The grass genera of the world
Type species: Type: P. brunoniana (Griff.) Griff.
Habit, vegetative morphology. Perennial; decumbent. Culms herbaceous; branched above. The branching simple. Culm nodes glabrous. Culm leaf sheaths compressed. Culm internodes hollow. Leaves not basally aggregated; non-auriculate. Sheath margins free. The sheaths flattened. Leaf blades narrow; not setaceous; flat (glabrous); without cross venation; disarticulating from the sheaths, or persistent. Ligule an unfringed membrane.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets (rarely), or without hermaphrodite florets.
Inflorescence. Inflorescence of spicate main branches (the slender flexuous branches sometimes reduced to one or two spikelets); non-digitate. Primary inflorescence branches inserted all around the main axis. Inflorescence axes not ending in spikelets (the racemes each terminated by a stiff bristle at least as long as the uppermost spikelet). Inflorescence espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes very much reduced (with only one spikelet), or racemes (with a compressed peduncle, the few spikelets distant); persistent. Spikelets solitary; not secund; shortly pedicellate. Pedicel apices truncate, or discoid.
Female-fertile spikelets. Spikelets 6–10 mm long; lanceolate; abaxial; compressed dorsiventrally; falling with the glumes; with distinctly elongated rachilla internodes between the florets. The upper floret conspicuously stipitate. The stipe beneath the upper floret not filiform. Rachilla terminated by a female-fertile floret.
Glumes two; very unequal; (the longer) long relative to the adjacent lemmas; awned, or awnless (G2 acuminate to awnlike above); very dissimilar (lower tiny, semiorbicular, rectangular or broadly obovate, the upper lanceolate, acuminate or tapering into an awn). Lower glume 0 nerved. Upper glume 5–9 nerved. Spikelets with incomplete florets (the lower floret male, the upper female or rarely hermaphrodite). 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. The proximal incomplete florets male. The proximal lemmas awnless, or awned (sometimes awnlike above); 7–13 nerved; decidedly exceeding the female-fertile lemmas (similar to the G2 in shape); less firm than the female-fertile lemmas to similar in texture to the female-fertile lemmas; not becoming indurated.
Female-fertile florets 1. Lemmas similar in texture to the glumes to decidedly firmer than the glumes; smooth; becoming indurated (slightly), or not becoming indurated; white in fruit; entire; awnless; hairless; non-carinate; having the margins lying flat on the palea; 0 nerved. Palea present (oblong); relatively long; obscurely nerved. Lodicules present; 2; joined, or free; fleshy; glabrous; not toothed. Stamens 3, or 0 (usually rudimentary or missing). Anthers not penicillate. Ovary apically glabrous (shortly stipitate). Styles fused, or free to their bases (rarely).
Fruit, embryo and seedling. Fruit small; compressed dorsiventrally. Hilum short. Embryo large.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae present; costal and intercostal. Intercostal papillae over-arching the stomata; consisting of one symmetrical projection per cell. Long-cells similar in shape costally and intercostally; of similar wall thickness costally and intercostally. Intercostal zones exhibiting many atypical long-cells to without typical long-cells (the long-cells mostly short-rectangular). Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs present; elongated; clearly two-celled; panicoid-type; (31.5–)33–39 microns long (P. paradoxa), or 22–24 microns long (P. spinescens); (6–)6.3–7.2(–8.4) microns wide at the septum (P. paradoxa), or 6.6–7.5 microns wide at the septum (P. spinescens). Microhair total length/width at septum 4.6–6.5 (P. paradoxa), or 3–3.6 (P. spinescens). Microhair apical cells (14.4–)15.6–18.6(–19.5) microns long (P. paradoxa), or 10.2–10.5 microns long (P. spinescens). Microhair apical cell/total length ratio 0.46–0.59 (P. paradoxa), or 0.4–0.47 (P. spinescens). Stomata common; 19–29 microns long. Subsidiaries low to high dome-shaped. Guard-cells overlapped by the interstomatals. Intercostal short-cells absent or very rare. Costal short-cells neither distinctly grouped into long rows nor predominantly paired. Costal silica bodies horizontally-elongated crenate/sinuous (a few, in P. spinescens), or panicoid-type (predominating, mostly rather angular, with truncated points); not sharp-pointed.
Transverse section of leaf blade, physiology. C4; XyMS. Mesophyll with radiate chlorenchyma. Leaf blade adaxially flat. Midrib conspicuous to not readily distinguishable; having a conventional arc of bundles; with colourless mesophyll adaxially to without colourless mesophyll adaxially. Bulliforms present in discrete, regular adaxial groups, or not present in discrete, regular adaxial groups (the epidermis irregularly bulliform, e.g. P. paradoxa); in P. spinescens in simple fans (these large, Zea-type, over the minor bundles). Many of the smallest vascular bundles unaccompanied by sclerenchyma. Combined sclerenchyma girders present; nowhere forming figures. Sclerenchyma all associated with vascular bundles.
Cytology. Chromosome base number, x = 8. 2n = 16.
Classification. Watson & Dallwitz (1994): Panicoideae; Panicodae; Paniceae. Soreng et al. (2015): Panicoideae; Panicodae; Paniceae; Cenchrinae. 6 species.
Distribution, phytogeography, ecology. India & Japan to Australia.
Hydrophytic to helophytic; species of open habitats. Marshes.
Rusts and smuts. Smuts from Ustilaginaceae. Ustilaginaceae Sorosporium and Sphacelotheca.
References, etc. Morphological/taxonomic: Vickery 1952; Webster 1987. Leaf anatomical: this project.
Illustrations. • P. paradoxa, as Panicum: Kunth (1835). • General aspect, inflorescence (P. abortiva): E. Hickman. • P. abortiva: Gardner, 1952. • P. spinescens, abaxial epidermis of leaf blade: this project. • P. spinescens, abaxial epidermis of leaf blade: this project. • P. spinescens, T.S. leaf blade midrib zone: this project. • P. spinescens, T.S. leaf blade lateral part: this project. • P. abortiva, T.S. leaf blade lateral part: 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’.