| # 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.

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.

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; studied by us - D. micrantha (Cav.) Domin.

Special comments. Separable only with difficulty from Calamagrostis, Agrostis and Deyeuxia.

Illustrations. • Dichelachne micrantha (as D. sciurea): Hooker, Fl. Tasmaniae (1860). • Dichelachne crinita: Gardner, 1952. • Inflorescence of Dichelachne micrantha.

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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