The grass genera of the world
Habit, vegetative morphology. Wiry perennial; caespitose. Culms 40–80 cm high; herbaceous; conspicuously branched above. Culm nodes glabrous. Culm internodes solid. Plants unarmed. Young shoots intravaginal. Leaves not basally aggregated; non-auriculate; without auricular setae (but hairy in the auricle positions). Leaf blades narrow; 0.2–1.5 mm wide; setaceous (or filiform); without abaxial multicellular glands; without cross venation. Ligule a fringed membrane; very short. Contra-ligule absent.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets.
Inflorescence. Inflorescence of spicate main branches (the branches 12 cm or more long), or a single raceme (the spikelets appressed to the hollows in the rachis, more or less contiguous); when branched, digitate. Primary inflorescence branches 1–2(–3). Inflorescence with axes ending in spikelets (but these imperfect in material seen). Rachides hollowed. Spikelets all partially embedded in the rachis. Inflorescence espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes slender; persistent. Spikelets solitary; secund (on one side of rachis); biseriate; shortly pedicellate, or subsessile.
Female-fertile spikelets. Spikelets 3 mm long; adaxial; compressed dorsiventrally; disarticulating above the glumes; with a distinctly elongated rachilla internode above the glumes and with distinctly elongated rachilla internodes between the florets (the first floret stipitate, the second on an elongate, slender rachilla joint). Rachilla prolonged beyond the uppermost female-fertile floret; hairless (glabrous); the rachilla extension with incomplete florets. Hairy callus present. Callus rather long (hairy at the base).
Glumes present; two; very unequal; shorter than the adjacent lemmas; dorsiventral to the rachis; hairless; glabrous; pointed; awnless; non-carinate (rounded on back); similar in shape and texture, thinly membranous to linear acuminate/setiform. Lower glume much shorter than half length of lowest lemma (about one-sixth); 0 nerved, or 1 nerved. Upper glume 1 nerved. Spikelets with incomplete florets. The incomplete florets distal to the female-fertile florets (terminating the rachilla). The distal incomplete florets 1; merely underdeveloped (reduced to a minute lemma); awnless. Spikelets without proximal incomplete florets.
Female-fertile florets 1. Lemmas similar in texture to the glumes to decidedly firmer than the glumes (membranous); smooth; not becoming indurated; incised; 2 lobed; not deeply cleft (bidentate); delicately awned. Awns 1; median; from a sinus; non-geniculate; flexuous (the tip thin and tortuous); hairless (scabrid); much longer than the body of the lemma (more than twice as long); entered by one vein; persistent. Lemmas hairless; glabrous; non-carinate (rounded on the back); without a germination flap; 3 nerved. Palea present; relatively long; apically notched (slightly 2-dentate); awnless, without apical setae (glabrous); thinner than the lemma (hyaline); not indurated; 2-nerved; 2-keeled (accommodating the rachilla). Lodicules present; 2; free; fleshy (clearly so, and long); glabrous; not toothed; not or scarcely vascularized. Anthers not penicillate; without an apically prolonged connective. Ovary apically glabrous. Styles free to their bases. Stigmas 2; red pigmented.
Fruit, embryo and seedling. Hilum short. Pericarp free (?).
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 (thick, pitted). Microhairs present; more or less spherical to elongated; clearly two-celled; chloridoid-type (basal cell short). Microhair apical cell wall of similar thickness/rigidity to that of the basal cell. Microhair basal cells 6 microns long. Microhair total length/width at septum 2. Microhair apical cell/total length ratio 0.5. Stomata common. Subsidiaries dome-shaped and triangular. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells common; in cork/silica-cell pairs; silicified. Intercostal silica bodies absent, or imperfectly developed; narrowly saddle shaped, or crescentic. Costal short-cells predominantly paired. Costal silica bodies present throughout the costal zones; crescentic (common), or tall-and-narrow, or saddle shaped (numerous, but in reduced form - almost tall-and-narrow, intergrading with crescents); not sharp-pointed.
Transverse section of leaf blade, physiology. Leaf blades largely consisting of midrib. 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. Leaf blade with distinct, prominent adaxial ribs (the section crescentic, with a large broad flat-topped midrib and only 1–2 small ribs on each side). Midrib conspicuous (the blade reduced to relatively small flanges on either side); having a conventional arc of bundles (a large median, and three small ones on either side); with colourless mesophyll adaxially. Bulliforms in conspicuous midrib hinges; in deeply penetrating midrib hinge fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present (with the lamina bundles); forming figures (in the lamina bundles). Sclerenchyma all associated with vascular bundles. The extra sclerenchyma in an adaxial layer. 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. West Indies.
References, etc. Leaf anatomical: this project.
Special comments. Fruit data wanting. Illustrations. • S. fasciculata: Hitchcock (1936). • S. pleiostachya, T.S. of reduced 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’.