The grass genera of the world
Habit, vegetative morphology. Perennial; densely caespitose. Culms 80–200 cm high; herbaceous; unbranched above. Culm nodes glabrous. Culm internodes solid. Plants unarmed. Young shoots intravaginal. Leaves not basally aggregated; non-auriculate. Leaf blades linear; narrow; 2–4 mm wide; rolled; not pseudopetiolate; without cross venation; persistent; rolled in bud. Ligule a fringed membrane, or a fringe of hairs; truncate; 0.3–1 mm long. Contra-ligule present (as a line of hairs, in S. jucunda), or absent.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets.
Inflorescence. Inflorescence paniculate (erect, narrow, often interrupted); open; espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes persistent. Spikelets solitary; not secund; pedicellate.
Female-fertile spikelets. Spikelets 12–30 mm long; not noticeably compressed; disarticulating above the glumes. Rachilla terminated by a female-fertile floret. Hairy callus present (densely but shortly bearded). Callus pointed to blunt (shallowly bilobed).
Glumes two; more or less equal; long relative to the adjacent lemmas; free; hairless; glabrous; pointed (acute to acuminate); awned, or awnless; non-carinate (rounded on the back); similar (narrow, the nerves evanescent). Lower glume about equalling the lowest lemma; usually 3 nerved. Upper glume 3 nerved, or 5 nerved. Spikelets with female-fertile florets only; without proximal incomplete florets.
Female-fertile florets 1. Lemmas subcylindrical, with involute margins, scarcely narrowed above; not convolute (involute); decidedly firmer than the glumes; becoming indurated to not becoming indurated (leathery to cartilaginous); not deeply cleft; awned (cf. Aristida). Awns triple or trifid, commonly with a basal column (or at least with the three spreading awns twisted together basally); apical; non-geniculate; hairless (glabrous or scabrid); about as long as the body of the lemma to much longer than the body of the lemma; persistent. Lemmas hairless (glabrous or scabrid); non-carinate; without a germination flap; 3 nerved; with the nerves non-confluent. Palea present; conspicuous but relatively short (small, scale-like); tightly clasped by the lemma; entire (obtuse); awnless, without apical setae (glabrous); thinner than the lemma; not indurated (leathery below); 2-nerved; 2-keeled (grooved). Palea keels wingless; glabrous. Lodicules present (about equalling or exceeding the palea); 2; free; membranous; glabrous; toothed; heavily vascularized. Stamens 3. Anthers 5–6 mm long; not penicillate; without an apically prolonged connective. Ovary apically glabrous. Styles free to their bases. Stigmas 2 (plumose); white.
Fruit, embryo and seedling. Fruit free from both lemma and palea (but tightly enclosed by the lemma); medium sized (8–10 mm long); fusiform; longitudinally grooved; compressed dorsiventrally. Hilum long-linear. Embryo small (no more than 1/4 grain length). Endosperm containing compound starch grains. Embryo without an epiblast; without a scutellar tail; with an elongated mesocotyl internode. Embryonic leaf margins meeting.
First seedling leaf with a well-developed lamina. The lamina narrow; erect; 5 veined.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs present; panicoid-type. Stomata common. Subsidiaries dome-shaped, or dome-shaped and triangular. Costal short-cells conspicuously in long rows. Costal silica bodies panicoid-type; not sharp-pointed.
Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with non-radiate chlorenchyma. Leaf blade with distinct, prominent adaxial ribs; with the ribs very irregular in sizes. Midrib not readily distinguishable; with one bundle only. Bulliforms present in discrete, regular adaxial groups. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present (with most bundles); forming figures (with most bundles). Sclerenchyma not all bundle-associated. The extra sclerenchyma in abaxial groups; abaxial-hypodermal, the groups isolated (opposite the bulliforms).
Cytology. Chromosome base number, x = 11. 2n = 22.
Classification. Watson & Dallwitz (1994): Arundinoideae; Aristideae. Soreng et al. (2015): Aristidoideae; Aristideae. 4 species.
Distribution, phytogeography, ecology. South Africa.
Illustrations. • General aspect (S. angolensis): 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’.