The grass genera of the world
Habit, vegetative morphology. Annual, or perennial (with slender culms); caespitose. Culms herbaceous; unbranched above. Culm nodes glabrous. Culm internodes hollow. Leaves mostly basal; non-auriculate. Leaf blades linear; narrow; setaceous (at the tip), or not setaceous; often rolled (involute); without cross venation; persistent. Ligule a fringe of hairs. Contra-ligule absent.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets.
Inflorescence. Inflorescence paniculate; open; espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes persistent. Spikelets in triplets (the triads terminating the panicle branches); not secund; pedicellate (the pedicels free, short); not in distinct long-and-short combinations (?).
Female-fertile spikelets. Spikelets of the triad having their upper glumes backing onto one another; compressed laterally (?); disarticulating above the glumes; with conventional internode spacings. Rachilla terminated by a female-fertile floret. Hairy callus present. Callus short; blunt (or emarginate, or bidentate).
Glumes two; very unequal (G1 shorter, but usually more than half as long as the spikelet); (the upper) long relative to the adjacent lemmas; hairy (often apically penicillate); pointed (lanceolate to linear-lanceolate or acuminate); awnless; non-carinate (dorsally rounded); very dissimilar (G2 much longer, more pointed and less hairy), or similar. Lower glume 3 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 (narrow, with two ciliate keels). The proximal incomplete florets male. The proximal lemmas awnless; 3 nerved; decidedly exceeding the female-fertile lemmas; less firm than the female-fertile lemmas (herbaceous to papery); not becoming indurated.
Female-fertile florets 1. Lemmas less firm than the glumes to decidedly firmer than the glumes; incised (at the summit, the lobes pointed); 2 lobed; deeply cleft (to more than 1/4 of their length), or not deeply cleft; awned. Awns 1; median; from a sinus; geniculate; hairy; much longer than the body of the lemma. Lemmas hairless (always glabrous?); non-carinate; having the margins inrolled against the palea (the palea enclosed save at its summit); with a clear germination flap; 7 nerved. Palea present; apically notched (linear); awnless, without apical setae; 2-nerved; 2-keeled (channelled between the keels). Palea keels wingless. Lodicules present; 2; free; fleshy; glabrous. Stamens 2. 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 (but enclosed); longitudinally grooved. Hilum long-linear. Embryo large.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells similar in shape costally and intercostally; of similar wall thickness costally and intercostally (rather thick walled). Mid-intercostal long-cells rectangular; having markedly sinuous walls (these heavily pitted). Microhairs present; panicoid-type. Stomata common. Subsidiaries consistently low dome-shaped. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells common (very regularly placed between all the long-cells); in cork/silica-cell pairs, or not paired (apparently solitary except when paired with prickle bases). With abundant small, short prickles. Crown cells absent. Costal short-cells conspicuously in long rows. Costal silica bodies panicoid-type; predominantly elongated dumb-bell shaped.
Transverse section of leaf blade, physiology. C4; XyMS. PCR sheath outlines even. PCR cell chloroplasts centrifugal/peripheral. Mesophyll with radiate chlorenchyma; irregularly traversed by columns of colourless mesophyll cells. Leaf blade with distinct, prominent adaxial ribs; with the ribs very irregular in sizes. Midrib not readily distinguishable; with one bundle only. Bulliforms present in discrete, regular adaxial groups (in all the furrows); associated with colourless mesophyll cells to form deeply-penetrating fans; associating with colourless mesophyll cells to form arches over small vascular bundles (many of the bulliform groups associated with deeply penetrating or fully traversing lateral arms of colourless cells). All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present; forming figures (all the larger bundles with massive Is or Ts). Sclerenchyma all associated with vascular bundles.
Special diagnostic feature. The lower glume exceeding the female-fertile lemma.
Classification. Watson & Dallwitz (1994): Panicoideae; cf. Panicodae (as a synonym?); Arundinelleae. Soreng et al. (2015): Panicoideae (as a synonym); Tristachyideae; Trichoneurinae. 5 species.
Distribution, phytogeography, ecology. Tropical Africa, South America.
References, etc. Leaf anatomical: studied by us - D. chrysothrix (= Loudetiopsis).
Illustrations. • D. fulva: Jacques-Félix, 1962
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’.