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The grass genera of the world

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

Dichelachne Endl.

From the Greek dichelos (cloven-footed) and achne (chaff, scale), referring to bilobed lemmas.

Plumegrasses.

Type species: Type: D. montana Endl.

Habit, vegetative morphology. Annual, or perennial; caespitose. Culms 50–130 cm high; herbaceous; unbranched above. Culm nodes glabrous. Culm internodes hollow. Leaves not basally aggregated; non-auriculate. Leaf blades apically cucullate; narrow; not pseudopetiolate; without cross venation; persistent. Ligule an unfringed membrane; truncate; 2–4 mm long.

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

Inflorescence. Inflorescence paniculate; contracted; spicate, or more or less irregular. Primary inflorescence branches where known, borne distichously. Inflorescence espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets not secund; pedicellate; not in distinct ‘long-and-short’ combinations.

Female-fertile spikelets. Spikelets 5.5–9.5 mm long; compressed laterally; disarticulating above the glumes. Rachilla minutely prolonged beyond the uppermost female-fertile floret, or terminated by a female-fertile floret; the rachilla extension when present, naked. Hairy callus present. Callus short; blunt.

Glumes two; very unequal to more or less equal; (the upper) long relative to the adjacent lemmas (longer or slightly shorter than the floret); pointed (acuminate); awnless; carinate, or non-carinate; similar (hyaline to membranous). Lower glume 1 nerved. Upper glume 1(–3) nerved. Spikelets with female-fertile florets only; without proximal incomplete florets.

Female-fertile florets 1(–3). Lemmas linear to narrowly lanceolate; not convolute (involute); decidedly firmer than the glumes (the main, eqivocal distinction from Agrostis); not becoming indurated (thinly leathery); entire, or incised (tending to split); when incised, 2 lobed; not deeply cleft (no more than minutely notched); awned. Awns 1; median; from a sinus, or dorsal, or apical; from near the top; non-geniculate, or geniculate; usually recurving; much longer than the body of the lemma (usually 1.5–3 cm long); entered by one vein. Lemmas hairless; faintly 5 nerved. Palea present; relatively long; entire (acute); awnless, without apical setae; not indurated; 2-nerved; 2-keeled (furrowed). Lodicules present; free; membranous; glabrous; not toothed. Stamens 1–3. Anthers penicillate, or not penicillate. Ovary apically glabrous. Styles free to their bases. Stigmas 2; white.

Fruit, embryo and seedling. Fruit free from both lemma and palea; small; longitudinally grooved; compressed dorsiventrally. Hilum short, or long-linear. Embryo small; not waisted. Endosperm liquid in the mature fruit; with lipid; containing only simple starch grains. Embryo with an epiblast; without a scutellar tail; with a negligible mesocotyl internode. Embryonic leaf margins meeting.

First seedling leaf with a well-developed lamina.

Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells similar in shape costally and intercostally (narrow); differing markedly in wall thickness costally and intercostally (the costals thicker walled). Mid-intercostal long-cells fusiform; having straight or only gently undulating walls. Microhairs absent. Stomata absent or very rare, or common. Subsidiaries parallel-sided. Intercostal short-cells absent or very rare; usually in cork/silica-cell pairs; silicified, or not silicified. Intercostal silica bodies when present, rounded. Costal short-cells neither distinctly grouped into long rows nor predominantly paired. Costal silica bodies horizontally-elongated crenate/sinuous, or horizontally-elongated smooth, or rounded.

Transverse section of leaf blade, physiology. C3; XyMS+. PBS cells without a suberised lamella. Mesophyll with non-radiate chlorenchyma. Leaf blade with distinct, prominent adaxial ribs, or ‘nodular’ in section; with the ribs more or less constant in size. Midrib conspicuous, or not readily distinguishable; with one bundle only. Bulliforms present in discrete, regular adaxial groups (in the furrows); in simple fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present; nowhere forming ‘figures’. Sclerenchyma all associated with vascular bundles.

Culm anatomy. Culm internode bundles in one or two rings.

Special diagnostic feature. The upper part of the lemma without pappus-like hairs.

Cytology. Chromosome base number, x = 7. 2n = 70. 10 ploid.

Classification. Watson & Dallwitz (1994): Pooideae; Poodae; Aveneae. Soreng et al. (2015): Pooideae; Poodae; Poeae; Agrostidinae. 5 species.

Distribution, phytogeography, ecology. Australia, New Zealand, New Guinea, Timor, Pacific.

Mesophytic, or xerophytic; species of open habitats. Forest margins and upland grasslands.

Rusts and smuts. Rusts — Puccinia. Taxonomically wide-ranging species: Puccinia graminis.

References, etc. Morphological/taxonomic: Veldkamp 1974. Leaf anatomical: Metcalfe 1960; this project.

Special comments. Separable only with difficulty from Calamagrostis, Agrostis and Deyeuxia. Illustrations. • D. micrantha (as D. sciurea): Hooker, Fl. Tasmaniae (1860). • D. crinita: Gardner, 1952. • Inflorescence of D. micrantha


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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: 13th November 2017. delta-intkey.com/grass’.

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