The grass genera of the world
Habit, vegetative morphology. Perennial; often stoloniferous. Culms 20–100 cm high; herbaceous. Plants unarmed. Leaves non-auriculate (but with conspicuous hairs above the ligule). Leaf blades without abaxial multicellular glands; without cross venation; persistent. Ligule a fringed membrane to a fringe of hairs.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets.
Inflorescence. Inflorescence of spicate main branches (several slender spikes, usually on a long axis); digitate, or subdigitate, or non-digitate. Rachides flattened. Inflorescence espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes spikes; with substantial rachides (these zigzag, flattened); disarticulating (in C. africana, the peduncle bears a cupular disarticulation zone at the point of origin of the spikes, which seem to fall together), or persistent (?); if disarticulating, falling entire. Spikelets solitary; secund; biseriate.
Female-fertile spikelets. Spikelets about 3 mm long; adaxial; compressed dorsiventrally; disarticulating above the glumes. Rachilla terminated by a female-fertile floret. Hairy callus absent.
Glumes two; more or less equal; long relative to the adjacent lemmas (the upper considerably exceeding them); dorsiventral to the rachis; hairless; glabrous; pointed (acute); awnless; carinate (G1, asymmetrically so), or non-carinate (G2); (the lower) with the keel conspicuously winged; very dissimilar (both long, membranous, the lower asymmetrically 1-keeled, the upper flat-backed, infolded with two keels). Lower glume G2 two-keeled; 0–1 nerved. Upper glume 1–3 nerved. Spikelets with female-fertile florets only; without proximal incomplete florets.
Female-fertile florets 1. Lemmas less firm than the glumes (hyaline); not becoming indurated; awnless to mucronate; hairy (long-hairy on the veins); weakly carinate; without a germination flap; 3 nerved. Palea present; relatively long; apically notched; awnless, without apical setae; textured like the lemma; not indurated; 2-nerved; keel-less. Lodicules present; 2; free; fleshy; glabrous; not or scarcely vascularized. Stamens 3. Anthers not penicillate; without an apically prolonged connective. 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); obovoid. Hilum short. Pericarp fused. Embryo large.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells of similar wall thickness costally and intercostally. Mid-intercostal long-cells having markedly sinuous walls. Microhairs present; more or less spherical to elongated; clearly two-celled; chloridoid-type (but with an unusual apical, peg-like appendage). Microhair apical cell wall of similar thickness/rigidity to that of the basal cell. Microhairs 15–21 microns long. Microhair basal cells 9–12 microns long. Microhairs (4.5–)7.5 microns wide at the septum. Microhair total length/width at septum 2–3.3. Microhair apical cells 7.5–11 microns long. Microhair apical cell/total length ratio 0.45–0.6. Stomata common; 19.5–21 microns long. Subsidiaries mostly low dome-shaped. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells common; in cork/silica-cell pairs and not paired; not silicified. Intercostal silica bodies absent. Costal short-cells conspicuously in long rows. Costal silica bodies present in alternate cell files of the costal zones; panicoid-type; consistently dumb-bell shaped.
Transverse section of leaf blade, physiology. Lamina mid-zone in transverse section open.
C4; XyMS+. PCR sheaths of the primary vascular bundles interrupted; interrupted abaxially only. PCR sheath extensions absent. PCR cell chloroplasts centripetal. Mesophyll traversed by columns of colourless mesophyll cells (in places, but most of the columns terminate one cell short of the abaxial epidermis). Leaf blade nodular in section to adaxially flat. Midrib not readily distinguishable; with one bundle only. Bulliforms present in discrete, regular adaxial groups; associated with colourless mesophyll cells to form deeply-penetrating fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present; forming figures (all bundles with anchor-shaped combined girders). Sclerenchyma all associated with vascular bundles. The lamina margins with fibres.
Cytology. 2n = 27.
Classification. Watson & Dallwitz (1994): Chloridoideae; main chloridoid assemblage. Soreng et al. (2015): Chloridoideae; Cynodonteae; Farragininae. 5–6 species.
Distribution, phytogeography, ecology. Tropical Africa, North and South America.
Mesophytic to xerophytic; species of open habitats; glycophytic. Sandy savanna.
References, etc. Leaf anatomical: this project.
Illustrations. • C. africana: Hook. Ic. Pl. 24 (1895)
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’.