The grass genera of the world
Type species: Type: A. arundinacea Host, nom. illeg. = A. arenaria (L.) Link.
Including Psamma P. Beauv.
Habit, vegetative morphology. Perennial; rhizomatous. Culms 20–130 cm high; herbaceous; unbranched above. Culm nodes glabrous. Culm internodes hollow. Leaves mostly basal; non-auriculate. Leaf blades linear; apically cucullate; narrow; 2–5 mm wide (sharp-pointed, blue-green); rolled (convolute); not pseudopetiolate; without cross venation; persistent; rolled in bud. Ligule an unfringed membrane; not truncate; 1–30 mm long.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets.
Inflorescence. Inflorescence paniculate; contracted; spicate. Primary inflorescence branches inserted all around the main axis. Inflorescence espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes persistent. Spikelets not secund; pedicellate.
Female-fertile spikelets. Spikelets 9–15 mm long; compressed laterally; disarticulating above the glumes. Rachilla prolonged beyond the uppermost female-fertile floret; hairy; the rachilla extension naked. Hairy callus present. Callus short; pointed.
Glumes two; more or less equal; about equalling the spikelets to exceeding the spikelets; long relative to the adjacent lemmas (exceeding them); pointed; awnless; carinate; similar. Lower glume 1 nerved. Upper glume 1–3 nerved. Spikelets with female-fertile florets only; without proximal incomplete florets.
Female-fertile florets 1. Lemmas similar in texture to the glumes; not becoming indurated; entire, or incised; when incised, 2 lobed; not deeply cleft; minutely awned, or mucronate. Awns 1; median; dorsal; from near the top (subterminal); non-geniculate; much shorter than the body of the lemma; entered by one vein. Lemmas hairless; carinate; without a germination flap; 3 nerved, or 5 nerved; with the nerves non-confluent. Palea present; relatively long; apically notched (minutely); awnless, without apical setae; not indurated (firm); several nerved (often 4-nerved); keel-less. Lodicules present; 2; free; membranous; ciliate, or glabrous; not toothed; not or scarcely vascularized. Stamens 3; with free filaments. Anthers 4–5 mm long; not penicillate. Ovary apically glabrous. Styles free to their bases. Stigmas 2.
Fruit, embryo and seedling. Fruit medium sized; ellipsoid; longitudinally grooved; compressed dorsiventrally, or not noticeably compressed. Hilum long-linear (two thirds of the fruit length). Embryo small. Endosperm hard; with lipid; containing compound starch grains. Embryo with an epiblast; without a scutellar tail; with a negligible mesocotyl internode. Embryonic leaf margins meeting.
Seedling with a tight coleoptile.
Abaxial leaf blade epidermis. Costal/intercostal zonation lacking. Papillae absent. Long-cells similar in shape costally and intercostally; of similar wall thickness costally and intercostally (walls thick, pitted). Mid-intercostal long-cells rectangular; having markedly sinuous walls, or having straight or only gently undulating walls (different from one specimen to another). Microhairs absent. Stomata absent or very rare. Intercostal short-cells common; not paired; not silicified. Costal short-cells neither distinctly grouped into long rows nor predominantly paired (mainly solitary, a few paired). Costal silica bodies absent to poorly developed; in so far as recognisable horizontally-elongated crenate/sinuous (poorly developed, but the silica-cells mainly square, elongated-sinuous or elongated-crenate).
Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with non-radiate chlorenchyma. Leaf blade with distinct, prominent adaxial ribs; with the ribs very irregular in sizes. Midrib not readily distinguishable; with one bundle only. Bulliforms not present in discrete, regular adaxial groups; in the furrows, in ill defined groups of small, irregularly sized cells. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present; forming figures (each bundle with a large anchor - the mesophyll being confined to lateral blocks in the ribs, and immediately beneath the furrows). Sclerenchyma not all bundle-associated (a continuous abaxial layer, linking with the anchors). The extra sclerenchyma in a continuous abaxial layer.
Cytology. Chromosome base number, x = 7. 2n = 14, 28, and 56. 2, 4, and 8 ploid. Chromosomes large.
Classification. Watson & Dallwitz (1994): Pooideae; Poodae; Aveneae. Soreng et al. (2015): Pooideae; Poodae; Poeae; Agrostidinae. 2 species.
Distribution, phytogeography, ecology. North temperate.
Commonly adventive. Xerophytic; species of open habitats; halophytic. Sand-binding and dune stabilizing.
Economic aspects. A. arenaria and ×Ammocalamagrostis widely used as sand stabilizers.
Hybrids. A. arenaria hybridizes with Calamagrostis epigejos (×Ammocalamagrostis P. Fourn.; ×Calamophila O. Schwartz = ×Ammocalamagrostis, ×Calammophila Brand = ×Ammocalamagrostis).
Rusts and smuts. Rusts Puccinia. Taxonomically wide-ranging species: Puccinia graminis, Puccinia coronata, and Puccinia pygmaea. Smuts from Ustilaginaceae. Ustilaginaceae Ustilago.
References, etc. Leaf anatomical: Metcalfe 1960; this project.
Illustrations. • A. arenaria: Gardner, 1952. • A. arenaria: Gibbs Russell et al., 1990. • A. arenaria (as Psammagrostis): Eng. Bot. (1872). • A. arenaria, abaxial epidermis of leaf blade: this project. • A. arenaria, transverse section of leaf blade: this project. • A. arenaria, transverse section of leaf blade: this project. • A. arenaria, transverse section of leaf blade: this project
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: 13th November 2017. delta-intkey.com/grass’.