The grass genera of the world
Habit, vegetative morphology. Erect perennial; not reedy; sometimes rhizomatous. Culms 100–400 cm high; herbaceous; unbranched above. Leaf blades linear; broad to narrow; flat, or acicular; pseudopetiolate (attenuate to the sheath), or not pseudopetiolate; without cross venation. Ligule an unfringed membrane.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. The spikelets all alike in sexuality; homomorphic.
Inflorescence. Inflorescence of spicate main branches, or paniculate (the panicle often large, branched, silky, red or brown, the central axis longer and the racemes shorter than in Miscanthus sensu stricto); open, or contracted; non-digitate; espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes racemes (slender, flexuous); with very slender rachides; ultimately disarticulating; tardily disarticulating at the joints. Articles linear; not appendaged; disarticulating transversely. Spikelets paired; pedicellate; consistently in long-and-short combinations; unequally pedicellate in each combination. Pedicels of the pedicellate spikelets free of the rachis. The shorter spikelets hermaphrodite. The longer spikelets hermaphrodite.
Female-fertile spikelets. Spikelets compressed dorsiventrally; falling with the glumes (disarticulating from the pedicels before break-up of the rachis). Rachilla terminated by a female-fertile floret. Hairy callus present (spikelets with an involucre of very long hairs at the base). Callus blunt.
Glumes two; more or less equal; long relative to the adjacent lemmas; awnless; carinate (G2), or non-carinate (G1); very dissimilar (papery to leathery, the G1 flat-backed, 2-keeled with inflexed margins and nerves between the keels, the G2 naviculate). Lower glume two-keeled; flattened on the back; not pitted; relatively smooth; vein number variable. Upper glume 1 nerved, or 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; epaleate; sterile. The proximal lemmas awnless (muticous or mucronate); similar in texture to the female-fertile lemmas (hyaline); not becoming indurated.
Female-fertile florets 1. Lemmas less firm than the glumes (hyaline); not becoming indurated; entire (seemingly); not deeply cleft; awned. Awns 1; median; apical; geniculate (twisted, slightly bent); about as long as the body of the lemma to much longer than the body of the lemma. Lemmas hairy (marginally); non-carinate; without a germination flap. Palea present; conspicuous but relatively short; entire; awnless, without apical setae (ciliate); not indurated (hyaline); nerveless; keel-less. Lodicules present; 2; free; fleshy. Stamens 3. Stigmas 2.
Fruit, embryo and seedling. Hilum short. Embryo large; without a scutellar tail.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae present (in M. sorghum), or absent; intercostal. Intercostal papillae over-arching the stomata; consisting of one oblique swelling per cell (elongated, almost clavate, thick walled). Mid-intercostal long-cells having straight or only gently undulating walls (in M. sorghum), or having markedly sinuous walls. Microhairs present (though none seen in M. sorghum, where the intercostal zones are extensively obscured by prickles and papillae); panicoid-type; (34–)36–42(–44) microns long. Microhair apical cells 13–22 microns long. Microhair apical cell/total length ratio 0.49. Stomata common. Subsidiaries non-papillate; low dome-shaped, or triangular (mostly domes in M. sorghum). Intercostal short-cells absent or very rare. Costal short-cells predominantly paired and neither distinctly grouped into long rows nor predominantly paired (mostly solitary and paired, but the costal long-cells sometimes rather short, giving the appearance of long rows). Costal silica bodies panicoid-type; cross shaped to dumb-bell shaped, or nodular (a few); not sharp-pointed.
Transverse section of leaf blade, physiology. Leaf blades consisting of midrib (in M. teretifolium, where the centre consists wholly of colourless tissue, with the chlorenchyma and vbs confined to the peripheral zone), or laminar.
C4; XyMS. PCR sheath outlines uneven. PCR cell chloroplasts centrifugal/peripheral. Leaf blade of M. sorghum nodular in section; with the ribs very irregular in sizes (in M. sorghum, especially near the midrib). Midrib conspicuous (or the blade reduced to the midrib); in M. sorghum having a conventional arc of bundles; with colourless mesophyll adaxially (at least in the lower part of the blade). Bulliforms present in discrete, regular adaxial groups (these large, in each furrow), or not present in discrete, regular adaxial groups (M. teretifolium); in simple fans and associated with colourless mesophyll cells to form deeply-penetrating fans (the fans in M. sorghum, more or less deformed); associating with colourless mesophyll cells to form arches over small vascular bundles. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present, or absent (abaxial girders only in M. teretifolium); in M. sorghum forming figures (the large bundles with massive Ts or Is). Sclerenchyma all associated with vascular bundles.
Cytology. Chromosome base number, x = 15. 2n = 28 and 30. 2 ploid.
Classification. Watson & Dallwitz (1994): Panicoideae; Andropogonodae; Andropogoneae; Andropogoninae. Soreng et al. (2015): Panicoideae; Andropogonodae; Andropogoneae; Saccharinae. 6–7 species.
Distribution, phytogeography, ecology. Tropical and southern Africa.
Helophytic; shade species, or species of open habitats; glycophytic. Streamsides and forest margins.
Hybrids. Intergeneric hybrids procured with Saccharum.
References, etc. Leaf anatomical: Metcalfe 1960 and this project.
Illustrations. • M. junceus, as M. teretifolium: Hook. Ic. Pl. 31 (1922). • M. violaceum: Jacques-Félix, 1962. • M. sorghum, abaxial epidermis of 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’.