The grass genera of the world
Habit, vegetative morphology. Annual (or short-lived); loosely caespitose. Culms 30–80 cm high; herbaceous. Leaves not basally aggregated. Leaf blades lanceolate; narrow; 3–7 mm wide; without cross venation; persistent.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets.
Inflorescence. Inflorescence paniculate; open; with capillary branchlets; espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes persistent. Spikelets not secund; not two-ranked; pedicellate. Pedicel apices oblique.
Female-fertile spikelets. Spikelets 2.2–2.8 mm long; compressed dorsiventrally; falling with the glumes. The upper floret not stipitate. Rachilla terminated by a female-fertile floret.
Glumes two; very unequal; (the upper) about equalling the spikelets; (the upper) long relative to the adjacent lemmas; hairless; not pointed; awnless; non-carinate. Lower glume about 0.25 times the length of the upper glume; 3–5 nerved. Upper glume 5 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; becoming conspicuously hardened and enlarged laterally. The proximal lemmas two-keeled, sulcate and nerveless between them; awnless; 4 nerved; slightly exceeded by the female-fertile lemmas; less firm than the female-fertile lemmas (membranous); not becoming indurated.
Female-fertile florets 1. Lemmas papillose; not becoming indurated; pallid; entire (and apiculate); awnless; hairless; non-carinate; having the margins inrolled against the palea. Palea present; relatively long; tightly clasped by the lemma; awnless, without apical setae; textured like the lemma.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells markedly different in shape costally and intercostally (the costals much narrower); of similar wall thickness costally and intercostally (thin walled). Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs present; elongated; clearly two-celled; panicoid-type. Stomata common. Subsidiaries low dome-shaped. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells common; not paired (solitary, rectangular, often large); not silicified. Costal short-cells conspicuously in long rows. Costal silica bodies panicoid-type; butterfly shaped to nodular (ranging from short to elongated); not sharp-pointed.
Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll somewhat noticeably, in places, with radiate chlorenchyma; without adaxial palisade; Isachne-type to not Isachne-type. Leaf blade nodular in section to adaxially flat. Midrib conspicuous; with one bundle only, or having a conventional arc of bundles (a large median, with a small bundle on either side which could be considered part of the midrib); with colourless mesophyll adaxially. The lamina symmetrical on either side of the midrib. Bulliforms present in discrete, regular adaxial groups (these wide, one in each of the slight furrows); in simple fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present (primaries only); forming figures (the midrib median and some other primaries with anchors). Sclerenchyma all associated with vascular bundles.
Classification. Watson & Dallwitz (1994): Panicoideae; Panicodae; Paniceae. Soreng et al. (2015): Panicoideae; Panicodae; Paspaleae; Otachyriinae. 1 species (P. tenella).
Distribution, phytogeography, ecology. Brazil.
Mesophytic; shade species; glycophytic.
References, etc. Morphological/taxonomic: Renvoize (1982), Kew Bull. 37, 323. Leaf anatomical: studied by us.
Special comments. Fruit data wanting.
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’.