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; a fringed membrane.
Reproductive organization. Plants bisexual, with bisexual spikelets; with hermaphrodite florets.
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 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.
Taxonomy. Chloridoideae; main chloridoid assemblage.
Distribution, ecology, phytogeography. 6 species; North tropical Africa, tropical southwest Asia. Xerophytic; species of open habitats; halophytic, or glycophytic. Grassland, sand and semidesert.
Holarctic and Paleotropical. Tethyan. African and Indomalesian. Irano-Turanian. Saharo-Sindian and Sudano-Angolan. Indian. Sahelo-Sudanian and Somalo-Ethiopian.
References, etc. Morphological/taxonomic: Napper 1963. Leaf anatomical: Metcalfe 1960; this project; Van den Borre 1994.
Illustrations. • General aspect
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).
