The grass genera of the world
Type species: Type: S. gibba (S.Elliott) Nash.
Including Rhampholepis Stapf
Habit, vegetative morphology. Annual, or perennial; rhizomatous, or stoloniferous, or caespitose, or decumbent. Culms 10–200 cm high; herbaceous; branched above, or unbranched above. The branching simple. Culm nodes glabrous. Culm leaf sheaths rounded. Culm internodes hollow. Leaves not basally aggregated; auriculate, or non-auriculate. Leaf blades linear to linear-lanceolate; narrow; flat, or rolled (convolute); not pseudopetiolate; cross veined, or without cross venation; persistent; rolled in bud. Ligule an unfringed membrane to a fringed membrane.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. The spikelets of sexually distinct forms on the same plant (e.g. S. cingularis), or all alike in sexuality; when of different kinds, hermaphrodite and sterile (the sterile spikelets, when present, at the base of the inflorescence).
Inflorescence. Inflorescence paniculate (with filiform branches); narrowly contracted (usually), or open (rarely); usually spicate. Primary inflorescence branches inserted all around the main axis. Inflorescence espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes persistent. Spikelets not secund; shortly pedicellate. Pedicel apices discoid.
Female-fertile spikelets. Spikelets 0.8–5.2 mm long; elliptic, or lanceolate, or ovate; compressed laterally to not noticeably compressed (gibbous, often oblique); falling with the glumes. Rachilla terminated by a female-fertile floret. Hairy callus absent.
Glumes two; very unequal; (the upper) about equalling the spikelets (the lower 1/5 to 3/4 as long); (the longer) long relative to the adjacent lemmas; awnless; very dissimilar (both membranous or hyaline, prominently ribbed, the upper generally more or less inflated and gibbous). Lower glume 3–7 nerved. Upper glume distinctly saccate; 5–13 nerved. Spikelets with incomplete florets. The incomplete florets proximal to the female-fertile florets. Spikelets with proximal incomplete florets. The proximal incomplete florets 1; paleate, or epaleate. Palea of the proximal incomplete florets when present, fully developed to reduced. The proximal incomplete florets male (rarely), or sterile. The proximal lemmas less gibbous than the upper glume, otherwise more or less resembling it, or occasionally with a transverse row of hairs, and S. fenestrata with two basal windows; awnless; 7 nerved; decidedly exceeding the female-fertile lemmas (about equalling G2); less firm than the female-fertile lemmas; not becoming indurated.
Female-fertile florets 1 (laterally compressed). Lemmas acute, strongly convex; decidedly firmer than the glumes (papery to subcrustaceous); smooth; becoming indurated to not becoming indurated; white in fruit; entire; pointed; awnless; hairless (glossy); non-carinate; having the margins lying flat on the palea (but the margins not hyaline), or having the margins inrolled against the palea; with a clear germination flap; 3 nerved, or 5 nerved (obscurely so). Palea present; relatively long; entire; awnless, without apical setae; textured like the lemma; indurated, or not indurated; 2-nerved. Lodicules present; 2; free; fleshy; glabrous. Stamens 3. Anthers not penicillate. Ovary apically glabrous. Styles free to their bases. Stigmas 2.
Fruit, embryo and seedling. Fruit small; compressed dorsiventrally. Hilum short. Embryo large; waisted. Endosperm hard; without lipid. Embryo without an epiblast; with a scutellar tail; with an elongated mesocotyl internode. Embryonic leaf margins overlapping.
Seedling with a long mesocotyl. First seedling leaf with a well-developed lamina. The lamina broad; supine.
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 with typical long-cells to exhibiting many atypical long-cells. Mid-intercostal long-cells rectangular; having markedly sinuous walls, or having straight or only gently undulating walls. Microhairs present; panicoid-type (but the apical cell sometimes quite broad). Stomata common. Subsidiaries low dome-shaped, or triangular. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells common, or absent or very rare; not paired, or in cork/silica-cell pairs and not paired; silicified, or not silicified. Costal short-cells conspicuously in long rows, or conspicuously in long rows and predominantly paired. Costal silica bodies tall-and-narrow, or panicoid-type (mostly), or acutely-angled (sometimes); mostly nodular, or dumb-bell shaped; sharp-pointed, or not sharp-pointed (rarely).
Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with radiate chlorenchyma (e.g. S. myosuroides), or with non-radiate chlorenchyma (e.g. S. indica); Isachne-type (e.g. S. indica, S. africana), or not Isachne-type (e.g. S. chevalieri); without fusoids (but lacunae sometimes present between the veins near the midrib). Leaf blade with distinct, prominent adaxial ribs. Midrib conspicuous; with one bundle only. Bulliforms often present in discrete, regular adaxial groups, or not present in discrete, regular adaxial groups (confined to the adaxial groove of the midrib in S. chevalieri); when grouped, in simple fans. Many of the smallest vascular bundles unaccompanied by sclerenchyma. Combined sclerenchyma girders absent.
Phytochemistry. Leaves without flavonoid sulphates (2 species).
Cytology. Chromosome base number, x = 9. 2n = 16, 18, 36, and 45. 2, 4, and 5 ploid.
Classification. Watson & Dallwitz (1994): Panicoideae; Panicodae; Paniceae. Soreng et al. (2015): Panicoideae; Panicodae; Paniceae. 30 species.
Distribution, phytogeography, ecology. Tropical and subtropical.
Hydrophytic to helophytic; species of open habitats; glycophytic. In or near water or in wet places.
Economic aspects. Important native pasture species: S. africana, S. myosuroides.
Rusts and smuts. Rusts Puccinia. Taxonomically wide-ranging species: Puccinia emaculata. Smuts from Ustilaginaceae. Ustilaginaceae Sphacelotheca and Ustilago.
References, etc. Leaf anatomical: Metcalfe 1960; this project.
Illustrations. • S. curvata, as Panicum coryophorum: Kunth (1835). • S. curvata: Hook. Ic. Pl. 31 (1922). • S. myosuroides: Gardner, 1952. • General aspect (S. typhura): Gibbs Russell et al., 1990. • S. indica, part of inflorescence in close-up: this project. • S. indica spikelet and pedicels: this project. • S. indica, abaxial epidermis of 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’.