The grass genera of the world
Habit, vegetative morphology. Perennial; stoloniferous, or caespitose. Culms 20–60 cm high; herbaceous; unbranched above; 1 noded. Culm nodes hidden by leaf sheaths. Young shoots intravaginal. Leaves mostly basal; non-auriculate; without auricular setae. Leaf blades linear to lanceolate; narrow; about 4 mm wide; rolled; not pseudopetiolate; without cross venation; persistent. Ligule an unfringed membrane (but ciliolate); truncate; about 0.5–1 mm long. Contra-ligule absent.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets.
Inflorescence. Inflorescence a single spike (tough). Rachides hollowed. Inflorescence espatheate; not comprising partial inflorescences and foliar organs. Spikelets solitary; not secund; distichous; sessile; not imbricate.
Female-fertile spikelets. Spikelets 5–9 mm long; compressed laterally to not noticeably compressed; disarticulating above the glumes; disarticulating between the florets. Rachilla prolonged beyond the uppermost female-fertile floret; the rachilla extension with incomplete florets. Hairy callus absent. Callus short; blunt (glabrous).
Glumes two; more or less equal; shorter than the spikelets; long relative to the adjacent lemmas; free; lateral to the rachis; hairless; glabrous; fairly not pointed; awnless; non-carinate; similar. Lower glume 3–5 nerved. Upper glume 3–5 nerved. Spikelets with incomplete florets. The incomplete florets distal to the female-fertile florets. The distal incomplete florets 1; merely underdeveloped; awnless.
Female-fertile florets 2–4(–6). Lemmas ovate; less firm than the glumes (somewhat cartilaginous); not becoming indurated; entire; awnless; hairless; glabrous; non-carinate (rounded on the back); without a germination flap; 3 nerved (lower florets), or 5 nerved (upper florets, in the material seen); with the nerves non-confluent. Palea present; relatively long (lanceolate); tightly clasped by the lemma; entire, or apically notched; awnless, without apical setae; textured like the lemma (membranous); 2-nerved; 2-keeled. Palea keels wingless; hairy. Lodicules present; 2; free; membranous; not toothed; not or scarcely vascularized. Stamens 3. Ovary apically glabrous; with a conspicuous apical appendage (this fleshy, glabrous). Styles free to their bases. Stigmas 2.
Fruit, embryo and seedling. Fruit free from both lemma and palea; small (2–3 mm long); fusiform; compressed dorsiventrally. Hilum short (shortly linear). Embryo small. Endosperm hard.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells markedly different in shape costally and intercostally (the costals much narrower); of similar wall thickness costally and intercostally (the walls of medium thickness). Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs absent. Stomata common. Subsidiaries non-papillate; high dome-shaped and triangular. Guard-cells slightly overlapped by the interstomatals, or overlapping to flush with the interstomatals. Intercostal short-cells common; consistently in cork/silica-cell pairs; silicified. Intercostal silica bodies rounded. Costal silica bodies horizontally-elongated crenate/sinuous and horizontally-elongated smooth (a mixture of short-crenate forms and potato shapes).
Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll without adaxial palisade. Leaf blade with distinct, prominent adaxial ribs; with the ribs more or less constant in size (these broad, flat-topped). Midrib conspicuous (by its large bundle, a fairly prominent, rounded keel and large bulliform hinges); with one bundle only; without colourless mesophyll adaxially. The lamina symmetrical on either side of the midrib. Bulliforms present in discrete, regular adaxial groups; in simple fans (one at the base of each furrow). All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present (with all the large bundles); forming figures (mostly Is, the midrib with a large anchor). Sclerenchyma all associated with vascular bundles (apart from large groups in the blade margins).
Classification. Watson & Dallwitz (1994): Pooideae; Poodae; Poeae. Soreng et al. (2015): Pooideae; Poodae; Poeae; Parapholiinae. 2 species.
Distribution, phytogeography, ecology. North Africa, Cape Verde Islands.
Halophytic (in damp, saline soils).
References, etc. Leaf anatomical: this project.
Illustrations. • Spikelet of A. lolium. • Spikelet of A. lolium (2). • Spike of A. lolium. • Caryopsis of A. lolium. • A. lolium, abaxial epidermis 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’.