Grass Genera of the World

L. Watson and M. J. Dallwitz


Coelachne R.Br.

From the Greek koilos (hollow) and achne (chaff, scale), referring to a ventricose lower lemma.

Habit, vegetative morphology. Low annual, or perennial; caespitose, or decumbent. Culms 4–50 cm high; herbaceous. Culm nodes glabrous. Leaves non-auriculate. Leaf blades linear to ovate-lanceolate; narrow; not pseudopetiolate; cross veined, or without cross venation; persistent; rolled in bud; a fringe of hairs.

Reproductive organization. Plants bisexual, with bisexual spikelets; with hermaphrodite florets.

Inflorescence. Inflorescence of spicate main branches, or paniculate; open, or contracted; with capillary branchlets, or without capillary branchlets. Primary inflorescence branches inserted all around the main axis. Inflorescence espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets solitary, or paired; not secund; pedicellate; not in distinct ‘long-and-short’ combinations.

Female-fertile spikelets. Spikelets ovate; not noticeably compressed to compressed dorsiventrally; disarticulating above the glumes; disarticulating between the florets; with distinctly elongated rachilla internodes between the florets. Rachilla terminated by a female-fertile floret; hairy. Hairy callus present, or absent.

Glumes two (persistent); very unequal to more or less equal; shorter than the spikelets (1/3 to 2/3 their length); shorter than the adjacent lemmas; hairless (usually glabrous); not pointed (obtuse); awnless; non-carinate; similar (broad, membranous). Lower glume 1–5 nerved. Upper glume 3–7 nerved. Spikelets with female-fertile florets only (but the upper floret female-only); without proximal incomplete florets.

Female-fertile florets 2 (these dissimilar, separated by a slender rachilla segment). Lemmas saccate (sometimes, the lower), or not saccate; decidedly firmer than the glumes (the lower becoming somewhat hardened, the upper remaining membranous); smooth; not becoming indurated; white in fruit; entire; blunt; awnless (obtuse); hairy (L2 usually pubescent), or hairless (L1 basally hairy or not); non-carinate; with a clear germination flap; 0 nerved. Palea present; entire (obtuse); awnless, without apical setae; 2-nerved. Lodicules present; 2; free; fleshy; glabrous. Stamens 2–3. Anthers not penicillate. Ovary glabrous. Styles fused, or free to their bases. Stigmas 2.

Fruit, embryo and seedling. Fruit free from both lemma and palea; small; compressed dorsiventrally. Hilum short. Embryo large, or small; not waisted. Endosperm hard.

Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae present, or absent. Intercostal papillae over-arching the stomata, or not over-arching the stomata; consisting of one symmetrical projection per cell (but not on every cell). Long-cells markedly different in shape costally and intercostally (the costals short, irregularly shaped); of similar wall thickness costally and intercostally (thin walled). Intercostal zones without typical long-cells (the cells mainly more or less isodiametric). Mid-intercostal long-cells rectangular (hexagonal to square); having straight or only gently undulating walls. Microhairs present; more or less spherical, or elongated; ostensibly one-celled, or clearly two-celled; chloridoid-type (apical cell somewhat pointed, but thick walled and broader than long); (7–)13–38(–42) microns long. Microhair apical cells 7–24(–26) microns long. Microhair apical cell/total length ratio 0.64–0.73. Stomata common; 24–27 microns long. Subsidiaries parallel-sided to triangular; including both triangular and parallel-sided forms on the same leaf. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells absent or very rare; not paired; not silicified. Costal short-cells conspicuously in long rows. Costal silica bodies acutely-angled (more or less cubical); sharp-pointed.

Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with radiate chlorenchyma; Isachne-type. Leaf blade with distinct, prominent adaxial ribs, or ‘nodular’ in section; with the ribs more or less constant in size. Midrib not readily distinguishable; with one bundle only. Bulliforms present in discrete, regular adaxial groups (in the furrows, the groups sometimes inconspicuous); in simple fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present; forming ‘figures’, or nowhere forming ‘figures’. Sclerenchyma all associated with vascular bundles.

Cytology. Chromosome base number, x = 10. 2n = 40.

Taxonomy. Panicoideae; Panicodae; Isachneae.

Distribution, ecology, phytogeography. 10 species; palaeotropical. Helophytic; species of open habitats; glycophytic. Streamsides and marshes.

Holarctic, Paleotropical, and Australian. Boreal. African, Madagascan, and Indomalesian. Eastern Asian. Sudano-Angolan. Indian, Indo-Chinese, Malesian, and Papuan. North and East Australian. Somalo-Ethiopian and South Tropical African. Tropical North and East Australian.

References, etc. Leaf anatomical: Metcalfe 1960; this project.

Illustrations. • Abaxial epidermis of leaf blade. • Abaxial epidermis of leaf blade. Coelachne pulchella.


Cite this publication as: Watson, L., and Dallwitz, M. J. (1992 onwards). ‘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.’ http://biodiversity.uno.edu/delta/. Version: 18th August 1999. Dallwitz (1980), Dallwitz, Paine and Zurcher (1993 onwards, 1998), and Watson and Dallwitz (1994), and Watson, Dallwitz, and Johnston (1986) should also be cited (see References).

Index