The grass genera of the world
Including Pithecurus Kunth, Schizopogon Spreng.
Habit, vegetative morphology. Annual, or perennial; rhizomatous, or stoloniferous, or caespitose, or decumbent. Culms (5–)30–320 cm high; woody and persistent (rarely, and never tall), or herbaceous; sparsely to amply branched above (mostly), or unbranched above. The branching simple. Culm internodes solid, or hollow. Leaves not basally aggregated; non-auriculate. Leaf blades linear; narrow; without cross venation; persistent; once-folded in bud. Ligule present; a fringed membrane (short).
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. The spikelets of sexually distinct forms on the same plant; hermaphrodite and male-only, or hermaphrodite and sterile; overtly heteromorphic; all in heterogamous combinations. Plants exposed-cleistogamous, or chasmogamous.
Inflorescence. Inflorescence a single raceme, or paniculate (of single racemes, these sometimes solitary but usually in a spatheate false panicle). Rachides flattened. Inflorescence spatheate; a complex of partial inflorescences and intervening foliar organs. Spikelet-bearing axes peduncled racemes; solitary (in their spathes, but often fascicled); with substantial rachides; disarticulating; disarticulating at the joints. Articles non-linear (compressed, thickened above with a cupular, usually fringed apex); with toothed apices. Spikelets paired; secund; sessile and pedicellate; consistently in long-and-short combinations; in pedicellate/sessile combinations. Pedicels of the pedicellate spikelets free of the rachis. The shorter spikelets hermaphrodite. The longer spikelets male-only, or sterile.
Female-sterile spikelets. The pedicellate (male or sterile) members broader and flatter or reduced, their lower glume sometimes awned.
Female-fertile spikelets. Spikelets compressed dorsiventrally (or subterete below and compressed between the internode and the pedicel, lanceolate to linear); falling with the glumes (and the joint). Rachilla terminated by a female-fertile floret. Hairy callus present. Callus short; blunt.
Glumes present; two; more or less equal; long relative to the adjacent lemmas; awned (the upper, rarely), or awnless; very dissimilar (the lower bicarinate, the upper thinner and naviculate). Lower glume two-keeled (the keels not winged, but excurrent as teeth or mucros); convex on the back to flattened on the back; not pitted; relatively smooth; 3–13 nerved (with several between the keels). Upper glume 1–3 nerved. Spikelets with incomplete florets. The incomplete florets proximal to the female-fertile florets. The proximal incomplete florets 1; epaleate; sterile. The proximal lemmas awnless; 2 nerved; similar in texture to the female-fertile lemmas (hyaline, often purple); not becoming indurated.
Female-fertile florets 1. Lemmas often stipitiform; less firm than the glumes (hyaline); not becoming indurated; usually incised (rarely merely prolonged into the awn, without teeth); when incised, 2 lobed; deeply cleft (often deeply bifid), or not deeply cleft; awned. Awns 1; median; from a sinus, or apical; geniculate; hairless (glabrous); about as long as the body of the lemma, or much longer than the body of the lemma (usually short). Lemmas hairless; 1–3 nerved. Palea present, or absent (usually); when present, very reduced (to a minute, hyaline scale); not indurated (hyaline); nerveless. Lodicules present (tiny); 2; fleshy; ciliate, or glabrous. Stamens 2–3. Anthers not penicillate. Ovary apically glabrous. Styles free to their bases. Stigmas 2.
Fruit, embryo and seedling. Fruit free from both lemma and palea; compressed dorsiventrally (or subterete). Hilum short. Embryo large. Endosperm hard; without lipid. Embryo without an epiblast; with a scutellar tail; with an elongated mesocotyl internode. Embryonic leaf margins overlapping.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells of similar wall thickness costally and intercostally (quite thin walled). Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs present; panicoid-type; (36–)42–50(–60) microns long; 6–8.4 microns wide at the septum. Microhair total length/width at septum 5.2–7. Microhair apical cells (18–)19–26(–30) microns long. Microhair apical cell/total length ratio 0.46–0.52. Stomata common; (25–)27–29(–30) microns long. Subsidiaries low to high dome-shaped to triangular. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells absent or very rare. Costal short-cells conspicuously in long rows. Costal silica bodies panicoid-type; dumb-bell shaped (mostly, long to short), or nodular (some); not sharp-pointed.
Transverse section of leaf blade, physiology. C4; biochemical type NADPME (1 species); XyMS. PCR sheath outlines uneven. PCR cell chloroplasts centrifugal/peripheral. Mesophyll with radiate chlorenchyma, or with non-radiate chlorenchyma. Leaf blade adaxially flat. Midrib conspicuous; having a conventional arc of bundles; with colourless mesophyll adaxially, or without colourless mesophyll adaxially. Bulliforms not present in discrete, regular adaxial groups (the adaxial epidermis of some species with scattered bulliform cells, S. fragile having the adaxial epidermis largely bulliform and a large fan of bulliforms over the midrib). Many of the smallest vascular bundles unaccompanied by sclerenchyma. Combined sclerenchyma girders present; forming figures (some of the primary laterals with anchors or Is). Sclerenchyma all associated with vascular bundles.
Culm anatomy. Culm internode bundles in three or more rings.
Phytochemistry. Leaves without flavonoid sulphates (3 species).
Cytology. Chromosome base number, x = 5 and 10. 2n = 20, 30, 40, and 50.
Classification. Watson & Dallwitz (1994): Panicoideae; Andropogonodae; Andropogoneae; Andropogoninae. Soreng et al. (2015): Panicoideae; Andropogonodae; Andropogoneae; Andropogoninae. About 60 species.
Distribution, phytogeography, ecology. Tropical.
Helophytic, or mesophytic, or xerophytic; species of open habitats; halophytic (rarely), or glycophytic. Savanna, rarely sandy beaches or dunes.
Economic aspects. Significant weed species: S. condensatum, S. scoparium. Important native pasture species: S. brevifolium, S. sanguineum.
Rusts and smuts. Rusts Puccinia. Taxonomically wide-ranging species: Uromyces clignyi. Smuts from Ustilaginaceae. Ustilaginaceae Sorosporium and Sphacelotheca.
References, etc. Leaf anatomical: Metcalfe 1960 (S. jeffreysii); studied by us - S. fragile; C.B. de Yong, pers. comm. (S. exile, S. sanguineum).
Illustrations. • S. tenerum, as Andropogon tener: Kunth (1835). • S. pachyarthron, S. pseudoeulalia: Gardner, 1952. • S. sanguineum, as Andropogon hirtiflorus: Kunth (1835). • General aspect (S. sanguineum): 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’.