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The grass genera of the world

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

Vetiveria Bory

From Tamil vetti (khus-khus or cus-cus) and ver (root), alluding to aromatic roots.

~ Chrysopogon

Including Mandelorna Steud., Lenormandia Steud.

Habit, vegetative morphology. Perennial (often with aromatic roots); forming large clumps from stout rhizomes. Culms 50–300 cm high; herbaceous; unbranched above. Culm nodes glabrous. Culm internodes solid. The shoots aromatic, or not aromatic (?). Leaves mostly basal; non-auriculate. Sheath margins free. The lower sheaths compressed. Leaf blades linear; broad, or narrow; without cross venation; persistent. Ligule a fringed membrane to a fringe of hairs.

Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. The spikelets of sexually distinct forms on the same plant; hermaphrodite and male-only, or hermaphrodite and sterile; homomorphic; all in heterogamous combinations.

Inflorescence. Inflorescence of spicate main branches, or paniculate (a panicle with slender, whorled, simple or rarely compound racemes); open; espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes ‘racemes’; the spikelet-bearing axes with 2–3 spikelet-bearing ‘articles’ to with 6–10 spikelet-bearing ‘articles’, or with more than 10 spikelet-bearing ‘articles’ (typically with many spikelet pairs); with very slender rachides; disarticulating; disarticulating at the joints. ‘Articles’ linear; not appendaged; disarticulating transversely. Spikelets paired; secund (rarely), or not secund; sessile and pedicellate; consistently in ‘long-and-short’ combinations; in pedicellate/sessile combinations. Pedicels of the ‘pedicellate’ spikelets free of the rachis. The ‘shorter’ spikelets hermaphrodite. The ‘longer’ spikelets male-only, or sterile.

Female-sterile spikelets. The pedicelled, male spikelets similar to the sessile ones, or slightly smaller.

Female-fertile spikelets. Spikelets 4.5–10 mm long; compressed laterally; falling with the glumes (and with the joint and pedicel). Rachilla terminated by a female-fertile floret. Hairy callus present, or absent. Callus pointed to blunt.

Glumes two; more or less equal; long relative to the adjacent lemmas; awned (G2, sometimes), or awnless; very dissimilar (the lower rounded on the back, the upper naviculate). Lower glume convex on the back; not pitted; spinulose; 5 nerved. Upper glume 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 awnless; 2 nerved; similar in texture to the female-fertile lemmas (hyaline); not becoming indurated.

Female-fertile florets 1. Lemmas less firm than the glumes (hyaline); not becoming indurated; incised; not deeply cleft (bidentate); awnless, or mucronate, or awned. Awns when present, 1; from a sinus; geniculate; hairless (glabrous); much shorter than the body of the lemma to much longer than the body of the lemma. Lemmas hairless; non-carinate; 1–3 nerved. Palea present, or absent; when present, very reduced; apically notched; awnless, without apical setae; not indurated (hyaline); nerveless. Lodicules present; 2; free; fleshy; glabrous. Stamens 3. Anthers not penicillate. Ovary apically glabrous. Styles free to their bases. Stigmas 2.

Fruit, embryo and seedling. Fruit 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.

First seedling leaf with a well-developed lamina. The lamina broad; curved; 21–30 veined.

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 (the sinuosities very tight in V. elongata). Microhairs present; panicoid-type (but often balanoform - the thin walled apical cells quite broad and blunt); (39–)48–51(–54) microns long; 9–12.6 microns wide at the septum. Microhair total length/width at septum 3.8–5.5. Microhair apical cells (25–)27–30(–33) microns long. Microhair apical cell/total length ratio 0.55–0.63. Stomata common; 27–33 microns long. Subsidiaries low dome-shaped, or triangular. Guard-cells overlapped by the interstomatals (the interstomatal end walls very thickened in V. elongata). Intercostal short-cells common; in cork/silica-cell pairs; silicified. Intercostal silica bodies tall-and-narrow, or cross-shaped. Costal zones with short-cells. Costal short-cells predominantly paired. Costal silica bodies tall-and-narrow (exclusively, in V. elongata), or ‘panicoid-type’; cross shaped (in V. zizanioides); not sharp-pointed.

Transverse section of leaf blade, physiology. C4; XyMS–. PCR sheath outlines even. PCR cell chloroplasts with reduced grana; centrifugal/peripheral. Mesophyll with radiate chlorenchyma. Leaf blade adaxially flat. Midrib conspicuous; having a conventional arc of bundles; with colourless mesophyll adaxially (the adaxial mesophyll of the rest of the blade also extensively colourless in V. elongata, and with large intercellular lacunae in V. zizanioides). Bulliforms not present in discrete, regular adaxial groups (except in association with the midrib). Many of the smallest vascular bundles unaccompanied by sclerenchyma. Combined sclerenchyma girders present. Sclerenchyma all associated with vascular bundles.

Cytology. Chromosome base number, x = 5 and 10. 2n = 20 and 40. Nucleoli persistent.

Classification. Watson & Dallwitz (1994): Panicoideae; Andropogonodae; Andropogoneae; Andropogoninae. Soreng et al. (2015): Panicoideae; Andropogonodae; Andropogoneae. 10 species.

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

Helophytic; glycophytic. Floodplains and streambanks.

Economic aspects. Commercial essential oils: V. zizanioides (from the roots). V. zizanioides is valuable for hedging, and as a guard against soil erosion (it also ‘repels pests such as rats and snakes’ - O. Sattaur 1989, New Scientist 1664, 16–17).

Rusts and smuts. Smuts from Tilletiaceae and from Ustilaginaceae. Tilletiaceae — Tilletia. Ustilaginaceae — Ustilago.

References, etc. Leaf anatomical: Metcalfe 1960; studied by us - V. elongata (R. Br.) Stapf ex C.E. Hubbard.

Illustrations. • V. pauciflora: Gardner, 1952. • General aspect (V. nigritana): Gibbs Russell et al., 1990. • V. elongata, abaxial epidermis of leaf blade: 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: 11th December 2017.’.