culm internodes solid, or hollow. Plants unarmed. Young shoots extravaginal, or intravaginal. Leaves mostly basal, or not basally aggregated; auriculate, or non-auriculate. Leaf blades linear, or linear-lanceolate, or lanceolate, or ovate-lanceolate; broad, or narrow; 0.5–12 mm wide; setaceous, or not setaceous; flat (or concave), or folded, or rolled; not pseudopetiolate; cross veined, or without cross venation; disarticulating from the sheaths, or persistent; rolled in bud. Ligule an unfringed membrane, or a fringed membrane, or a fringe of hairs; truncate, or not truncate; 0.5–3 mm long. Contra-ligule absent.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. The spikelets all alike in sexuality (but sometimes cleistogamous, leading to reduced paleas and lodicules, and indehiscent stamens); hermaphrodite. Plants outbreeding, or inbreeding; exposed-cleistogamous, or chasmogamous; with hidden cleistogenes, or without hidden cleistogenes. The hidden cleistogenes when present, in the leaf sheaths.
Inflorescence. Inflorescence few spikeleted, or many spikeleted; a single raceme (spike-like, the axis flexuous), or paniculate (then narrow, with slender branches); open, or contracted; with capillary branchlets, or without capillary branchlets; non-digitate; espatheate (though in two species (Ehrhatra sens str.) the mature inflorescence base is enclosed in the uppermost leaf sheath); not comprising partial inflorescences and foliar organs. Spikelets solitary; secund, or not secund; subsessile, or pedicellate; imbricate, or not imbricate.
Female-fertile spikelets. Spikelets 2–17 mm long; compressed laterally, or not noticeably compressed; disarticulating above the glumes; not disarticulating between the florets; with conventional internode spacings, or with a distinctly elongated rachilla internode above the glumes (i.e., beneath the empty lemmas). Rachilla inconspicuously prolonged beyond the uppermost female-fertile floret, or terminated by a female-fertile floret; hairy, or hairless; the rachilla extension when present, naked. Hairy callus present, or absent. Callus absent.
Glumes two; minute, or relatively large; very unequal (the G2 longer), or more or less equal; shorter than the spikelets, or about equalling the spikelets, or exceeding the spikelets; shorter than the adjacent lemmas, or long relative to the adjacent lemmas; hairless; glabrous, or scabrous; pointed, or not pointed (blunt to truncate); awnless; carinate, or non-carinate; very dissimilar, or similar (membranous to leathery). Lower glume 0.5–1 times the length of the upper glume; shorter than the lowest lemma; much shorter than half length of lowest lemma; 0–3 nerved, or 5 nerved. Upper glume 0–1 nerved, or 3–5 nerved; not prickly. Spikelets with incomplete florets. The incomplete florets proximal to the female-fertile florets. Spikelets with proximal incomplete florets. The proximal incomplete florets 2; epaleate; sterile. The proximal lemmas curiously varied in form, often hardened and transversely ridged, the lower sometimes bearing a knob-like appendage (elaieosome?) at its base; awned (abruptly from the back, or the lemma tapering into the awn), or awnless; 0–9 nerved; exceeded by the female-fertile lemmas, or more or less equalling the female-fertile lemmas, or decidedly exceeding the female-fertile lemmas; less firm than the female-fertile lemmas, or similar in texture to the female-fertile lemmas, or decidedly firmer than the female-fertile lemmas; becoming indurated, or not becoming indurated.
Female-fertile florets 1. Lemmas similar in texture to the glumes, or decidedly firmer than the glumes; usually smooth (and often polished), or striate; becoming indurated, or not becoming indurated; entire; pointed, or blunt (truncate); awnless (usually), or mucronate (occasionally), or awned (tapered into the stout awn). Awns not of the triple/trifid, basal column type (1/1); (when present) 1; median; apical; non-geniculate; hairless; much shorter than the body of the lemma. Lemmas rarely sparsely hairy, or hairless; usually glabrous, or scabrous; carinate, or non-carinate; without a germination flap; 1–7 nerved; with the nerves non-confluent. Palea present; relatively long (narrow), or conspicuous but relatively short, or very reduced; entire; awnless, without apical setae; thinner than the lemma; not indurated; nerveless (rarely), or 1-nerved, or 2-nerved, or several nerved; keel-less, or one-keeled (by apposition of the two), or 2-keeled. Palea keels wingless. Lodicules present; 2; free; membranous; ciliate, or glabrous; toothed (two toothed or irregularly serrate), or not toothed; rather heavily vascularized (Tateoka 1967). Stamens 2–6. Anthers 1–3 mm long; not penicillate; without an apically prolonged connective. Ovary apically glabrous; without a conspicuous apical appendage. Styles fused to free to their bases. Stigmas 2; white, or brown.
Fruit, embryo and seedling. Fruit free from both lemma and palea; small, or medium sized; oblong-linear or ellipsoid; compressed laterally. Hilum short, or long-linear. Embryo small; waisted, or not waisted. Endosperm hard; without lipid; containing compound starch grains. Embryo with an epiblast, or without an epiblast; with a scutellar tail; with an elongated mesocotyl internode, or with a negligible mesocotyl internode. Embryonic leaf margins overlapping.
Seedling with a short mesocotyl, or with a long mesocotyl; with a tight coleoptile. First seedling leaf with a well-developed lamina. The lamina broad, or narrow; erect, or curved; 5–12 veined.
Ovule, embryology. 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 similar in shape costally and intercostally; of similar wall thickness costally and intercostally. Mid-intercostal long-cells rectangular, or fusiform; having markedly sinuous walls, or having straight or only gently undulating walls. Microhairs present, or absent; panicoid-type; 30–63 microns long; 4.5–18 microns wide at the septum. Microhair total length/width at septum 2.1–10. Microhair apical cells 10.5–27.41–49 microns long. Microhair apical cell/total length ratio 0.31–0.565–0.71. Stomata common (2/3), or absent or very rare (1/3); 21–30.91–49 microns long. Subsidiaries dome-shaped (3/3), or triangular (2/3). Guard-cells overlapped by the interstomatals (1/3), or overlapping to flush with the interstomatals (2/3). Intercostal short-cells common (3/3), or absent or very rare (2/3); in cork/silica-cell pairs (1/2), or not paired (1/2); silicified (2/3), or not silicified (2/3). Intercostal silica bodies rounded (2/2), or crescentic (2/2), or tall-and-narrow (1/2). Costal short-cells conspicuously in long rows (3/3), or predominantly paired (1/3), or neither distinctly grouped into long rows nor predominantly paired (1/3). Costal silica bodies rounded (2/3), or saddle shaped (1/3), or crescentic (1/3), or panicoid-type (3/3); cross shaped (2/2), or butterfly shaped (2/2), or dumb-bell shaped (2/2).
Transverse section of leaf blade, physiology. C3 (3/3); XyMS+ (3/3). PBS cells without a suberised lamella (1/1). Mesophyll with radiate chlorenchyma (1/3), or with non-radiate chlorenchyma (3/3); without adaxial palisade (3/3); traversed by columns of colourless mesophyll cells (1/3), or not traversed by colourless columns (3/3); with arm cells (1/3), or without arm cells (3/3); without fusoids (3/3). Leaf blade with distinct, prominent adaxial ribs (2/3), or nodular in section (2/3), or adaxially flat (2/3); with the ribs more or less constant in size (3/3), or with the ribs very irregular in sizes (1/3). Midrib conspicuous (2/3), or not readily distinguishable (2/3); with one bundle only (3/3); with colourless mesophyll adaxially (1/3), or without colourless mesophyll adaxially (3/3). Bulliforms present in discrete, regular adaxial groups (3/3); in simple fans (3/3). All the vascular bundles accompanied by sclerenchyma (3/3). Combined sclerenchyma girders present (3/3); forming figures (2/2), or nowhere forming figures (1/2). Sclerenchyma all associated with vascular bundles (3/3).
Culm anatomy. Culm internode bundles in one or two rings (1/1).
Phytochemistry. Tissues of the culm bases with abundant starch (2/2), or with little or no starch (1/2). Leaves containing flavonoid sulphates (1/2), or without flavonoid sulphates (1/2).
Cytology. Chromosome base number, x = 10 (1/2), or 12 (1/2). 2n = 24 and 48. 2 and 4 ploid (1/1).
Classification. Watson & Dallwitz (1994): Bambusoideae; Oryzodae; Ehrharteae. Soreng et al. (2015): Oryzoideae; Ehharteae. 37 species.
Distribution, phytogeography, ecology. Southern and tropical Africa, Mascarene Is., New Zealand, Philippines, Java to Australasia.
Commonly adventive, or not commonly adventive. Helophytic (most of the annuals), or mesophytic; shade species, or species of open habitats; halophytic, or glycophytic. Diverse habitats, with E. villosa in coastal sand dunes.
Economic aspects. Significant weed species: E. brevifolia, E. calycina, E. dura, E. erecta, E. longiflora, E. villosa. Cultivated fodder: E. erecta, E. calycina. Important native pasture species: E. erecta.
Rusts and smuts. Rusts Puccinia, or no rusts recorded. Taxonomically wide-ranging species: no wide-ranging rust species. Smuts from Tilletiaceae and from Ustilaginaceae, or not recorded. Tilletiaceae Tilletia. Ustilaginaceae Ustilago.
References, etc. Morphological/taxonomic: Willemse 1982; Gibbs Russell and Ellis 1987, 1988; Gibbs Russell 1987. Leaf anatomical: Ellis 1987 and this project.
Special comments. This description combines the descriptions of Ehrharta sensu stricto, Microlaena and Tetrarrhena, which are described separately in this data set but merged in some recent treatments. The figures in parentheses either reflect breakdown figures for the segregate genera (when the sensu lato version exhibits more than one character state), and/or that a character is unknown for one or more of the three seggregates. Illustrations. • Ehrharta colensoi: Hooker, Fl. Novae-Zelandiae (1853). • Ehrharta juncea (as Tetrarrhena tenacissima): Hooker, Fl. Tasmaniae (1860). • E. longiflora, as E. urvilleana: Lamson-Scribner (1890). • Ehrharta tasmanica (as Diplax), with Microlaena gunnii = stipoides: Hooker, Fl. Tasmaniae (1860). • 6 species: Gardner, 1952. • E. capensis: Gibbs Russell et al., 1990. • Proximal lemmas of E. erecta: this project. Ehrharta erecta. Glumes removed, showing two indurated, transversely ridged, basally appendaged sterile lemmas. • Ehrharta colensoi: Hooker, Fl. Novae-Zelandiae (1853). • Ehrharta juncea (as Tetrarrhena tenacissima): Hooker, Fl. Tasmaniae (1860). • Microlaena stipoides (as M. gunnii) and Ehrharta tasmanica (as Diplax). • M. stipoides, general structure. • Spikelet base details of M. stipoides: this project. Microlaena stipoides. Minute glumes, long internode between them and the lemma base, hairy callus. • Lodicules and gynoecium (M. stipoides)). • M. stipoides, abaxial epidermis of leaf blade: this project. • M. stipoides, leaf blade TS: this project. • M. stipoides, leaf blade TS: this project. • General aspect, spikelet (Tetrarrhena laevis). • T. laevis, abaxial epidermis of leaf blade: this project. • T. juncea, TS 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’.