The grass genera of the world
Couch Grasses, Star Grasses.
Type species: Type: C. dactylon (L.) Pers.
Including Capriola Adans., Dactilon Vill., Fibichia Koel.
Habit, vegetative morphology. Perennial; rhizomatous and stoloniferous (often sward-forming). Culms 4–60(–100) cm high; herbaceous. Culm nodes glabrous. Culm internodes hollow. Leaves not basally aggregated; non-auriculate. Leaf blades linear; narrow; setaceous, or not setaceous; flat, or folded; without abaxial multicellular glands; not pseudopetiolate; without cross venation; persistent; rolled in bud, or once-folded in bud. Ligule present; a fringed membrane (very short), or a fringe of hairs.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets; outbreeding.
Inflorescence. Inflorescence of spicate main branches; digitate, or subdigitate (sometimes in two or more closely spaced whorls). Primary inflorescence branches 2–20. Inflorescence with axes ending in spikelets. Rachides flattened. Inflorescence espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes persistent. Spikelets solitary; secund; biseriate.
Female-fertile spikelets. Spikelets 1.7–3 mm long; adaxial; compressed laterally; disarticulating above the glumes, or disarticulating between the glumes. Rachilla prolonged beyond the uppermost female-fertile floret, or terminated by a female-fertile floret (C. incompletus); hairless; the rachilla extension (when present) with incomplete florets (minute), or naked. Hairy callus absent.
Glumes two; very unequal to more or less equal; usually shorter than the spikelets, or about equalling the spikelets; shorter than the adjacent lemmas; dorsiventral to the rachis to lateral to the rachis; pointed; awnless; carinate; similar (narrow, lanceolate). Lower glume 1 nerved. Upper glume 1 nerved, or 1–3 nerved. Spikelets with female-fertile florets only (normally), or with incomplete florets. The incomplete florets (when present) distal to the female-fertile florets. The distal incomplete florets (if detectable) 1; merely underdeveloped (usually minute and greatly reduced). Spikelets without proximal incomplete florets.
Female-fertile florets 1. Lemmas similar in texture to the glumes to decidedly firmer than the glumes (firmly cartilaginous); not becoming indurated; entire; pointed, or blunt; awnless; ciliate on the keel and lateral nerves, usually glabrous on the flanks; carinate; 1–4 nerved. Palea present; relatively long; entire to apically notched; awnless, without apical setae; textured like the lemma; not indurated; 2-nerved. Lodicules present; free; fleshy; glabrous. Stamens 3. Anthers 0.6–1.7 mm long; not penicillate. Ovary apically glabrous. Styles free to their bases. Stigmas 2; red pigmented.
Fruit, embryo and seedling. Fruit free from both lemma and palea; small; ellipsoid; compressed laterally, or trigonous. Hilum short. Pericarp fused. Embryo large. Endosperm containing compound starch grains. Embryo with an epiblast; with a scutellar tail; with an elongated mesocotyl internode. Embryonic leaf margins meeting.
Seedling with a long mesocotyl; with a loose coleoptile. First seedling leaf with a well-developed lamina. The lamina broad; curved; 7–9 veined.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae present; costal and intercostal. Intercostal papillae over-arching the stomata, or not over-arching the stomata; consisting of one symmetrical projection per cell to several per cell (usually as finger-like projections). Long-cells similar in shape costally and intercostally; of similar wall thickness costally and intercostally. Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs present; more or less spherical, or elongated; clearly two-celled, or ostensibly one-celled (occasionally); chloridoid-type (sometimes sunken). Microhair apical cell wall of similar thickness/rigidity to that of the basal cell. Microhairs 15–24 microns long. Microhair basal cells 6 microns long. Microhairs 10.5–15 microns wide at the septum. Microhair total length/width at septum 1.4–1.9. Microhair apical cells 9–16 microns long. Microhair apical cell/total length ratio 0.52–0.8. Stomata common; 18–21 microns long. Subsidiaries non-papillate; low dome-shaped and triangular. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells common, or absent or very rare; not paired (usually solitary); silicified, or not silicified. Intercostal silica bodies absent, or imperfectly developed; when present, tall-and-narrow. Costal short-cells conspicuously in long rows. Costal silica bodies present in alternate cell files of the costal zones; saddle shaped, or tall-and-narrow.
Transverse section of leaf blade, physiology. Lamina mid-zone in transverse section open.
C4; biochemical type NADME (2 species); XyMS+. PCR sheath outlines even. PCR sheaths of the primary vascular bundles interrupted; interrupted abaxially only. PCR sheath extensions absent. PCR cells without a suberised lamella. PCR cell chloroplasts elongated; with well developed grana; centripetal. Mesophyll with radiate chlorenchyma; traversed by columns of colourless mesophyll cells. Leaf blade adaxially flat. Midrib conspicuous; with one bundle only, or having a conventional arc of bundles. Bulliforms present in discrete, regular adaxial groups; associated with colourless mesophyll cells to form deeply-penetrating fans (these linked with the traversing colourless columns). All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present; forming figures, or nowhere forming figures. Sclerenchyma all associated with vascular bundles. The lamina margins with fibres.
Culm anatomy. Culm internode bundles in one or two rings.
Phytochemistry. Tissues of the culm bases with abundant starch. Leaves containing flavonoid sulphates (in some material of two species), or without flavonoid sulphates (3 species).
Cytology. Chromosome base number, x = 9 and 10. 2n = 16, 18, 27, 36, 40, and 54. 2, 3, 4, and 6 ploid. Chromosomes small. Nucleoli persistent.
Classification. Watson & Dallwitz (1994): Chloridoideae; main chloridoid assemblage. Soreng et al. (2015): Chloridoideae; Cynodonteae; Eleusininae. 10 species.
Distribution, phytogeography, ecology. Tropical and subtropical.
Commonly adventive. Mesophytic, or xerophytic; species of open habitats; halophytic and glycophytic. Disturbed and arable land, weedy and sandy places, seashores.
Economic aspects. Significant weed species: C. dactylon (sometimes, in arable land), C. aethiopicus, C. incompletus, C. plectostachyus. Important native pasture species: C. dactylon, C. nlemfuensis, C. aethiopicus, C. plectostachyus. Lawns and/or playing fields: C. dactylon (Bermuda, Couch), C. transvaalensis etc.
Hybrids. Intergeneric hybrids with Chloris (×Cynochloris Clifford & Everist: several species involved).
Rusts and smuts. Rusts Puccinia. Taxonomically wide-ranging species: Puccinia graminis. Smuts from Ustilaginaceae. Ustilaginaceae Sorosporium and Ustilago.
References, etc. Leaf anatomical: this project.
Illustrations. • C. dactylon: Fl. W. Trop. Afr. (1936). • C. dactylon: Gibbs Russell et al., 1990. • Vegetative shoot (C. dactylon). • Inflorescence detail (C. dactylon). • Inflorescence detail (C. dactylon). • Inflorescence detail (C. dactylon). • Spikelet (C. dactylon). • Flower (C. dactylon). • C. dactylon, abaxial epidermis of leaf blade: this project. • C. dactylon, abaxial epidermis of leaf blade: this project. • C. dactylon, Leaf blade T.S.: this project. • C. dactylon, Leaf blade T.S.: this project. • Pollen antigens: Watson and Knox (1976). • Pollen antigens: cross-reactions against anti-Lolium serum. • Pollen antigens: cross-reactions against anti-Lolium serum. • Heat stable pollen antigens (allergens): cross-reactions against anti-Lolium serum. • Pollen antigens: cross-reactions against anti-Cynodon serum. • Pollen antigens: cross-reactions against anti-Zea serum. • Pollen antigens: cross-reactions against anti-Zea serum
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’.