The grass genera of the world
Habit, vegetative morphology. Annual; caespitose, or decumbent (sometimes rooting at the lower nodes). Culms 15–90 cm high; herbaceous; branched above, or unbranched above. Culm nodes hairy. Culm internodes hollow. Young shoots intravaginal. Leaves not basally aggregated; non-auriculate. Leaf blades linear; narrow; 3–7 mm wide; flat; without cross venation; persistent. Ligule a fringed membrane; not truncate (acute); about 1 mm long (excluding the hairs, which are 1 to 2 mm long). Contra-ligule absent.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets.
Inflorescence. Inflorescence of spicate main branches (spike-like racemes or narrow panicles); subdigitate (usually with several racemes from below the apex), or non-digitate. Primary inflorescence branches (1–)5–8(–15). Inflorescence espatheate; not comprising partial inflorescences and foliar organs. The racemes spikelet bearing to the base. Spikelet-bearing axes persistent. Spikelets paired; secund; pedicellate. Pedicel apices discoid. Spikelets loosely imbricate; consistently in long-and-short combinations (but the spikelets homogamous); unequally pedicellate in each combination. The shorter spikelets hermaphrodite. The longer spikelets hermaphrodite.
Female-fertile spikelets. Spikelets 4–5 mm long; abaxial; compressed dorsiventrally; falling with the glumes; with conventional internode spacings. The upper floret not stipitate. Rachilla terminated by a female-fertile floret. Hairy callus absent. Callus absent.
Glumes two; more or less equal; about equalling the spikelets; long relative to the adjacent lemmas; dorsiventral to the rachis; hairy and hairless; not pointed (obtuse or emarginate); awnless; non-carinate; very dissimilar (the lower hairless, the upper with four dense rows of long, green to dark purple hairs between the veins). Lower glume 5–7 nerved. Upper glume 3 nerved. Spikelets with incomplete florets. The incomplete florets proximal to the female-fertile florets. Spikelets with proximal incomplete florets. The proximal incomplete florets 1; paleate. Palea of the proximal incomplete florets fully developed (two keeled). The proximal incomplete florets male. The proximal lemmas awnless; 3–5 nerved (glabrous on the back, with dense long red-brown hairs at the margins); decidedly exceeding the female-fertile lemmas; less firm than the female-fertile lemmas; becoming indurated (on the margins, remaining membranous on the back).
Female-fertile florets 1. Lemmas decidedly firmer than the glumes; striate; becoming indurated to not becoming indurated (cartilaginous-crustaceous); entire; pointed (acuminate); awnless; hairless; glabrous (smooth and shining); non-carinate; having the margins lying flat on the palea; with a clear germination flap; 3 nerved (the nerves obscure). Palea present; relatively long; entire; awnless, without apical setae; textured like the lemma; indurated; 2-nerved; 2-keeled. Palea keels wingless. Lodicules present; 2; free; fleshy; glabrous; not or scarcely vascularized. Stamens 3. Anthers 3 mm long; not penicillate; without an apically prolonged connective. Ovary apically glabrous. Stigmas 2; red pigmented.
Fruit, embryo and seedling. Fruit free from both lemma and palea; small (almost 2 mm long); compressed dorsiventrally. Hilum short. Embryo large; waisted.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Long-cells markedly different in shape costally and intercostally (the costals much narrower). Mid-intercostal long-cells rectangular and fusiform; having markedly sinuous walls and having straight or only gently undulating walls. Microhairs present; panicoid-type (some quite ordinary, but also with numerous long, narrow, warty macrohairs, many of which appear to have a basal cell); i.e. the normal ones 45–54 microns long; 5.5–7.5 microns wide at the septum. Microhair total length/width at septum 6–10. Microhair apical cells 24–27 microns long. Microhair apical cell/total length ratio 0.5–0.58. Stomata common; 39–45 microns long. Subsidiaries parallel-sided and dome-shaped. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells hair bases impede interpretation; not recordable because macrohair bases impede interpretation. Costal prickles abundant. Crown cells absent. Costal short-cells conspicuously in long rows. Costal silica bodies panicoid-type; short dumb-bell shaped (with sharp points), or cross shaped; sharp-pointed (sharp corners on dumb-bells).
Transverse section of leaf blade, physiology. C4; XyMS. PCR sheath outlines uneven. PCR cell chloroplasts centrifugal/peripheral. Mesophyll with radiate chlorenchyma. Leaf blade nodular in section to adaxially flat; with the ribs more or less constant in size (and slight). Midrib conspicuous; having a conventional arc of bundles; with colourless mesophyll adaxially. Bulliforms present in discrete, regular adaxial groups (in places, but mainly irregularly grouped and constituting most of the epidermis); in simple fans (the more or less irregular fans large), or associated with colourless mesophyll cells to form deeply-penetrating fans; associating with colourless mesophyll cells to form arches over small vascular bundles (especially towards the midrib). Many of the smallest vascular bundles unaccompanied by sclerenchyma. Combined sclerenchyma girders absent. Sclerenchyma all associated with vascular bundles.
Classification. Watson & Dallwitz (1994): Panicoideae; Panicodae; Paniceae. Soreng et al. (2015): Panicoideae; Panicodae; Paniceae; Anthephorinae. 1 species (supposedly 2).
Distribution, phytogeography, ecology. Southern tropical and South Africa.
Mesophytic to xerophytic; shade species, or species of open habitats; glycophytic. In open Acacia and mopane savanna.
References, etc. Morphological/taxonomic: Hubbard 1929. Leaf anatomical: this project; photos of M. albescens provided by R.P. Ellis.
Illustrations. • General aspect (M. albescens): 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’.