| # The grass genera of the world |

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

### Eriachne R.Br.

From the Greek erion (wool) and achne (a scale), alluding to cataphylls (or lemmas?).

Wanderrie grasses.

Including Achneria P. Beauv., Massia Bal.

Habit, vegetative morphology. Annual, or perennial; rhizomatous, or caespitose. Culms 5–100 cm high; herbaceous; sparsely to amply branched above, or unbranched above. The branching simple, or fastigiate. Culms tuberous (rarely), or not tuberous. Culm nodes hairy, or glabrous. Culm internodes solid, or hollow. Leaves not basally aggregated; non-auriculate. Leaf blades narrow; often more or less setaceous; flat, or rolled (sometimes pungent); without cross venation; persistent; once-folded in bud. Ligule a fringe of hairs. Contra-ligule present (of hairs), or absent.

Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets; exposed-cleistogamous, or chasmogamous.

Inflorescence. Inflorescence paniculate, or a single raceme (rarely); open, or contracted; sometimes spicate; espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets solitary; not secund; pedicellate.

Female-fertile spikelets. Spikelets 2–15 mm long; compressed laterally to compressed dorsiventrally; disarticulating above the glumes; not disarticulating between the florets, or disarticulating between the florets; with conventional internode spacings. Rachilla prolonged beyond the uppermost female-fertile floret (rarely), or terminated by a female-fertile floret; the rachilla extension (when present) with incomplete florets. Hairy callus present. Callus short; blunt.

Glumes two; more or less equal; shorter than the spikelets to exceeding the spikelets; shorter than the adjacent lemmas, or long relative to the adjacent lemmas; awned, or awnless; carinate (rarely), or non-carinate (usually, rounded on the back); similar (persistent, broad, scarious to subhyaline or cartilaginous). Lower glume (7–)9–15 nerved. Upper glume (7–)9–15 nerved. Spikelets with female-fertile florets only, or with incomplete florets. The incomplete florets distal to the female-fertile florets (i.e. the upper of the two florets sometimes reduced). Spikelets without proximal incomplete florets.

Female-fertile florets (1–)2. Lemmas similar in texture to the glumes to decidedly firmer than the glumes (scarious to cartilaginous); becoming indurated to not becoming indurated; entire, or incised; awnless, or mucronate, or awned. Awns when present, 1; from a sinus, or apical; non-geniculate; much shorter than the body of the lemma to much longer than the body of the lemma. Lemmas hairy (with long white hairs); carinate to non-carinate; having the margins inrolled against the palea; with a clear germination flap; 5–7 nerved. Palea present; entire (pointed), or apically notched; awnless, without apical setae, or with apical setae, or awned (sometimes with 1 or 2 apical setae or awns); textured like the lemma; indurated, or not indurated; 2-nerved; 2-keeled to keel-less (the lateral ‘keels’ blunt). Lodicules present; 2; free; fleshy; glabrous. Stamens (2–)3. Anthers not penicillate. Ovary apically glabrous. Styles free to their bases. Stigmas 2; white, or red pigmented.

Fruit, embryo and seedling. Fruit free from both lemma and palea; small, or medium sized, or large; ellipsoid; compressed dorsiventrally (plano-convex). Hilum long-linear. Embryo large, or small; waisted, or not waisted. Endosperm hard; containing only simple starch grains, or containing compound starch grains. Embryo without an epiblast; with a scutellar tail; with an elongated mesocotyl internode. Embryonic leaf margins slightly overlapping.

Seedling with a long mesocotyl; with a loose coleoptile. First seedling leaf with a well-developed lamina. The lamina broad; erect; 6–12 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. Microhairs present; panicoid-type; 45–68 microns long; (5.1–)5.4–9(–9.8) microns wide at the septum. Microhair total length/width at septum 5.7–11.7. Microhair apical cells 25.5–36(–44) microns long. Microhair apical cell/total length ratio 0.42–0.62. Stomata common; 19–48 microns long. Subsidiaries dome-shaped. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells common, or absent or very rare; in cork/silica-cell pairs, or not paired (solitary); silicified. Intercostal silica bodies oryzoid-type. Costal short-cells conspicuously in long rows. Costal silica bodies oryzoid, or ‘panicoid-type’; sharp-pointed (the oryzoid forms, sometimes), or not sharp-pointed.

Transverse section of leaf blade, physiology. C4; biochemical type NADP–ME (in all 5 species studied); XyMS+ (this XyMS/C4 type combination being extremely unusual). PCR sheath outlines uneven (usually), or even, or uneven to even. PCR sheath extensions present, or absent. Maximum number of extension cells when present, 1–3. PCR cells without a suberised lamella. PCR cell chloroplasts ovoid; with well developed grana; usually centrifugal/peripheral, or centripetal (e.g. E. pulchella). Mesophyll with radiate chlorenchyma, or with non-radiate chlorenchyma. Leaf blade with distinct, prominent adaxial ribs, or ‘nodular’ in section; with the ribs more or less constant in size, or with the ribs very irregular in sizes. Midrib not readily distinguishable; with one bundle only, or having a conventional arc of bundles (rarely). Bulliforms present in discrete, regular adaxial groups (in the furrows); in simple fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present; forming ‘figures’. Sclerenchyma all associated with vascular bundles.

Phytochemistry. Leaf blade chlorophyll a:b ratio 4.12–5.

Classification. Watson & Dallwitz (1994): Arundinoideae (or Panicoideae); Eriachneae. Soreng et al. (2015): Micrairoideae; Eriachneae. 40 species.

Distribution, phytogeography, ecology. China, Indomalayan region, Australia.

Species of open habitats. Savanna.

Rusts and smuts. Smuts from Ustilaginaceae. Ustilaginaceae — Sorosporium.

References, etc. Morphological/taxonomic: Van Eck-Borsboom 1980. Leaf anatomical: Metcalfe 1960; studied by us - E. anomala Hartley, E. aristidea F. Muell., E. glabrata (Maiden) Hartley, E. mucronata R. Br., E. nervosa Ewart & Cookson, E. obtusa R. Br., E. ovata Nees, E. pulchella Domin.

Illustrations. • Eriachne capillaris: Kunth (1835). • Eriachne glauca: Kunth (1835). • Eriachne aristidea: Gardner, 1952. • Eriachne ciliata: E. Hickman. • Inflorescence, spikelets (Eriachne aristidea, E. helmsii, E. melicacea, E. ovata). • Spikelet of Eriachne ovata. • Opened spikelet of Eriachne ovata. • 2-floreted spikelet of Eriachne ovata with glumes removed: this project. Eriachne triseta. A two-floreted spikelet, each floret with an apically-awned lemma and two-awned palea. • Lemma and palea of Eriachne triseta. Eriachne triseta. Lemma (left) and palea. • Detail of spikelet tip (E. ovata). Eriachne ovata. Palea tip (left) with two apical setae, and apiculate lemma. • Caryopsis of Eriachne melicacea. • Germination flap (Eriachne ovata). • Germinating Eriachne ovata: this project. Eriachne ovata. Germination flap, and (left) radicle emerging. • Seedling of Eriachne ovata: this project. • Eriachne aristidea, leaf blade T.S. with PCR sheath details: original. Eriachne aristidea. XyMS+ (see primary bundle to right), but C4 type NADP-ME.

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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