| # The grass genera of the world |

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

### Erianthus Michx.

From the Greek erion (wool) and anthos (flower), alluding to woolly glumes.

~ Saccharum

Including Ripidium Trin.

Habit, vegetative morphology. Perennial; sometimes reedy (or reedlike); caespitose. Culms 200–400 cm high; unbranched above. Culm nodes glabrous. Culm internodes solid. Leaves not basally aggregated; non-auriculate. Leaf blades broad (always?); without cross venation; persistent. Ligule an unfringed membrane to a fringed membrane.

Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. The spikelets all alike in sexuality; homomorphic (save in glume nervation). Plants exposed-cleistogamous, or chasmogamous.

Inflorescence. Inflorescence paniculate (silky-hairy); open; espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes ‘racemes’; with very slender rachides; disarticulating; disarticulating at the joints. ‘Articles’ linear; not appendaged; disarticulating transversely; densely long-hairy (plumose), or 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 compressed dorsiventrally; falling with the glumes (the pedicelled member falling from its 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; awnless; very dissimilar (the lower bicarinate, the upper naviculate). Lower glume two-keeled; not pitted; relatively smooth; 2 nerved. Upper glume 3 nerved. Spikelets with incomplete florets. The incomplete florets proximal to the female-fertile florets. The proximal incomplete florets 1; epaleate; sterile. The proximal lemmas awnless; 1 nerved; more or less equalling the female-fertile lemmas; similar in texture to the female-fertile lemmas (thinly membranous); not becoming indurated.

Female-fertile florets 1. Lemmas less firm than the glumes (hyaline); not becoming indurated; entire, or incised; when entire pointed (to aristate), or blunt; not deeply cleft; mucronate, or awned. Awns 1; median; apical; non-geniculate; hairless; much shorter than the body of the lemma to much longer than the body of the lemma. Lemmas ciliate; non-carinate; 3 nerved. Palea present; (when present) conspicuous but relatively short, or very reduced; entire; 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 free from both lemma and palea; small. Hilum short. Endosperm hard; without lipid; containing compound starch grains. Embryo without an epiblast; with a scutellar tail; with an elongated mesocotyl internode. Embryonic leaf margins overlapping.

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; 42–54 microns long; 3.3–5.4 microns wide at the septum. Microhair total length/width at septum 8.5–13.8. Microhair apical cells (10–)19.5–25 microns long. Microhair apical cell/total length ratio 0.39–0.47. Stomata common; 24–25.5(–27) microns long. Subsidiaries triangular. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells absent or very rare; not paired (solitary); not silicified. Costal short-cells conspicuously in long rows. Costal silica bodies ‘panicoid-type’; cross shaped to dumb-bell shaped.

Transverse section of leaf blade, physiology. C4; XyMS–. PCR cell chloroplasts with reduced grana. Mesophyll with radiate chlorenchyma. Leaf blade with distinct, prominent adaxial ribs, or ‘nodular’ in section; 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; associating with colourless mesophyll cells to form arches over small vascular bundles, or nowhere involved in bulliform-plus-colourless mesophyll arches. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present; nowhere forming ‘figures’. Sclerenchyma all associated with vascular bundles.

Phytochemistry. Leaves containing flavonoid sulphates (E. maximus), or without flavonoid sulphates (8 species).

Cytology. Chromosome base number, x = 5 and 10. 2n = 10, 15, 20, 30, and 60. Chromosomes ‘small’.

Classification. Watson & Dallwitz (1994): Panicoideae; Andropogonodae; Andropogoneae; Andropogoninae. Soreng et al. (2015): Panicoideae; Andropogonodae; Andropogoneae; Saccharinae. 28 species.

Distribution, phytogeography, ecology. Tropical America, southeast Europe to eastern Asia, Indomalayan region, Polynesia, Sahara, Madagascar.

Helophytic, or mesophytic.

Hybrids. Intergeneric hybrids with Saccharum.

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

References, etc. Leaf anatomical: Metcalfe 1960; studied by us - E. fastigiatus (Nees ex Steud.) Stapf.

Illustrations. • Erianthus ravennae: Lamson-Scribner (1890). • Erianthus ravennae: Hitchcock and Chase (1950). • Erianthus fastigiatus, 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: 15th June 2025. delta-intkey.com’.

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