The grass genera of the world
Habit, vegetative morphology. Annual, or perennial; caespitose. Culms 70–120 cm high; herbaceous. Leaves not basally aggregated; non-auriculate. Leaf blades linear; narrow; without abaxial multicellular glands; not pseudopetiolate; without cross venation. Ligule a fringed membrane (short).
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets.
Inflorescence. Inflorescence of spicate main branches (usually 2–6 sessile, flexuous spikes); digitate. Primary inflorescence branches (1–)2–6. Inflorescence espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes persistent. Spikelets solitary; secund (on one side of the rachis); biseriate; sessile; imbricate.
Female-fertile spikelets. Spikelets strongly compressed laterally; disarticulating above the glumes. Rachilla prolonged beyond the uppermost female-fertile floret. Hairy callus present.
Glumes two; very unequal; exceeding the spikelets; long relative to the adjacent lemmas (exceeding it); free; hairless; pointed; awned (G1, sometimes), or awnless; carinate; similar (persistent, narrow or setaceous, subhyaline, divergent). Lower glume 1 nerved. Upper glume 1 nerved. Spikelets with female-fertile florets only, or with incomplete florets. The incomplete florets when present, distal to the female-fertile florets. The distal incomplete florets when present, 1; awned. Spikelets without proximal incomplete florets.
Female-fertile florets 1. Lemmas completely covering the palea; decidedly firmer than the glumes (often blackened at maturity); incised; 2 lobed; not deeply cleft (apically bifid); awned. Awns 1; median; from a sinus; non-geniculate, or geniculate; much longer than the body of the lemma (very long, flexuous, tangling one another). Lemmas hairy (with appressed hairs); non-carinate (rounded on the back); 3 nerved. Palea present; 2-nerved; 2-keeled. Lodicules present; 2; free; fleshy; glabrous. Stamens 2–3. Ovary apically glabrous. Styles free to their bases. Stigmas 2.
Fruit, embryo and seedling. Fruit free from both lemma and palea; ellipsoid; compressed laterally. Hilum short. Pericarp free. Embryo large.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae present; intercostal. Intercostal papillae not over-arching the stomata; consisting of one oblique swelling per cell. Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs present; more or less spherical to elongated; clearly two-celled; chloridoid-type. Microhair apical cell wall of similar thickness/rigidity to that of the basal cell. Microhairs 21–24 microns long. Microhair basal cells 15–18 microns long. Microhairs 9–10–10.2 microns wide at the septum. Microhair total length/width at septum 2.2–2.7. Microhair apical cells 7.5–9.6–10.5 microns long. Microhair apical cell/total length ratio 0.36–0.46. Stomata common; 19.5–21 microns long. Subsidiaries triangular. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells absent or very rare; not paired. Intercostal silica bodies absent. Large prickles present costally. Costal short-cells conspicuously in long rows. Costal silica bodies present in alternate cell files of the costal zones; exclusively saddle shaped; not sharp-pointed.
Transverse section of leaf blade, physiology. Lamina mid-zone in transverse section open.
C4; XyMS+. PCR sheaths of the primary vascular bundles interrupted; interrupted both abaxially and adaxially. PCR sheath extensions absent. Mesophyll with radiate chlorenchyma. Leaf blade adaxially flat. Midrib not readily distinguishable; with one bundle only. Bulliforms present in discrete, regular adaxial groups; in simple fans and associated with colourless mesophyll cells to form deeply-penetrating fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present (with all the bundles); forming figures (in all the bundles). Sclerenchyma all associated with vascular bundles. The lamina margins with fibres.
Classification. Watson & Dallwitz (1994): Chloridoideae; main chloridoid assemblage. Soreng et al. (2015): Chloridoideae; Cynodonteae; Eleusininae. 2 species.
Distribution, phytogeography, ecology. Tropical Africa, Asia.
Species of open habitats. Savanna, hardpans and seasonally flooded flats.
References, etc. Leaf anatomical: this project.
Illustrations. • S. gracilis: Kunth (1835). • S. transiens, general aspect: 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’.