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The grass genera of the world

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

Coelachyrum Hochst. & Nees

Including Coeleochloa Steud.

Excluding Coelachyropsis, Cypholepis

Habit, vegetative morphology. Annual, or perennial; usually stoloniferous. Culms 15–100 cm high; herbaceous. Leaves non-auriculate. Leaf blades narrow; flat; without abaxial multicellular glands; without cross venation. Ligule a fringed membrane.

Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets; without hidden cleistogenes.

Inflorescence. Inflorescence of spicate main branches (slender racemes), or paniculate; digitate, or non-digitate; espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets secund (the racemes unilateral), or not secund; biseriate; shortly pedicellate.

Female-fertile spikelets. Spikelets 5–7 mm long; compressed laterally; disarticulating above the glumes; disarticulating between the florets; with conventional internode spacings. Rachilla prolonged beyond the uppermost female-fertile floret. Hairy callus absent. Callus absent.

Glumes two; very unequal to more or less equal; shorter than the adjacent lemmas, or long relative to the adjacent lemmas; lateral to the rachis; awnless; similar (somewhat carinate, lanceolate). Lower glume 1 nerved, or 3 nerved. Upper glume 3 nerved. Spikelets with female-fertile florets only, or with incomplete florets. The incomplete florets distal to the female-fertile florets. Spikelets without proximal incomplete florets.

Female-fertile florets 2–10. Lemmas saccate (below); not becoming indurated (membranous or scarious); awnless to mucronate; hairy, or hairless; lightly carinate, or non-carinate (as the fruit expands); 3 nerved. Palea present (broadly oval); entire; awnless, without apical setae; membranous; 2-nerved; 2-keeled (with narrow margins). 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 (1.75–2 mm long); ellipsoid to subglobose (sub-orbicular); compressed dorsiventrally (concavo-convex); sculptured. Hilum short. Pericarp free. Embryo large; not waisted.

Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Mid-intercostal long-cells rectangular; having markedly sinuous walls, or having straight or only gently undulating walls. Microhairs present; more or less spherical; ostensibly one-celled, or clearly two-celled (?); chloridoid-type. Microhair apical cells 6–11 microns long. Stomata common. Subsidiaries low dome-shaped and triangular. Intercostal short-cells absent or very rare; not paired. Intercostal silica bodies absent. Costal short-cells conspicuously in long rows. Costal silica bodies present in alternate cell files of the costal zones; saddle shaped, or oryzoid, or ‘panicoid-type’; sometimes cross shaped, or butterfly shaped.

Transverse section of leaf blade, physiology. Lamina mid-zone in transverse section open.

C4; XyMS+. PCR sheaths of the primary vascular bundles complete. PCR sheath extensions absent. Mesophyll with radiate chlorenchyma; traversed by columns of colourless mesophyll cells. Leaf blade ‘nodular’ in section; with the ribs more or less constant in size. Midrib conspicuous; with one bundle only. Bulliforms present in discrete, regular adaxial groups; in simple fans and associated with colourless mesophyll cells to form deeply-penetrating fans (the simple groups each with a large, deeply-penetrating median cell). All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present. Sclerenchyma all associated with vascular bundles. The lamina margins with fibres.

Classification. Watson & Dallwitz (1994): Chloridoideae; main chloridoid assemblage. Soreng et al. (2015): Chloridoideae; Cynodonteae; Eleusininae. 6 species.

Distribution, phytogeography, ecology. North tropical Africa, tropical southwest Asia.

Xerophytic; species of open habitats; halophytic, or glycophytic. Grassland, sand and semidesert.

References, etc. Morphological/taxonomic: Napper 1963. Leaf anatomical: Metcalfe 1960; studied by us - Coelachyrum poaeflorum Chiov.; Van den Borre 1994.

Illustrations. • C. yemenicum: Gibbs Russell et al., 1990

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: 11th December 2017.’.