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The grass genera of the world

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

Ammochloa Boiss.

From the Greek ammos (sand) and chloë (grass), re habitat.

Including Cephalochloa Coss. & Dur., Dictyochloa (Murbeck) E.G. Camus

Habit, vegetative morphology. Annual; caespitose. Culms 1–25 cm high; herbaceous; unbranched above. Culm internodes hollow. Leaves mostly basal; non-auriculate. Sheath margins free. Leaf blades linear to linear-lanceolate; narrow; 1–3 mm wide; flat, or rolled (convolute); without cross venation; persistent. Ligule an unfringed membrane; not truncate; 0.5–5 mm long.

Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. The spikelets of sexually distinct forms on the same plant; hermaphrodite and sterile (the latter reduced to small, sterile bracts at the base of the inflorescence); overtly heteromorphic.

Inflorescence. Inflorescence paniculate; contracted; capitate to more or less ovoid (reduced to a sub-globose head of close-packed spikelets); espatheate. Spikelet-bearing axes persistent. Spikelets associated with bractiform involucres (these representing basal, sterile spikelets); not secund; subsessile.

Female-fertile spikelets. Spikelets 4–9 mm long; compressed laterally; disarticulating above the glumes. Rachilla prolonged beyond the uppermost female-fertile floret; the rachilla extension naked. Hairy callus absent. Callus short.

Glumes two (ovate-oblique); more or less equal; shorter than the spikelets; long relative to the adjacent lemmas; pointed; awnless; carinate (sometimes narrowly winged); similar (papery to membranous). Lower glume 1–2 nerved. Upper glume 1–2 nerved. Spikelets with female-fertile florets only.

Female-fertile florets 4–12. Lemmas similar in texture to the glumes to decidedly firmer than the glumes (papery to membranous, becoming leathery); not becoming indurated; entire; pointed; mucronate (the mucro recurved); hairless; carinate; 5–7 nerved. Palea present; relatively long; entire to apically notched; awnless, without apical setae; not indurated (membranous); 2-nerved; 2-keeled. Lodicules absent. Stamens 2–3. Anthers 0.6–0.8 mm long; not penicillate. Ovary apically glabrous; with a conspicuous apical appendage (this membranous, associated with the styles), or without a conspicuous apical appendage. Styles fused. Stigmas 2.

Fruit, embryo and seedling. Fruit free from both lemma and palea; small to large (winged via the ovary appendage); compressed laterally, or not noticeably compressed. Hilum short. Embryo large, or small. Endosperm hard; with lipid. Embryo with an epiblast; without a scutellar tail; with a negligible mesocotyl internode. Embryonic leaf margins meeting.

Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells markedly different in shape costally and intercostally; of similar wall thickness costally and intercostally. Mid-intercostal long-cells fusiform; having straight or only gently undulating walls. Microhairs absent. Stomata common. Subsidiaries parallel-sided. Guard-cells overlapped by the interstomatals. Intercostal short-cells absent or very rare. Costal short-cells neither distinctly grouped into long rows nor predominantly paired. Costal silica bodies horizontally-elongated crenate/sinuous.

Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with non-radiate chlorenchyma; without adaxial palisade. Leaf blade adaxially flat. Midrib conspicuous (rounded keel with larger bundle); with one bundle only. Bulliforms not present in discrete, regular adaxial groups; nowhere involved in bulliform-plus-colourless mesophyll arches. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders absent (strands only). Sclerenchyma all associated with vascular bundles.

Cytology. Chromosomes ‘large’.

Classification. Watson & Dallwitz (1994): Pooideae; Poodae; Aveneae. Soreng et al. (2015): Pooideae; Poodae; Poeae; Ammochloinae. 3 species.

Distribution, phytogeography, ecology. Mediterranean.

Xerophytic; species of open habitats. Dry sandy places.

Rusts and smuts. Smuts from Tilletiaceae. Tilletiaceae — Tilletia.

References, etc. Leaf anatomical: studied by us - A. involucrata Murbeck, A. palestina Boiss.

Illustrations. • A. palaestina: Fl. Iraq, 1968

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.’.