The grass genera of the world
~ Panicum discrepans Döll.
Type species: C. discrepans (Döll.) Zuloaga & Morrone.
Habit, vegetative morphology. Perennial; shortly rhizomatous and decumbent. The flowering culms leafy. Culms 20–40 cm high; mostly unbranched above. Culm nodes dark, glabrous. Culm internodes hollow. Leaf blades apically acute, lanceolate; narrow; 2–15 cm long, 2–6 mm wide. Ligule a fringe of hairs (whitish); 3–4 mm long.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. The spikelets hermaphrodite.
Inflorescence. Inflorescence paniculate; contracted; non-digitate. Primary inflorescence branches inserted all around the main axis. Inflorescence espatheate. Spikelet-bearing axes persistent. Spikelets unaccompanied by bractiform involucres, not associated with setiform vestigial branches; shortly pedicellate.
Female-fertile spikelets. Spikelets 1.1–1.3 mm long; ovoid; gibbous, not noticeably compressed to compressed dorsiventrally; planoconvex; falling with the glumes. Rachilla terminated by a female-fertile floret.
Glumes present; one per spikelet, or two; when both present, very unequal; (the upper ones) about equalling the spikelets to exceeding the spikelets; long relative to the adjacent lemmas; awnless; when both present, very dissimilar. Lower glume when present, shorter than the lowest lemma; when present, 0 nerved. Upper glume gibbous, blunt or acute, 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 resembling the upper glume; awnless; 3 nerved; more or less equalling the female-fertile lemmas (slightly longer).
Female-fertile florets 1. Lemmas ovoid, gibbous, open at the apex; decidedly firmer than the glumes; becoming indurated; entire; pointed; not deeply cleft; awnless; hairy (with long, whitish curled hairs at base and apex); non-carinate; having the margins inrolled against the palea; 3 nerved. Palea present. Lodicules present; 2; fleshy. Stamens 3.
Fruit, embryo and seedling. Fruit broadly ovoid. Hilum short.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells markedly different in shape costally and intercostally (the costals narrower, more elongate-rectangular); of similar wall thickness costally and intercostally. Mid-intercostal long-cells rectangular and fusiform; having markedly sinuous walls. Microhairs present; elongated; clearly two-celled; panicoid-type. Microhair apical cell wall thinner than that of the basal cell and often collapsed, or thinner than that of the basal cell but not tending to collapse. Microhair apical cell/total length ratio 0.3–0.7. Stomata common; 32.5–39 microns long. Subsidiaries non-papillate; dome-shaped. Intercostal short-cells common; in cork/silica-cell pairs and not paired (some solitary). Macrohairs sometimes present intercostally. Costal short-cells conspicuously in long rows. Costal silica bodies present and well developed; panicoid-type; butterfly shaped and dumb-bell shaped.
Transverse section of leaf blade, physiology. Lamina mid-zone in transverse section open.
C4; XyMS. PCR sheath extensions absent. Mesophyll without adaxial palisade. Leaf blade adaxially flat. Midrib not readily distinguishable; with one bundle only. The lamina symmetrical on either side of the midrib. Bulliforms present in discrete, regular adaxial groups; in simple fans. Many of the smallest vascular bundles unaccompanied by sclerenchyma. Combined sclerenchyma girders present (with first order bundles only); nowhere forming figures. Sclerenchyma all associated with vascular bundles. The lamina margins with fibres (in the form of minute caps).
Classification. Watson & Dallwitz (1994): not described separately. Soreng et al. (2015): Panicoideae; Panicodae; Paspaleae; Arthropogoninae. 1 species (C. discrepans).
Distribution, phytogeography, ecology. From Cuba and Belize to central Brazil.
Helophytic; species of open habitats. In seasonally flooded fields and edges of swamps, in sandy or rocky soils.
References, etc. Morphological/taxonomic: Morrone, O., Scataglini, M.A. & Zuloaga, F.O. (2007). Cyphonanthus, a new genus segregated from Panicum (Poaceae: Panicoideae: Paniceae) based on morphological, anatomical and molecular data. TAXON 56(2), 521532. Leaf anatomical: Morrone et al. (2007).
Illustrations. • C. discrepans (as Panicum: R. Pohl, Flora Costaricensis (1980)
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’.