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The grass genera of the world

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

Imperata Cyr.

Named for sixteenth century Neapolitan naturalist/pharmacist, Ferrante Imperato.

Including Syllepis Fourn.

Habit, vegetative morphology. Perennial; rhizomatous. Culms 10–150 cm high; herbaceous; unbranched above. Culm nodes hairy, or glabrous. Culm internodes solid. Leaves mostly basal; non-auriculate. Leaf blades broad, or narrow; pseudopetiolate (attenuate), or not pseudopetiolate; without cross venation; persistent; rolled in bud. Ligule a fringed membrane.

Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. The spikelets all alike in sexuality; homomorphic.

Inflorescence. Inflorescence paniculate (silky, spiciform or loosely contracted, the branches with numerous short ‘racemes’); contracted; spicate; espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes short ‘racemes’; with very slender rachides; persistent. ‘Articles’ linear; densely long-hairy (the hairs silvery). Spikelets paired; not secund; consistently in ‘long-and-short’ combinations; unequally pedicellate in each combination. Pedicels of the ‘pedicellate’ spikelets free of the rachis. The ‘shorter’ spikelets hermaphrodite. The ‘longer’ spikelets hermaphrodite.

Female-fertile spikelets. Spikelets 2.5–5 mm long; not noticeably compressed to compressed dorsiventrally; falling with the glumes (falling entire from their pedicels). Rachilla terminated by a female-fertile floret. Hairy callus present. The callus hairs white (silky, silvery).

Glumes two; more or less equal; long relative to the adjacent lemmas; without conspicuous tufts or rows of hairs; pointed, or not pointed; awnless; similar (membranous, with long silvery hairs especially towards the base). Lower glume not two-keeled; convex on the back; not pitted; relatively smooth; 5–7 nerved. Upper glume 3–5 nerved. Spikelets with female-fertile florets only (rarely), or with incomplete florets. The incomplete florets proximal to the female-fertile florets. Spikelets with proximal incomplete florets. The proximal incomplete florets 1; paleate (rarely), or epaleate; male (rarely), or sterile. The proximal lemmas awnless; 0 nerved, or 1 nerved; decidedly exceeding the female-fertile lemmas (rarely, the latter may even be absent); similar in texture to the female-fertile lemmas; not becoming indurated.

Female-fertile florets 1. Lemmas lanceolate to oblanceolate, reduced, sometimes absent; less firm than the glumes (hyaline); not becoming indurated; entire, or incised (denticulate); when entire pointed, or blunt; awnless; hairless; non-carinate; 0–1 nerved. Palea present; relatively long, or conspicuous but relatively short, or very reduced (broad); apically notched; awnless, without apical setae; not indurated (hyaline); nerveless. Lodicules absent. Stamens 2 (Section Imperatella), or 1 (Section Eriopogon). Anthers not penicillate. Ovary apically glabrous. Styles fused. Stigmas 2; red pigmented.

Fruit, embryo and seedling. Fruit free from both lemma and palea; small; not noticeably compressed. Hilum short. Embryo large. Endosperm containing only simple starch grains. Embryo without an epiblast; with a scutellar tail; with an elongated mesocotyl internode. Embryonic leaf margins overlapping.

Seedling with a long mesocotyl.

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. Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs present; panicoid-type; (40–)42–54(–60) microns long; 5.4–6 microns wide at the septum. Microhair total length/width at septum 7.8–8.9. Microhair apical cells (16.5–)18.6–22.5(–24) microns long. Microhair apical cell/total length ratio 0.34–0.47. Stomata common; 24–27 microns long. Subsidiaries triangular. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells common; in cork/silica-cell pairs, or not paired (solitaries and triplets); silicified, or not silicified. Intercostal silica bodies when present, cross-shaped, or saddle shaped. Costal short-cells conspicuously in long rows. Costal silica bodies ‘panicoid-type’; dumb-bell shaped, or nodular.

Transverse section of leaf blade, physiology. C4; XyMS–. PCR cell chloroplasts with reduced grana; centrifugal/peripheral. Mesophyll with radiate chlorenchyma; traversed by columns of colourless mesophyll cells (rarely), or not traversed by colourless columns. Leaf blade adaxially flat. Midrib conspicuous; having a conventional arc of bundles. Bulliforms present in discrete, regular adaxial groups; associated with colourless mesophyll cells to form deeply-penetrating fans (sometimes linked to the abaxial epidermis by colourles cells); associating with colourless mesophyll cells to form arches over small vascular bundles. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present; nowhere forming ‘figures’. Sclerenchyma all associated with vascular bundles, or not all bundle-associated.

Phytochemistry. Leaves without flavonoid sulphates (2 species).

Cytology. Chromosome base number, x = 5 and 10. 2n = 20, 40, 50, and 60. Chromosomes ‘small’.

Classification. Watson & Dallwitz (1994): Panicoideae; Andropogonodae; Andropogoneae; Andropogoninae. Soreng et al. (2015): Panicoideae; Andropogonodae; Andropogoneae. 8 species.

Distribution, phytogeography, ecology. Tropical and subtropical.

Commonly adventive (I. cylindrica being one of the world’s worst weeds). Helophytic, or mesophytic, or xerophytic; species of open habitats; halophytic, or glycophytic. Often in damp or weedy places, some forms of I. cylindrica in coastal sand.

Economic aspects. Significant weed species: I. brasiliensis, I. cylindrica. I. cylindrica var. major cultivated for papermaking.

Hybrids. Intergeneric hybrids procured with Saccharum.

Rusts and smuts. Rusts — Puccinia. Taxonomically wide-ranging species: Puccinia microspora and Puccinia miscanthae. Smuts from Ustilaginaceae. Ustilaginaceae — Sphacelotheca and Ustilago.

References, etc. Leaf anatomical: Metcalfe 1960; studied by us - I. cylindrica (L.) Beauv.

Illustrations. • I. cylindrica: Gardner, 1952. • I. cylindrica, as I. arundinacea: Wood, Natal Plants 2 (1904). • General aspect (I. cylindrica): Gibbs Russell et al., 1990. • Inflorescence detail (I. cylindrica). Imperata cylindrica. Silvery-silky hairs from the bases of glumes and callus. • Spikelet details of I. cylindrica. Imperata cylindrica. Lower glume. Proximal lemma (sterile, epaleate). Palea of upper floret. Upper glume. Upper lemma absent. Gynoecium with basally joined styles. • I. cylindrica, abaxial epidermis of leaf blade: this project. • I. cylindrica, abaxial epidermis of leaf blade: this project. • I. cylindrica, leaf blade TS of midrib region: this project. Imperata cylindrica. • I. cylindrica, T.S. leaf blade midrib zone: this project. • I. cylindrica, leaf blade T.S. details: this project. Imperata cylindrica. Minor bundles, one with over-arching bulliforms+colourless cells.

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.’.