The grass genera of the world
Habit, vegetative morphology. Annual, or perennial; stoloniferous (each stolon being a single, bare internode), or caespitose, or decumbent. Culms 8–80 cm high; herbaceous; branched above, or unbranched above. Culm nodes glabrous. Culm internodes solid. Plants unarmed. Young shoots intravaginal. Leaves not basally aggregated; non-auriculate. Leaf blades narrow; 2–7 mm wide (their margins thickened, with tubercle-based hairs); somewhat cordate; flat, or rolled (convolute); without abaxial multicellular glands; not pseudopetiolate; without cross venation; persistent. Ligule a fringed membrane; 1 mm long. Contra-ligule absent.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. The spikelets of sexually distinct forms on the same plant; hermaphrodite and sterile (there being 1–3 sterile spikelets at the tips of the reduced inflorescence branches); overtly heteromorphic (the sterile spikelets more or less awn-like); all in heterogamous combinations.
Inflorescence. Inflorescence bristly, a false spike, with spikelets on contracted axes. Inflorescence axes not ending in spikelets (but rather, ending in bristles representing the uppermost 1–3 spikelets). Inflorescence espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes very much reduced (to shortly pedunculate spikelet clusters); disarticulating; falling entire (i.e., the clusters shed). Spikelets unaccompanied by bractiform involucres, not associated with setiform vestigial branches; solitary; not secund; sessile to pedicellate; imbricate.
Female-sterile spikelets. The sterile spikelets awnlike, at the tips of the reduced branches.
Female-fertile spikelets. Spikelets 3–4 mm long; adaxial; compressed dorsiventrally; planoconvex; falling with the glumes (in the glomerules); with conventional internode spacings. Rachilla terminated by a female-fertile floret. Hairy callus present (at the base of the cluster). Callus long (formed from the rachis base); blunt.
Glumes one per spikelet (G1 sometimes absent), or two; (the upper) relatively large; very unequal; (the upper) long relative to the adjacent lemmas; hairy; (the upper) awned (with a slightly recurved awn at least as long as itself); non-carinate; very dissimilar (G1 reduced to a minute scale, G2 flat, elliptic-lanceolate, herbaceous). Lower glume much shorter than half length of lowest lemma (minute); 0 nerved. Upper glume 5–7 nerved. Spikelets with female-fertile florets only.
Female-fertile florets 1. Lemmas less firm than the glumes (membranous); not becoming indurated; entire to incised; pointed; when incised, minutely 3 lobed; not deeply cleft; mucronate to awned (from the mid-nerve). Awns when present, 1; median; apical; non-geniculate; hairless (scaberulous); much shorter than the body of the lemma; entered by one vein. Lemmas sparsely hairy; non-carinate; without a germination flap; 3 nerved. Palea present (broadly lanceolate); relatively long; entire (truncate); awnless, without apical setae (with scattered hairs); slightly thinner than the lemma; not indurated; 2-nerved; 2-keeled. Lodicules present; 2; free; fleshy; glabrous; not or scarcely vascularized. Stamens 3. Anthers 2 mm long; not penicillate; without an apically prolonged connective. Ovary apically glabrous. Styles free to their bases. Stigmas 2; red pigmented.
Fruit, embryo and seedling. Fruit free from both lemma and palea; small (2 mm long); ellipsoid; compressed dorsiventrally (dorsally). Hilum short (elliptical). Pericarp fused. Embryo large (about 1/3 the length of the fruit); not waisted.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae present; intercostal. Intercostal papillae consisting of one oblique swelling per cell (at one end of each interstomatal cell). Long-cells differing markedly in wall thickness costally and intercostally (intercostal walls thicker). Mid-intercostal long-cells rectangular (very); having markedly sinuous walls. Microhairs present; elongated; clearly two-celled; chloridoid-type. Microhair apical cell wall of similar thickness/rigidity to that of the basal cell. Microhairs (39–)42–45(–51) microns long. Microhair basal cells 33 microns long. Microhairs 12–14.4 microns wide at the septum. Microhair total length/width at septum 2.9–4.3. Microhair apical cells (9–)10.5–12(–15) microns long. Microhair apical cell/total length ratio 0.23–0.33. Stomata common; 27–33 microns long. Subsidiaries dome-shaped and triangular. Guard-cells stomata sunken below the raised (concave) ends of the interstomatals, but not overlapped. Intercostal short-cells absent or very rare. Intercostal silica bodies absent. Costal short-cells conspicuously in long rows (but the short-cells often rather long, giving an impression of some pairs and short rows). Costal silica bodies present in alternate cell files of the costal zones; almost exclusively saddle shaped; not sharp-pointed.
Transverse section of leaf blade, physiology. Lamina mid-zone in transverse section open.
C4; XyMS+. PCR sheath outlines even. PCR sheaths of the primary vascular bundles complete to interrupted; interrupted adaxially only. PCR sheath extensions absent. PCR cell chloroplasts centripetal. Leaf blade adaxially flat (with low abaxial ribs). Midrib not readily distinguishable; with one bundle only. Bulliforms present in discrete, regular adaxial groups; in simple fans (the large median cells deeply penetrating), or associated with colourless mesophyll cells to form deeply-penetrating fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present (with the primaries - some minor bundles with strands only); forming figures. 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; Traginae. 2 species.
Distribution, phytogeography, ecology. Southwest Africa to southern Angola.
Xerophytic; species of open habitats; glycophytic. In seasonally moist locations?.
References, etc. Leaf anatomical: Metcalfe 1960; studied by us - M. luderitzianum Hack.; photos of M. luderitzianum provided by R.P. Ellis.
Illustrations. • General aspect (M. luederitzianum): 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: 11th December 2017. delta-intkey.com/grass’.