The grass genera of the world
Habit, vegetative morphology. Small, delicate perennial; caespitose. Culms unbranched above. Culm nodes glabrous. Culm internodes solid. Leaves mostly basal; non-auriculate. Leaf blades narrow; setaceous (pilose); without cross venation; persistent. Ligule present; an unfringed membrane (jagged, small, with a conspicuous fringe adjoining it on the lamina); 0.25 mm long.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets.
Inflorescence. Inflorescence of spicate main branches; with thin, delicate rachides. Primary inflorescence branches few. Inflorescence espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes persistent. Spikelets solitary; secund; biseriate; pedicellate (the pedicels appearing bipartite - inside glabrous, outside pilose).
Female-fertile spikelets. Spikelets unconventional (lacking an organ, assumed here to be the lower glume); 1 mm long; turbinate; abaxial; compressed dorsiventrally; falling with the glumes (the pedicel splitting lengthways). Rachilla terminated by a female-fertile floret. Hairy callus present (constituted by the length of pedicel which comes away).
Glumes present; one per spikelet; the upper, only glume long relative to the adjacent lemmas; dorsiventral to the rachis; hairy (pilose with white hairs, and a subterminal transverse fringe); awnless; non-carinate. Upper glume faintly 5 nerved. Spikelets with incomplete florets. The incomplete florets proximal to the female-fertile florets. The proximal incomplete florets 1; sterile. The proximal lemmas membranous, pilose with white hairs and a subterminal fringe, like the glume, but apparently with a basal, pilose appendage fused to the outside of the pedicel - cf. Centrochloa); awnless; faintly 3 nerved; more or less equalling the female-fertile lemmas; less firm than the female-fertile lemmas; not becoming indurated.
Female-fertile florets 1. Lemmas decidedly firmer than the glumes; becoming indurated (thinly); brown in fruit (shiny); entire; pointed, or blunt; awnless (but abruptly beaked, the beak hooked); hairless; non-carinate; having the margins lying flat on the palea; with a clear germination flap; faintly 3 nerved. Palea present; relatively long; 2-nerved (thinly indurated); 2-keeled. Lodicules present; 2; free; fleshy; glabrous; not or scarcely vascularized. Stamens 3. Ovary apically glabrous. Styles free to their bases. Stigmas 2.
Fruit, embryo and seedling. Fruit free from both lemma and palea; small (about 1 mm long); compressed dorsiventrally. Hilum short. Embryo large. Endosperm hard.
Abaxial leaf blade epidermis. Costal/intercostal zonation lacking. Papillae absent. Mid-intercostal long-cells having markedly sinuous walls. Microhairs present; panicoid-type; (42–)45–51(–54) microns long; 5.4–5.7–6.9 microns wide at the septum. Microhair total length/width at septum 6.5–9.5. Microhair apical cells (22–)33–35(–38) microns long. Microhair apical cell/total length ratio 0.53–0.7. Stomata absent or very rare. Intercostal short-cells common; in cork/silica-cell pairs. Large macrohairs present, with complex cushion bases. Costal short-cells predominantly paired (all short-cells in cc/sc pairs). Costal silica bodies rounded (a few), or tall-and-narrow, or panicoid-type (basically this type, commonly reduced); often one-sided cross shaped (often with sharp points); sharp-pointed (often has sharp points on the crosses).
Transverse section of leaf blade, physiology. C4; XyMS. Leaf blade with distinct, prominent adaxial ribs; with the ribs very irregular in sizes. Midrib conspicuous (a larger rib); having a conventional arc of bundles (1 large and 2 small bundles). Bulliforms not present in discrete, regular adaxial groups. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders absent. Sclerenchyma not all bundle-associated. The extra sclerenchyma in a continuous abaxial layer.
Classification. Watson & Dallwitz (1994): Panicoideae; Panicodae; Paniceae. Soreng et al. (2015): Panicoideae; Panicodae; Paspaleae; Paspalinae. 1 species (S. kegelii).
Distribution, phytogeography, ecology. Tropical South America.
References, etc. Leaf anatomical: studied by us.
Illustrations. • S. kegelii, as S. setifolia: Hoehne (1839), Estrateigicas de Matto-Grosso ao Amazonas. • S. kegelii, with Centrochloa singularis: Swallen, J. Wash. Acad. Sci. 25 (1935)
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: 11th December 2017. delta-intkey.com/grass’.