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The grass genera of the world

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

Saccharum L.

From the Latin saccharum (sugar).

Including Rhipidium Trin., Saccharifera Stokes, Tripidium

Excluding Erianthus, Miscanthus, Lasiorhachis, Narenga

Habit, vegetative morphology. Robust perennial (cane grasses); not reedy; rhizomatous. Culms 150–1200 cm high; woody and persistent, or herbaceous; often unbranched. Culm nodes glabrous. Culm internodes solid. Leaves not basally aggregated; auriculate, or non-auriculate. Leaf blades usually linear; broad, or narrow; 10–40(–60) mm wide (to 60 cm in S. officinarum); flat; 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. Plants outbreeding. Apomictic, or reproducing sexually.

Inflorescence. Inflorescence paniculate; open (plumose, silvery); espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes spiciform ‘racemes’; with very slender rachides; disarticulating; disarticulating at the joints. ‘Articles’ linear; without a basal callus-knob; not appendaged; disarticulating transversely; densely long-hairy to somewhat hairy. Spikelets paired; 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 hermaphrodite.

Female-fertile spikelets. Spikelets 2–6 mm long (the pedicellate and sessile members similar); compressed laterally, or not noticeably compressed, or compressed dorsiventrally; falling with the glumes (the pedicelled falling from the pedicel, the sessile falling with the joint and pedicel). Rachilla terminated by a female-fertile floret. Hairy callus present.

Glumes two; more or less equal; long relative to the adjacent lemmas; without conspicuous tufts or rows of hairs; awnless; very dissimilar (the sessile spikelet with the lower bicarinate, the upper imparinerved), or similar (the pedicellate spikelet with both imparinerved). Lower glume more or less two-keeled (in sessile spikelets), or not two-keeled (in pedicellate spikelets); convex on the back, or flattened on the back; not pitted; relatively smooth. Spikelets with incomplete florets. The incomplete florets proximal to the female-fertile florets. Spikelets with proximal incomplete florets. The proximal incomplete florets 1; paleate, or epaleate. Palea of the proximal incomplete florets fully developed, or reduced. The proximal incomplete florets sterile. The proximal lemmas awnless; not becoming indurated.

Female-fertile florets 1. Lemmas membranous, or reduced to a linear stipe; less firm than the glumes; not becoming indurated; entire; pointed, or blunt; mucronate, or awned. Awns 1 (bristle-like); median; apical; non-geniculate. Lemmas hairy; 0–1 nerved. Palea present, or absent; when present, relatively long, or conspicuous but relatively short, or very reduced; awnless, without apical setae; not indurated (hyaline); nerveless. Lodicules present; free; fleshy; ciliate; toothed (with a blunt tooth, or one on each margin). Stamens 3. Ovary apically glabrous. Styles fused. Stigmas 2; red pigmented.

Fruit, embryo and seedling. Fruit free from both lemma and palea; not noticeably compressed (terete). Hilum short. Embryo large, or small.

Seedling with a long mesocotyl.

Abaxial leaf blade epidermis. Papillae present, or absent. Intercostal papillae over-arching the stomata. Mid-intercostal long-cells having markedly sinuous walls. Microhairs present; panicoid-type; (48–)51–72(–78) microns long; (4.5–)6–9(–9.6) microns wide at the septum. Microhair total length/width at septum 8.5–12. Microhair apical cells (16–)20–53(–63) microns long. Microhair apical cell/total length ratio 0.4–0.7. Stomata common; (33–)35–42(–45) microns long. Subsidiaries low dome-shaped to triangular. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells common, or absent or very rare; when present, silicified. Intercostal silica bodies when present, cross-shaped. Costal short-cells predominantly paired, or neither distinctly grouped into long rows nor predominantly paired. Costal silica bodies ‘panicoid-type’; cross shaped to nodular; not sharp-pointed.

Transverse section of leaf blade, physiology. C4; biochemical type NADP–ME (S. officinarum); XyMS–. PCR cell chloroplasts with reduced grana; centrifugal/peripheral. Mesophyll with radiate chlorenchyma; traversed by columns of colourless mesophyll cells, or not traversed by colourless columns. Leaf blade with distinct, prominent adaxial ribs, or ‘nodular’ in section, or adaxially flat; with the ribs very irregular in sizes. Midrib conspicuous; having a conventional arc of bundles; with colourless mesophyll adaxially. Bulliforms present in discrete, regular adaxial groups; in simple fans, or associated with colourless mesophyll cells to form deeply-penetrating fans (sometimes linked with traversing colourless tissue); associating with colourless mesophyll cells to form arches over small vascular bundles, or nowhere involved in bulliform-plus-colourless mesophyll arches. Many of the smallest vascular bundles unaccompanied by sclerenchyma. Combined sclerenchyma girders present; forming ‘figures’. Sclerenchyma all associated with vascular bundles.

Culm anatomy. Culm internode bundles scattered.

Phytochemistry. Leaves containing flavonoid sulphates (5 species), or without flavonoid sulphates (S. officinarum).

Cytology. Chromosome base number, x = 10 and 12. 2n = 40, or 60, or 68, or 76–78, or 80, or 90, or 46–128, or 110, or 112, or 116–117, or 144. 4, 6, 8, 9, and 12 ploid. Chromosomes ‘small’. Haploid nuclear DNA content 1.1–1.3 pg (3 species, one 6x and two 8x).

Classification. Watson & Dallwitz (1994): Panicoideae; Andropogonodae; Andropogoneae; Andropogoninae. Soreng et al. (2015): Panicoideae; Andropogonodae; Andropogoneae; Saccharinae. 5 species.

Distribution, phytogeography, ecology. Tropical, subtropical.

Helophytic, or mesophytic; shade species, or species of open habitats. Mostly riversides and valleys, some on open hillsides.

Economic aspects. Cultivated fodder: S. officinarum. Stems of S. spontaneum used for light construction work.

Hybrids. Intergeneric hybrids with Erianthus, Imperata, Miscanthidium, Miscanthus, Narenga, Sclerostachya, Sorghum; a claim involving Zea is probably erroneous, and one involving Bambusa has been proven so.

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

References, etc. Leaf anatomical: Metcalfe 1960, and studied by us.

Illustrations. • S. ravennae: Fl. Iraq, 1968. • S. villosum (as Erianthis trinii): Nicora & Rúgolo de Agrasar (1987). • S. robustum, abaxial epidermis of leaf blade: this project. • Pollen antigens: Watson and Knox (1976). • Pollen antigens: cross-reactions against anti-Lolium serum. • Pollen antigens: cross-reactions against anti-Lolium serum. • Heat stable pollen antigens (allergens): cross-reactions against anti-Lolium serum. • Pollen antigens: cross-reactions against anti-Cynodon serum. • Pollen antigens: cross-reactions against anti-Zea serum. • Pollen antigens: cross-reactions against anti-Zea serum

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.’.