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The grass genera of the world

L. Watson, T.D. Macfarlane, and M.J. Dallwitz

Centotheca Desv.

From the Greek centein (to prick) and theke (the box), referring to prickly hairs within the spikelet (on the upper lemmas).

Type species: Type: C. lappacea (L.) Desv.

Including Centosteca Desv., Ramosia Merr.

Habit, vegetative morphology. Perennial; rhizomatous, or caespitose. The flowering culms leafy. Culms 25–125 cm high; woody and persistent (at base). Culm nodes glabrous. Culm internodes solid. Plants unarmed. Leaves not basally aggregated; auriculate, or non-auriculate; without auricular setae. Leaf blades broadly linear to lanceolate; broad; pseudopetiolate to not pseudopetiolate; cross veined, or without cross venation (rarely); disarticulating from the sheaths, or persistent. Ligule an unfringed membrane.

Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. Viviparous, or not viviparous.

Inflorescence. Inflorescence determinate; paniculate, or of spicate main branches; open; espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets not secund; pedicellate.

Female-fertile spikelets. Spikelets compressed laterally; disarticulating above the glumes (usually), or falling with the glumes; usually but tardily disarticulating between the florets; with a distinctly elongated rachilla internode between the glumes. Rachilla prolonged beyond the uppermost female-fertile floret; hairy; the rachilla extension with incomplete florets (usually), or naked. Hairy callus absent.

Glumes two; very unequal; shorter than the adjacent lemmas; free (widely separated); pointed; awnless; similar (membranous to herbaceous). Lower glume 3–5 nerved. Upper glume 3–5 nerved. Spikelets with female-fertile florets only, or with incomplete florets (usually with a rudimentary floret, and the upper ‘fertile’ florets sometimes female-only). The incomplete florets distal to the female-fertile florets. The distal incomplete florets usually 1. Spikelets without proximal incomplete florets.

Female-fertile florets (1–)2–3 (C. uniflora being 1-flowered). Lemmas not becoming indurated; entire to incised (obtuse to emarginate); mucronate; hairy (the upper lemmas with reflexed hairs); carinate; 9 nerved. Palea present; awnless, without apical setae; 2-nerved. Lodicules present, or absent; when present, 2; free; fleshy; glabrous. Stamens 2–3. Anthers not penicillate. Ovary apically glabrous; without a conspicuous apical appendage. Styles free to their bases. Stigmas 2.

Fruit, embryo and seedling. Fruit free from both lemma and palea; small; compressed laterally. Hilum short. Embryo small. Endosperm containing only simple starch grains. Embryo with an epiblast; with a scutellar tail; with an elongated mesocotyl internode. Embryonic leaf margins meeting, or overlapping.

Seedling with a short mesocotyl. First seedling leaf with a well-developed lamina. The lamina broad; supine; 6–12 veined.

Abaxial leaf blade epidermis. Papillae absent. Mid-intercostal long-cells having markedly sinuous walls (thin walled). Microhairs present; panicoid-type; 31–36(–44) microns long. Microhair apical cells 18–22 microns long. Microhair apical cell/total length ratio 0.6. Stomata common; 30–36 microns long. Subsidiaries triangular. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells common to absent or very rare; when present, in cork/silica-cell pairs; silicified. Intercostal silica bodies when present, cross-shaped. Costal short-cells conspicuously in long rows. Costal silica bodies ‘panicoid-type’; cross shaped, or butterfly shaped, or dumb-bell shaped.

Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with adaxial palisade; without arm cells; with fusoids, or without fusoids. The fusoids an integral part of the PBS. Leaf blade ‘nodular’ in section (rarely), or adaxially flat. Midrib conspicuous; with one bundle only. Bulliforms present in discrete, regular adaxial groups; in simple fans (the groups large and wide, and sometimes some irregular groups). All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present; forming ‘figures’. Sclerenchyma all associated with vascular bundles.

Cytology. Chromosome base number, x = 12. 2n = 24. 2 ploid.

Classification. Watson & Dallwitz (1994): Centothecoideae; Centotheceae. Soreng et al. (2015): Panicoideae; Centotheceae. 4 species.

Distribution, phytogeography, ecology. Tropical Africa, Asia, Polynesia.

Shade species; glycophytic. Forests.

Economic aspects. Significant weed species: C. lappacea (in North America).

Rusts and smuts. Rusts — Puccinia.

References, etc. Leaf anatomical: Metcalfe 1960; studied by us - C. lappacea (L.) Desvaux.

Illustrations. • C. lappacea: Kunth (1835). • C. lappacea: Fl. W. Trop. Afr. (1936)

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.’.