The grass genera of the world
Type species: Type: S. barbatus (L.) Thell.
Including Electra Panz., Hemisacris Steud.
Habit, vegetative morphology. Annual, or perennial (weakly, infrequently); caespitose (rarely), or decumbent (low). Culms 3–40 cm high; herbaceous; unbranched above; not tuberous. Culm nodes glabrous. Culm internodes solid, or hollow. Leaves non-auriculate. Leaf blades linear to linear-lanceolate; narrow; 0.5–2.5 mm wide; setaceous, or not setaceous; flat, or rolled (convolute); without abaxial multicellular glands; not pseudopetiolate; without cross venation; persistent. Ligule a fringe of hairs.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets.
Inflorescence. Inflorescence paniculate; contracted; loosely spicate; espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes persistent. Spikelets solitary; not secund; pedicellate.
Female-fertile spikelets. Spikelets 4–8 mm long; slightly compressed laterally; falling with the glumes (falling entire), or disarticulating above the glumes; when disarticulating above the glumes, disarticulating between the florets (the upper florets falling singly, then the lower florets, glumes and pedicel falling together); with conventional internode spacings. Rachilla prolonged beyond the uppermost female-fertile floret; the rachilla extension with incomplete florets. Hairy callus present (villous). Callus shorter than the rachilla internodes blunt.
Glumes two; more or less equal; shorter than the spikelets to about equalling the spikelets, or exceeding the spikelets (rarely); long relative to the adjacent lemmas; free (widely separated); awnless; similar (herbaceous-membranous, the margins hyaline). Lower glume 5–7 nerved. Upper glume 3–7 nerved. Spikelets with incomplete florets. The incomplete florets distal to the female-fertile florets. The distal incomplete florets merely underdeveloped. Spikelets without proximal incomplete florets.
Female-fertile florets (3–)4–7. Lemmas similar in texture to the glumes (herbaceous, the lobes and margins hyaline); not becoming indurated; incised (to merely emarginate); 2 lobed; deeply cleft (bifid), or not deeply cleft (emarginate); awnless, or mucronate (from the sinus), or awned. Awns when present, 1; when present, median; from a sinus; non-geniculate; much shorter than the body of the lemma to about as long as the body of the lemma (usually scarcely exceeding the lobes); entered by one vein. Awn bases not twisted. Lemmas hairy (pilose dorsally or on the margins). The hairs scattered or in tufts (marginal), or not in tufts; not in transverse rows (sometimes in longitudinal rows). Lemmas non-carinate; 7–9 nerved. Palea present; relatively long; awnless, without apical setae; membranous, not indurated; 2-nerved; 2-keeled. Palea back glabrous (but sometimes with hair tufts on the margins). Lodicules present; 2; joined, or free; fleshy; ciliate (usually with both bristles and microhairs). Stamens 3. Anthers 0.2–0.5 mm long; not penicillate. Ovary apically glabrous. Styles free to their bases. Stigmas 2.
Fruit, embryo and seedling. Fruit free from both lemma and palea; yellow, shiny; elliptical to obovate; not grooved; compressed dorsiventrally (lorate). Hilum short. Embryo large. Endosperm hard; without lipid; containing compound 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; having markedly sinuous walls. Microhairs present; elongated; clearly two-celled; panicoid-type. Microhair apical cell wall thinner than that of the basal cell and often collapsed. Microhairs 36–39–45 microns long. Microhair basal cells 18–21 microns long. Microhairs (6.9–)7.5–8.4(–9) microns wide at the septum. Microhair total length/width at septum 4–5.6. Microhair apical cells (19.5–)21–22.5(–24) microns long. Microhair apical cell/total length ratio 0.53–0.62. Stomata common; (19–)21–22(–24) microns long. Subsidiaries dome-shaped. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells common; not paired (solitary); not silicified. Intercostal silica bodies imperfectly developed. Costal short-cells conspicuously in long rows. Costal silica bodies present in alternate cell files of the costal zones; panicoid-type, or saddle shaped (or almost so), or horizontally-elongated crenate/sinuous (rarely); often (?) dumb-bell shaped; not sharp-pointed.
Transverse section of leaf blade, physiology. Lamina mid-zone in transverse section open.
C3; XyMS+. Mesophyll with radiate chlorenchyma, or with non-radiate chlorenchyma. Leaf blade with distinct, prominent adaxial ribs, or nodular in section; with the ribs more or less constant in size. Midrib not readily distinguishable; with one bundle only. Bulliforms not present in discrete, regular adaxial groups (bulliforms ill defined and small, save for the midrib hinges). All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present, or absent; forming figures. Sclerenchyma all associated with vascular bundles. The lamina margins with fibres.
Special diagnostic feature. Female-fertile lemmas awnless, mucronate or with a short straight awn.
Cytology. Chromosome base number, x = 6. 2n = 12, 24, 36, 48, and 72. 2 ploid. Chromosomes small.
Classification. Watson & Dallwitz (1994): Arundinoideae; Danthonieae. Soreng et al. (2015): Danthonioideae; Danthonieae. 4 species (with Karroochloa schismoides excluded).
Distribution, phytogeography, ecology. Africa, Mediterranean to northwest India.
Commonly adventive. Xerophytic; species of open habitats.
Economic aspects. Important native pasture species: S. arabicus, S. barbatus.
Rusts and smuts. Rusts Puccinia. Taxonomically wide-ranging species: Puccinia hordei. Smuts from Ustilaginaceae. Ustilaginaceae Ustilago.
References, etc. Leaf anatomical: Metcalfe 1960 and this project.
Illustrations. • S. barbatus (as S. marginatus), with Megastachya mucronata (as M. owariensis), Eleusine coracana and Uniola paniculata (as U. maritima): P. Beauv. (1812). • S. barbatus: Fl. Iraq, 1968. • General aspect (S. barbatus): Gibbs Russell et al., 1990
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’.