Schismus P. Beauv.
From the Greek schisma (cleft), referring to the lemma tip.
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. 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; without cross venation; persistent; a fringe of hairs.
Reproductive organization. Plants bisexual, 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, or absent (or the hairs few and short).
Glumes two; more or less equal; shorter than the spikelets to about equalling the spikelets; 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 4–10. 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; from a sinus; non-geniculate; much shorter than the body of the lemma to about as long as the body of the lemma; entered by one vein. Lemmas hairy (pilose dorsally or on the margins). The hairs not in transverse rows. Lemmas non-carinate; 7–9 nerved. Palea present; relatively long; not indurated (membranous); 2-nerved; 2-keeled. Lodicules present; 2; joined, or free; fleshy; ciliate, or glabrous. Stamens 3. Anthers 0.2–0.5 mm long; not penicillate. Ovary glabrous. Styles free to their bases. Stigmas 2.
Fruit, embryo and seedling. Fruit free from both lemma and palea; yellow, shiny; obovate; not grooved; compressed dorsiventrally. 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. 2 ploid. Chromosomes ‘small’.
Taxonomy. Arundinoideae; Danthonieae.
Distribution, ecology, phytogeography. 5 species; Africa, Mediterranean to northwest India. Commonly adventive. Xerophytic; species of open habitats.
Holarctic, Paleotropical, and Cape. Boreal, Tethyan, and Madrean. African and Indomalesian. Euro-Siberian. Macaronesian, Mediterranean, and Irano-Turanian. Saharo-Sindian, Sudano-Angolan, and Namib-Karoo. Indian. European and Siberian. Somalo-Ethiopian.
Rusts and smuts. Rusts — Puccinia. Taxonomically wide-ranging species: Puccinia hordei. Smuts from Ustilaginaceae. Ustilaginaceae — Ustilago.
Economic importance. Important native pasture species: S. arabicus, S. barbatus.
References, etc. Leaf anatomical: Metcalfe 1960 and this project.
Illustrations. • General aspect
Cite this publication as: Watson, L., and Dallwitz, M. J. (1992 onwards). ‘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.’ http://biodiversity.uno.edu/delta/. Version: 18th August 1999. Dallwitz (1980), Dallwitz, Paine and Zurcher (1993 onwards, 1998), and Watson and Dallwitz (1994), and Watson, Dallwitz, and Johnston (1986) should also be cited (see References).
