The grass genera of the world
Including Diplax Bennett, Trochera L. Rich.
Excluding Microlaena, Petriella, Tetrarrhena
Habit, vegetative morphology. Annual, or perennial; rhizomatous, or stoloniferous, or caespitose, or decumbent. Culms 6–150 cm high; woody and persistent, or herbaceous; 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. Young shoots intravaginal. Leaves mostly basal, or not basally aggregated; auriculate, or non-auriculate. Leaf blades linear to linear-lanceolate; broad, or narrow; 0.5–12 mm wide; setaceous, or not setaceous; flat, or folded, or rolled; not pseudopetiolate; without cross venation; disarticulating from the sheaths, or persistent. Ligule an unfringed membrane, or a fringed membrane, or a fringe of hairs; truncate; 0.5–3 mm long. Contra-ligule absent.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets; outbreeding.
Inflorescence. Inflorescence few spikeleted to many spikeleted; a single raceme, or paniculate (then narrow, with slender branches); open, or contracted; with capillary branchlets, or without capillary branchlets; espatheate (though in two species the mature inflorescence base is enclosed in the uppermost leaf sheath); not comprising partial inflorescences and foliar organs. Spikelet-bearing axes persistent. Spikelets solitary; secund, or not secund; pedicellate; imbricate, or not imbricate; not in distinct long-and-short combinations.
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. 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 absent. Callus absent.
Glumes two; relatively large; very unequal, or more or less equal; shorter than the spikelets to 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 obtuse); awnless; carinate, or non-carinate; similar (membranous). Lower glume 0.5–1 times the length of the upper glume; 5 nerved. Upper glume 5 nerved. 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; exceeded by 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; becoming indurated, or becoming indurated and not becoming indurated (the first sterile lemma being sometimes non-indurated).
Female-fertile florets 1. Lemmas decidedly firmer than the glumes; usually smooth (and often polished), or striate; becoming indurated; entire; pointed, or blunt (truncate); awnless (usually), or mucronate (occasionally); rarely sparsely hairy, or hairless; usually glabrous, or scabrous; carinate; without a germination flap; 5–7 nerved; with the nerves non-confluent. Palea present; relatively long (narrow); entire; awnless, without apical setae; thinner than the lemma; not indurated; 1-nerved, or 2-nerved, or several nerved, or nerveless (rarely); 2-keeled, or one-keeled (by apposition of the two). Palea keels wingless. Lodicules present; 2; free; membranous; ciliate, or glabrous; toothed (two toothed or irregularly serrate); rather heavily vascularized (Tateoka 1967). Stamens 3, or 4, or 6. Anthers not penicillate; without an apically prolonged connective. Ovary apically glabrous. Styles fused to free to their bases. Stigmas 2; white, or brown.
Fruit, embryo and seedling. Fruit free from both lemma and palea; small; compressed laterally. Hilum long-linear. Embryo small; waisted. Endosperm hard; without lipid; containing compound starch grains. Embryo without an epiblast; with a scutellar tail; with a negligible mesocotyl internode. Embryonic leaf margins overlapping.
Seedling with a short mesocotyl, or with a long mesocotyl. First seedling leaf with a well-developed lamina. The lamina broad, or narrow; erect; 6–12 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 (but the intercostals much larger); 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; 32–44 microns long (e.g. E. pusilla), or 39–60 microns long; 4.9–7.3 microns wide at the septum (in E. rehmannii, E. pusilla), or (7–)8–10(–12) microns wide at the septum. Microhair total length/width at septum 2.7–10. Microhair apical cells 17–49 microns long. Microhair apical cell/total length ratio 0.42–0.71. Stomata common; 24–44(–49) microns long. Subsidiaries low to high dome-shaped. Guard-cells overlapped by the interstomatals. Intercostal short-cells common, or absent or very rare; when seen not paired; when seen silicified, or not silicified. Intercostal silica bodies when present, rounded, or crescentic. Costal short-cells conspicuously in long rows, or predominantly paired, or neither distinctly grouped into long rows nor predominantly paired. Costal silica bodies rounded, or saddle shaped (to almost cubical), or crescentic, or panicoid-type; when panicoid type, cross shaped, or butterfly shaped, or dumb-bell shaped.
Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with non-radiate chlorenchyma; without adaxial palisade; traversed by columns of colourless mesophyll cells, or not traversed by colourless columns (rarely); with arm cells (sometimes, in southern African species), or without arm cells; without fusoids. Leaf blade with distinct, prominent adaxial ribs, or adaxially flat; with the ribs more or less constant in size, or with the ribs very irregular in sizes. Midrib conspicuous, or not readily distinguishable; with one bundle only; with colourless mesophyll adaxially (rarely), or without colourless mesophyll adaxially. 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.
Phytochemistry. Tissues of the culm bases with abundant starch, or with little or no starch. Leaves without flavonoid sulphates (1 species).
Cytology. Chromosome base number, x = 12. 2n = 24 and 48. 2 and 4 ploid.
Classification. Watson & Dallwitz (1994): Bambusoideae; Oryzodae; Ehrharteae. Soreng et al. (2015): Oryzoideae; Ehharteae. 27 species.
Distribution, phytogeography, ecology. Southern and tropical Africa, Mascarene Is., New Zealand.
Commonly adventive. Helophytic (most of the annuals), or mesophytic; shade species (E. erecta), or species of open habitats; halophytic (E. villosa), 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. Smuts from Tilletiaceae and from Ustilaginaceae. 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.
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 stipoides: Hooker, Fl. Tasmaniae (1860). • 6 species, general aspect and spikelet details: Gardner, 1952. • E. capensis: Gibbs Russell et al., 1990. • Proximal lemma detals of E. erecta: this project. Ehrharta erecta. Glumes removed, showing two indurated, transversely ridged, basally appendaged sterile lemmas.
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’.